Scientific Studies about Effects of Breastfeeding

vs. Effects of Bottle Feeding

(updated Aug. 24, 2021)

There is considerable disagreement among published studies regarding effects of breastfeeding vs. effects of formula or bottle feeding.  It is typical for various scientific studies to arrive at opposite conclusions; this is especially true of studies that are of the "observational" type, which almost all of the studies dealing with this subject matter are.  The U.S. Surgeon General has pointed out the above fact regarding the nature of these studies in her "Surgeon General's Call to Action to Support Breastfeeding 2011," (p. 33) ⁽¹⁾ It is well known that observational studies are subject to false conclusion, since they do not have the randomized selection of study groups that helps avoid effects of confounders that can be the real causes of associations that are found.  Such studies would find sunshine in Florida to be "associated" with high death rates; confounders (such as the advanced average age in Florida) are often not considered in such studies.  Or if they are considered, it may well not be possible to properly deal with confounders -- the Users’ Guide to the Medical Literature of the American Medical Association merely says that false conclusions are to be expected in observational studies, and it doesn’t hold out hope that the low quality of evidence from observational studies could be greatly improved by adjustments or controls.⁽²⁾

By contrast, effects of confounders can be avoided or greatly minimized by means of the following:

a) randomized, controlled trials; for examples of that kind of study, see Section 2.b.2 below for one that found child obesity to be far higher among more-breastfed children than among less-breastfed children, the Kramer et al. study in Section 2.c.2 which found no beneficial effects of prolonged and exclusive breastfeeding on asthma or allergy, and the Perkin et al. study also in Section 2.c.2 which found that exclusive breastfeeding appears to result in far higher allergy prevalence than early introduction of allergenic foods; (charts from that study are several paragraphs below here);

b) sibling studies; for examples three such studies, that either found adverse effects of breastfeeding or found the claimed benefits of breastfeeding to be essentially non-existent, go to Section 1.f.;

c) either a large effect or a dose-response gradient, in any kind of study. (Importance of these factors is indicated in the American Medical Association’s Manual for Evidence-based Clinical Practice (2^nd Edition), p.375⁽²⁾   Along those lines, note  the following:

 in Section 2.e:

--  large effects of autism prevalence in association with breastfeeding, as found in three separate studies:  The smallest effect was a 25% increase (from breastfeeding at departure from the hospital versus no breastfeeding), with 130% and 175% increases with breastfeeding at four weeks and at six months;

--  a dose-response gradient formed by those three studies, going from the smallest effect with the least exposure to the largest effect in association with the greatest exposure;

--  a dose-response effect of autism in relation to duration of breastfeeding found within the Shamberger study. (see Section 2.a)

-- Also:  A dose-response neurological effect was found in the Vreugdenhil et al. study in Section 2.d.1, in which formula-fed children performed better than their breastfed counterparts on a test of executive function, and in addition the children who were breastfed for longer periods performed worse than those breastfed for shorter periods.

-- See many other studies providing evidence of dose-response relationships between breastfeeding and adverse outcomes in Section 2.a.

Large study size is also recognized as important in assessing quality of evidence from studies. 

-- On a web page of the Norwegian University of Science and Technology (dated 6/2010), researchers from the University are quoted as referring to “the largest study that has been done on breastfeeding and health” (studying more than 17,000 women and children, in Belarus) and stating, “This study cuts the legs out from underneath most of the assertions that breastfeeding has health benefits.”^2b

-- Subsequently, a (2011) study of 127,000 children in Canada found a 25% increase in autism associated with breastfeeding on departure from the hospital.^2a

-- The Shamberger study found a direct correlation between autism prevalence and breastfeeding duration based on data from all 50 U.S. states and 51 U.S. counties. (see Section 2.a)

Relevance to long-term health:  The vast majority of studies of health effects of breastfeeding assess outcomes only at very early ages, which can provide a distorted picture of the long-term impact of developmental toxins.  One of the developmental toxins that is high in human milk and also closely associated with autism prevalence, mercury, is known to have latency of effect that can be of many years’ duration.^2e   Most children who will be diagnosed with autism will not be identified until age 5 or later,^2c and a large percentage are not identified until after age 8;^2a the average age of diagnosis of ADHD has been found to be age 7.^2d  Not surprisingly, the several studies that have found strong associations of autism with breastfeeding, in dose-response gradients (see above and Section 2.e), did not limit their assessments to very young children.  The children in the very large Belarus study that was mostly negative about breastfeeding, referred to above, were followed until age 6.  For more on failure of studies to assess long-term effects, and on the far more adverse effects of breastfeeding found in studies that did follow breastfed children into later years, see Section 1.d.

A 2016 study (see charts below) has three of the above-described features, making it especially suitable for guidance on the question of breastfeeding: 

(a) it was a randomized study, the gold standard of study types,

(b) the differences in observed outcomes were very substantial, and

(c) dose-response effects were found.

Also, although age 3 is still relatively young for best demonstration of long-term effects, it is nevertheless better than the ages at which outcomes are observed in many or most studies of effects of breastfeeding.

Below:  Prevalences of various allergies, with and without exclusive breastfeeding

This study can probably be found online at xhttp://www.nejm.org/doi/full/10.1056/NEJMoa1514210?query=TOC

………………………………..

This article will not list the studies that have found favorable effects of breastfeeding, since those are very adequately presented elsewhere.  A good place to read a presentation of studies finding benefits of breastfeeding is in the Surgeon General's document mentioned above.⁽¹⁾  Be sure to notice (on p. 33) her inconspicuous acknowledgement that studies such as these are of the type (observational) that can only provide "inferences" about effects of breastfeeding, as opposed to "scientifically sound" studies that she hopes will be carried out on this subject in the future.  For a more complete discussion of the weaknesses of the studies that are thought to provide evidence about benefits of breastfeeding, including about the known confounders of higher socio-economic status and less household smoking among women who are likely to breastfeed (both of which are known to result in better health outcomes in children), go to www.breastfeeding-benefits.net. 

Contents of this article:

Section 1:  Biases in studies, and what often goes wrong

Section 1.a:  Links to summaries about toxins in breast milk and their effects

Section 1.b:  Biases among the general public, carrying over to studies

Section 1.c:  Studies frequently going wrong, and reasons for that, according to an eminent doctor-scientist:

“False conclusions are normal, and many established medical recommendations have been found to be ineffective or harmful.”  “Claimed research findings may often be simply accurate measures of the prevailing bias.”

-- Publication bias

-- Emotion/ bias

Section 1.d:  Frequent failure to look at long term effects:

-- Studies completed too soon to see full effects of exposures, or without testing capable of detecting ADHD or ASD

-- Why breastfeeding can seem to show positive results at first, turning to negative later

-- Delayed neurotoxicity that may be manifested many years later

Section 1.e:  Important health information to consider other than the typical studies

Section 1.f:  Sibling studies, which avoid the effects of confounders that are likely to give false impressions of benefits of breastfeeding, and which found excellent evidence that those claimed benefits generally do not exist.

Section 2: Many studies that have found associations between breastfeeding and adverse health effects:

Section 2.a:  Studies finding disease incidences to increase in proportion to increases in breastfeeding

Section 2.b:  General studies finding associations between breastfeeding and adverse health effects

Section 2.b.1:  ADHD, learning disabilities, and effects of PBDEs

Section 2.b.2:  Obesity

Section 2.c:  Other studies that have found apparent adverse effects of breastfeeding

Section 2.c.1:  Diabetes-related studies: 

Section 2.c.2:  Studies related to asthma and/or allergies  

Section 2.d

Section 2.d.1:  Or filter your current search General neurological development;

Section 2.d.2:  immune dysfunction; motor skills

Section 2.e:  Autism

Section 2.f:  Cancer risk

Section 2.g:  Recurrent ear infections 

Section 2.h:  SIDS-related studies

Section 2.i:  Studies indicating predominantly postnatal, not prenatal, vulnerability to toxins that are especially heavily present in breast milk

Section 2.j: Studies indicating high levels of important developmental toxins in breastfed as opposed to bottle-fed infants

Section 2.k:  Reduction of testosterone, with serious implications for cognitive development and for the viability of modern societies

Section 2.l:  General health effects

Section 3: Long-term detrimental effects

Section 4: Studies indicating hazardous exposures to developmentally-toxic dioxins

Section 1 

1.a:  Links to summaries about toxins in breast milk and their effects:

There is a great deal of undisputed evidence showing that typical human milk in contemporary developed countries is high in developmental toxins.  Among those are dioxins in doses found (in EPA research) to be scores to hundreds of times higher than the EPA-determined safe level, and in concentrations scores to hundreds of times higher than in formula.  The situation is similar with regard to mercury and PBDEs.  For a quick summary of the most significant points on this matter, see the introductory paragraphs of www.autism-origins.info.  For extensive details, see www.breastfeeding-toxins.info.  In addition, there is considerable evidence showing breastfeeding to be closely correlated with increased rates of autism and childhood cancer. (See www.pollutionaction.org/breastfeeding-and-autism-and-cancer.htm)  There is also considerable historical evidence (mostly provided by the CDC) about other disorders that are alleged to be reduced by breastfeeding, showing that they actually increased substantially along with breastfeeding, typically tracking precisely with the increases in breastfeeding.  Close correlations of increases in breastfeeding with increases in childhood diabetes, along with examination of scientific evidence linking the two, can be found at www.breastfeeding-and-diabetes.info.  Similar correlations and scientific evidence regarding asthma and allergies can be found at www.breastfeeding-and-asthma.info.   Close correlations between increases in breastfeeding and increases in ADHD and serious psychological problems are dealt with at www.breastfeeding-health-effects.info.  Historical data showing especially close tracking between increases in childhood obesity and earlier increases in breastfeeding can be found at www.breastfeeding-and-obesity.info. 

Clearly there are also many studies that have found associations of breastfeeding with various benefits, just as there are at least 60 studies that have found adverse effects of breastfeeding, plus a clear majority of high-quality studies on breastfeeding and SIDS that found no benefit of breastfeeding.(see “Many studies” below).   Most of the studies finding adverse effects of breastfeeding (like the studies finding benefits of breastfeeding) are of the observational type; but at least six of them are either randomized, controlled trials (two in Belarus), a sibling study, or large-scale epidemiological studies (three), avoiding the weaknesses of the typical, local observational studies.  Also, the research that has found high levels of developmental toxins in human milk (as reported by government agencies such as the CDC, NIH, EPA, and ATSDR) has generally not consisted of observational studies.

Of particular interest are the many studies that have found adverse health effects to increase as the amount of breastfeeding increased.  This provides particularly strong evidence that the adverse effects are direct results of the breastfeeding.  Those will be listed first.

Section 1.b:  Biases among the general public, carrying over to studies:

A special reason for the fact that many studies have found benefits of breastfeeding is the emotional devotion to the cause of breastfeeding that is widespread in the general population (see upcoming paragraphs); researchers are very much subject to those same biases.  It is standard in published studies that the authors are expected to indicate special interests that the authors might have that could be related to the subject under consideration, especially financial interests; and the reason for that is obvious.  It's the same reason why judges are expected to recuse themselves in cases in which they have a personal interest.  It is completely normal that people's personal biases affect what they see, including what they look for, what they record or don’t record, and how they interpret what they see.  The author of this article personally knows only one person who is an author of a journal-published study that deals with breastfeeding and its health effects.  That person, an M.D., breastfed one of her children for 4½ years, which is evidence of true devotion to breastfeeding.⁽³⁾  When reading her study, one sees no acknowledgement that the author might have a personal bias on the subject.  Only if one reads her study with a careful eye can one see evidence of result-altering effects of that bias.  The author followed a very unusual (if not unique) policy of classifying cases of a specific disorder as "congenital" even if those cases were not first observed until almost two years after birth.  That divergence from standard classification procedures for that disorder, in this study, resulted in many cases' being placed into the category that was the opposite of the category into which they would normally have been placed.  That unorthodox treatment of the data in turn resulted in a finding that was favorable to effects of breastfeeding, whereas following normal classification procedures would have resulted in a finding unfavorable to breastfeeding.⁽³⁾   So it is entirely likely that the findings of this study (and of many or most studies of effects of breastfeeding?) were essentially determined by the lead author’s personal bias in favor of breastfeeding; but such biases are never acknowledged. 

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Section 1.c:  Studies frequently going wrong, and reasons for that:

It would not be surprising if most studies that have found favorable effects of breastfeeding did so essentially because of

    a) unacknowledged biases on the part of the researchers, such as in the case just mentioned; (also see “Emotion/bias” below), or

    b) confounders that are known to apply in such studies, with bottle-feeding households being disproportionately of low income and with smokers present, leading to adverse health effects (see www.breastfeeding-benefits.net and also ^3-0), or

    c) assessments of child health outcomes in children carried out at a stage too soon to see the full effects of early exposures (see “Studies completed too soon,” just below), or

    d) such studies typically reaching false conclusions, which is as would be expected according to a statement of the U.S. Agency for Healthcare Research and Quality regarding observational studies;⁽²⁾  the Surgeon General acknowledges that all of the studies finding benefits of breastfeeding fall into that category.(p. 33 of 1)  Also see “False conclusions” below.  

    e) The clearly-stated positions of the parties that provide funding for research.  One can see obvious indications of strong bias of that kind by going to the website of the U.S. Department of Health and Human Services that deals with breastfeeding (www.womenshealth.gov) and following the link for breastfeeding information, to see expression of the unequivocal position of the U.S. government regarding breastfeeding, and by implication the kind of conclusions that are expected from studies that it funds.  Amid the many claims of benefits of breastfeeding, there is no mention of any of its negative characteristics (except in the cases of specific medical problems), even though there are many such drawbacks (see later).

False conclusions are normal, and many established medical recommendations have been found to be ineffective or harmful: 

Many observational studies in the last two decades resulted in recommendations of Vioxx, of hormone replacement therapy for post-menopausal women, and of various vitamin supplements; but later experience and/or large, randomized studies showed those recommendations to lead either to harm or at best to no effect.^(3a2) A 2013 study by twelve MD’s, published in Mayo Clinic Proceedings, arrived at relevant findings in their investigation of 363 articles in a major medical journal; that study’s findings were extremely similar to those in a 2012 article by another team of MD’s writing in the Journal of the American Medical Association,^(3a3) concerning research into established medical practices, as follows:  The lead author stated, "A large proportion of current medical practice, 40%, was found to offer no benefits in our survey of 10 years of the New England Journal of Medicine. These 146 practices are medical reversals. They weren't just practices that once worked, and have now been improved upon; rather, they never worked. They were instituted in error, never helped patients….”^(3a4)

There are also relevant statements by Dr. John Ioannidis, who is chair in Disease Prevention at Stanford University School of Medicine and also adjunct professor at Harvard School of Public Health: “Claimed research findings may often be simply accurate measures of the prevailing bias.”

 And also,     “…in modern research, false findings may be the majority or even the vast majority of published research claims,” resulting from (among other things) “various combinations of selective or distorted reporting of the results;… manipulation of the outcomes and analyses reported is a common problem.”^(3a5)  (Note that the above statements were made by a highly-placed doctor and scientist, not by a critic from outside the profession.)  Arriving at certain desired results, and thereby getting studies published, is a recognized way for people to gain advancement in their fields.  That is in addition to the effects of personal biases of the kind (mentioned earlier) that causes somebody to breastfeed a child for 4 1/2 years, later publishing a study that inconspicuously treats data in a very unorthodox way and thereby leads to a finding favorable to breastfeeding.

Unjustifiable recommendations of procedures and practices can often result in harm to the patient.  There is probably no better example of this than the case of breastfeeding, with doctors advising mothers to feed infants a substance that is known to often be hundreds of times higher in developmental toxins than an alternative that very satisfactorily fed the mid-century U.S. generation; this recommendation continues while several unexplained epidemics (diabetes, asthma, obesity and allergies, plus large increases in ADHD and autism) are going on among children and continuing into their adult years, epidemics that arose only after breastfeeding increased greatly; and those epidemics have often varied up and down in close correlation with high and low variations in rates of breastfeeding.  One can read more about this at www.breastfeeding-health-effects.info and www.breastfeeding-and-diabetes.info

Publication bias:  This is another recognized problem in these studies:  a strong tendency for positive results to be far more likely to be published than negative results, or more likely to be published than results supporting the "null hypothesis."  This stems partly from the publishers' inclination to publish mainly studies with findings that are deemed newsworthy and likely to attract paying customers, or that support the biases of the publishers; and it also results partly from the lower likelihood that the authors of studies will try to publish results of a study that merely finds no positive effect of a treatment under consideration.⁴  This is especially likely to be the case given the fact that the authors or their funders often have to bear substantial costs of having studies like these published.  Related to the above is research bias, which takes many forms, at tabulated by the AHRQ.^4b

Emotion/bias:  To get some idea of how much emotion there is involved in the matter of breastfeeding (and therefore how heavily researchers might be influenced by the prevalent emotions), one can look at any online blog in which the importance of breastfeeding is questioned, such as the one at www.sciencebasedmedicine.org/are-the-benefits-of-breastfeeding-oversold.  One comment there refers to the “relentless, absolutely relentless guilt-tripping of women who choose to not breastfeed ...."  (Following serious difficulties with breastfeeding, a mother made) "the rather obvious decision to move to formula.  Oh.My God…. The unrelenting bullshit we got from the La Leche crowd and their fans. “You can’t bond with your child if you don’t breast feed!” “You’re depriving your child!” on and on, and those were the most mild examples. It got far worse."  Another comment referred to "attacks ... on one of my best friends in the mall for feeding her infant formula...."  Another referred to "these breastfeeding advocates who tell moms they are selfish, or poisoning their babies, or any of the other God-awful things I’ve heard the last 5 months."

Rational consideration of evidence for or against breastfeeding is something that simply cannot be assumed, including on the part of the people doing studies on the subject.  However, it isn't hopeless; see "Many studies..." below.

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Comments or questions are invited.  At the next link are comments and questions from readers, including six doctors.  Some of the doctors have been critical but others have been in agreement with us (including one with children and one who says she has delivered thousands of babies); they put into briefer, everyday language and personal terms some important points that tend to be immersed in detail when presented in our own publications.  Also, we have responded to many readers’ questions and comments, including about having breast milk tested for toxins and about means of trying to achieve milk that is relatively free of toxins, including the “pump and dump” option.  To read the above, go to www.pollutionaction.org/comments.htm .

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Section 1.d:  Frequent failure to look at long term effects: Studies completed too soon to see latent or slowly-developing effects of exposures, or without testing capable of detecting ADHD or ASD:

Mercury is well known to be a serious neurodevelopmental toxin.  (It comes up in this discussion because it is high in breast milk and low in infant formula -- see www.breastfeeding-toxins.info, Section 1.c)  However, its adverse effects apparently often don’t become obvious in children until after a certain age; there are even likely to be indications of favorable effects of mercury (and of the breastfeeding that delivers it) at early ages, such as at 12 months of age in a Faroe Islands study (Grandjean et al., 1995).^(3a)   In other studies, at 5½ years of age, associations with mercury exposure were found to be favorable to the childrens’ development in several tests, although unfavorable in others.  There may be a transition in effects of breastfeeding (and the toxins it delivers) starting to take place at about that age.   Assessments that were found in testing after age 6 finally found clearly negative associations with mercury exposure;^(3b)(3a0) before that age, outcomes that often seemed favorable were apparently only transitory.  According to the EPA in its summary of investigations about the Minimata mercury poisonings in Japan, “in the case of maternal exposure, symptoms usually did not appear until 5 to 8 years after birth of the child.”^(3b0)  In addition, a very high percentage of children with ASD (as well as ADHD) are of normal or high intelligence, so their impairments (even though substantial) may very well not show up on standard tests of cognitive abilities.  One might question whether testing of children at early ages or testing by means of standard tests of cognitive abilities should be considered to be meaningful in determining effects of developmental toxins. 

Why breastfeeding can seem to show positive results at early ages (when studies are likely to be conducted), turning to negative later:

   a) Immune cells are known to be contained in breast milk.  Obviously those immune cells, while they are still alive, are helpful in warding off early childhood infections.  But those extermally-provided cells eventually die; and while they are still active they are shielding the infant from microbial challenges that are apparently needed to stimulate development of the child’s immune system.  As in the case of vaccinations, long-term immunity is created by subjecting a child’s system to challenges, not by protecting the child from microbes. Quoting from the UCLA Food and Drug Allergy Care Center, "Overwhelming evidence from various studies suggests that the hygiene hypothesis explains most of the allergy epidemic."^(3d)  Immune cells in breast milk have a hygienic, anti-microbial effect at a time when that effect apparently actually harms development of the immune system.  Typical studies reach their conclusions before the longer-term effects of impaired development become significant.

   b)  There is no doubt that breast milk has nutrients that are beneficial, even aside from the kind noted above that are only initially helpful.  The only problem is that it also contains high levels of toxins, far higher than in formula or other alternative foods and far higher than established standards of safety.  Studies might observe the beneficial effects at a time when the harmful effects of the toxins are still latent.  Carcinogens, which include the dioxins that are typically present in contemporary human milk in concentrations scores to hundreds of times higher than the EPA-determined safe dose (see www.breastfeeding-toxins.info), often have latency periods of decades.  According to the neurology expert, Bernard Weiss, “manifestations of damage emerge only after compensatory processes have been exhausted…. Latency periods as long as 15 years have been reported after the Minamata outbreak (resulting from methylmercury exposure)…. Most observers agree that the appearance of clinical signs is merely the ultimate phase of a neurodegenerative process whose inception might even be traced to events occurring during early development….  Over time, the aging process will further reduce the number of cells until those that remain are too few to sustain function, and overt effects then erupt.”^(3d1)

Effects of toxic exposures may simply take so long to become visible that they are merely overlooked in typical studies that assess children at early ages.  A German study found effects of PCBs in human milk to be negative but insignificant when assessed at early ages but significantly adverse at later ages, and "negative associations with PCB increased with age."(3c)  In a Canadian study of “delayed neurotoxicity produced by methylmercury,” evidence was provided from studies of long-term effects of developmental exposure to methyl mercury (two studies with monkeys as well as a study of over 1100 accidentally-exposed human patients); neurological abnormalities were observed in midlife, including abnormalities that were not present previously in the monkeys; in the humans, there was difficulty in performing daily activities that increased with age, compared with similar other people, providing “good evidence for delayed neurotoxicity that may be manifested many years after cessation of exposure.”(3e)

EPA scientists go into detail on the subject of “long-latency delayed neurotoxicity,” referring especially to long-latency effects of methylmercury and of triethyltin (a component of some pesticides and plastics); they also referred to “increasingly compelling evidence for an association between aggressive behavior during childhood and later increased criminality in males, but not females, as a result of developmental exposure to neurotoxicants;”  exposure to maternal tobacco smoke was also “associated with increased criminality during adulthood as a result of developmental exposure.”(3f)  With regard to developmental exposure to tobacco smoke, note in Section 2.f that "breast-fed infants of smoking mothers have urine cotinine levels (a marker for smoke exposure) 10-fold higher than bottle-fed infants whose mothers smoke."  There is clearly a wide array of undesirable long-term effects of infant exposure to toxins, often observed only in adulthood and middle age; these are effects that would be unlikely to show up in the studies that find no obvious harmful effects when assessing children who were exposed as infants to high levels of development toxins such as mercury and PCBs.

For many other examples of health outcomes of exposure to breastfeeding that have been found (in published scientific studies) to become worse with age, see Section 3.a.1 of www.breastfeeding-and-asthma.info as well as section (a) of “Obesity” later in this article.

Also see “Section 3: Long-term detrimental effects” later in this article.

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Section 1.e:  Important health information to consider other than the typical studies:

Considering the very questionable nature of most of the studies on the subject of breastfeeding and its health effects, a logical question to ask is, "What else can we consider when trying to determine whether or not a mother should breastfeed her infant."  One thing to think about is the undisputed high levels of developmental toxins that have been found in breast milk, in doses scores to hundreds of times higher than in infant formula, and often in doses many times higher than the EPA-determined safe level, as described by documents from the EPA and other authoritative sources; for details, see www.breastfeeding-toxins.info.  Also, by now there is a great deal of historical health data (mainly from the CDC) regarding incidences of specific childhood diseases, covering the period since breastfeeding started to increase in the 1970's.  One can look at the historical data for each of the disorders that are alleged to be reduced by breastfeeding, and see what actually happened after breastfeeding greatly increased beginning in 1971.  There are not only major increases in almost all of those disorders along with increases in breastfeeding, but also variations in incidences of those diseases (very sharp increases, very mild increases, plateaus, and even one major decline), variations that have correlated closely with similar variations in breastfeeding rates.  For details, go to www.breastfeedingprosandcons.info . 

For some examples of the many different disorders that could be linked to the known toxins in breast milk but which are not tested for in most studies, go to Section 5.f of www.autism-research.net/postnatal-effects.htm.

Section 1.f:  Sibling and epidemiological studies, which minimize the effects of the confounders that give the impression of benefits of breastfeeding, and which have found good evidence that those claimed benefits generally do not exist:

    A 2005 American study (Evenhouse et al.), drawing on data from the U.S. National Longitudinal Study of Adolescent Health for 2,734 sibling pairs, examined the relationship between breastfeeding history and 15 indicators of physical, emotional and cognitive health, including diabetes, asthma and allergies.  The authors concluded that “Nearly all of the correlations found in the between-family model (as in typical observational studies) become statistically insignificant in the within-family (sibling) model.”  The only area (out of 15) in which breastfed infants were found to do better, with statistical significance, was in the Peabody Picture Vocabulary Test; on that test, six months of breastfeeding was associated with a one percentile improvement on that test (0.16 percentiles per month of breastfeeding).  In one of the two forms of their sibling model, they found that the breastfed infant was more likely to become overweight than a non-breastfed infant.(3g)

The authors of the Evenhouse study considered the improvement on the vocabulary test to be an important indication of beneficial effect of breastfeeding.  It is indeed noteworthy that this apparent effect appeared to actually constitute high-quality evidence of a benefit of breastfeeding.  But, especially considering that all fourteen other tests of possible benefits of breastfeeding did not reveal beneficial effects in this sibling test, one should think about whether that one percentile improvement in vocabulary is really very significant; it should be seen in the context of other evidence, such as the study by a highly-published scientist, examining data from all 50 U.S. states and 51 U.S. counties, finding that there was a direct, positive correlation between exclusive breastfeeding and autism; and also that the correlation with autism became stronger as duration of exclusive breastfeeding became longer.(3h)  Note that this was an epidemiological study, and, according to the EPA, “Epidemiologic studies of exposed human populations provide the most convincing evidence of human health effects.”(3k)  Also note that two other studies, in the U.S. and U.K., provided compatible evidence of links between breastfeeding and autism. (see Section 2.e)

Another sibling study that applies to alleged benefits of breastfeeding is the 2014 Colen et al. study, which found that asthma was “one outcome for which breastfeeding duration is consistently associated with poorer childhood health and wellbeing across all three models.”  In addition, outcomes of breastfeeding were negative for body mass index, obesity, and intelligence.  The authors considered this data to suggest that “for some outcomes, breastfed children may actually be worse off than children who were not breastfed.”  Of 11 outcomes examined in this sibling study, none showed statistically significant benefits of breastfeeding.  Continuing to quote from the study, “The findings presented here are consistent with those from a small but growing literature that seeks to more accurately assess the association between breastfeeding and child health and well-being.”^(3m)

Also see the Michels et al. sibling study in Section 2.b.2, part (d).

Section 2:  Many studies have found associations between breastfeeding and adverse health effects:

Note:  Below are just some studies that were relatively easily found.  There are no doubt many other studies negative to breastfeeding, if one were to take time to look for them.

Section 2.a:  Studies finding adverse outcomes to increase in proportion to increases in breastfeeding:

If a study finds that incidence of a disease increases in proportion to the amount of breastfeeding (in a dose-response relationship), that provides especially strong evidence that the outcomes result specifically from lactational exposure to toxins. 

        Wright AL et al., Maternal asthma status alters relation of infant feeding to asthma in childhood.   Adv Exp Med Biol. 2000;478:131-7.  Found at  http://www.ncbi.nlm.nih.gov/pubmed/11065066  "For children with maternal asthma, the percent developing active MD asthma increased significantly with longer duration of exclusive breastfeeding."

        Philippe Grandjean et al., Allergy and Sensitization during Childhood Associated with Prenatal and Lactational Exposure to Marine Pollutants    Environ Health Perspect. 2010 October; 118(10): 1429–1433. PMCID: PMC2957924  found at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2957924  This study of children in the Faroe Islands, published in 2010, found that risk of allergy development increased with each additional month of breastfeeding.

       Hong X, J et al., Gene polymorphisms, breast-feeding, and development of food sensitization in early childhood.    Allergy Clin Immunol. 2011 Aug;128(2):374-81.e2. doi: 10.1016/j.jaci.2011.05.007. Found at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3149737/  In this 2011 U.S. study of 739 children up to age 6, increases in allergies found to be associated with breastfeeding were quite large and were greater for children who were breastfed for longer durations.

 Chuang CH et al., Infant feeding practices and physician diagnosed atopic dermatitis: a prospective cohort study in Taiwan.   Pediatr Allergy Immunol. 2011 Feb;22(1 Pt 1):43-9. doi: 10.1111/j.1399-3038.2010.01007.x.   Found http://www.ncbi.nlm.nih.gov/pubmed/20573037   In this 2011 Taiwan study of 18,733 babies, it was found that, "After adjustment for potential confounders, the overall results showed that the increased duration of breastfeeding seemed to increase the risk of AD (atopic dermatitis) at 18 months in children.

       Purvis DJ, et al., Risk factors for atopic dermatitis in New Zealand children at 3.5 years of age.  Br J Dermatol. 2005 Apr;152(4):742-9.  http://www.ncbi.nlm.nih.gov/pubmed/15840107       In this 2005 New Zealand study of 550 children at 3½ years of age, it was found that the odds ratios of developing atopic dermatitis increased  from 1 to 6.1 to 9.7 as the children’s feeding histories went from (a) never breastfed, to (b) less than 6 months of breastfeeding, to (c) more than 6 months of breastfeeding. 

Jessica Paton, et al., Infant Feeding Practices and Nut Allergy over Time in Australian School Entrant Children,   Int J Pediatr. 2012; 2012: 675724.  Published online 2012 July 3. doi: 10.1155/2012/675724   PMCID: PMC3397206   found at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3397206  In this 2012 Australian study of peanut allergy in 15,142 school children, it was found that the odds ratios of developing the allergy progressively increased from 0.63 to 0.83 to 1.43 as the categories of the childrens’ infant feeding went from (a) those fed only foods other than breast milk before six months, to (b) those who were partially breastfeed, to (c) those who were exclusively breast fed.  The authors also noted that other research concurred with theirs, in finding that the odds of developing peanut allergy were almost three times higher when comparing children who had had prolonged breastfeeding with children weaned at or before 6 months.

      Bergmann RL  et al., Breastfeeding duration is a risk factor for atopic eczema.  Clin Exp Allergy. 2002 Feb;32(2):205-9.  Found at http://www.ncbi.nlm.nih.gov/pubmed/11929483  In this German study of 1314 infants born in 1990, analyzing the effect of any breastfeeding duration on the prevalence of atopic eczema, it was found that the prevalence of atopic eczema in the first seven years increased with each additional month of breastfeeding.

       Shamberger RJ., Autism rates associated with nutrition and the WIC program.   King James Medical Laboratory, Cleveland, Ohio  J Am Coll Nutr. 2011 Oct;30(5):34853   At  http://www.ncbi.nlm.nih.gov/pubmed/22081621  This U.S. study of all 50 U.S. states and 51 U.S. counties, carried out by a highly-published nutritionist and Fellow of the American College of Nutrition, found that "exclusive breast-feeding shows a direct epidemiological relationship to autism" and also, "the longer the duration of exclusive breast-feeding, the greater the correlation with autism."

Gascon et al.,  Polybrominated Diphenyl Ethers (PBDEs) in Breast Milk and Neuropsychological Development in Infants   US National Library of Medicine, NIH,  Environ Health Perspect. 2012 December; 120(12): 1760–1765  PMC3548276.  at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548276   This 2012 study reported that its "findings suggest an association between PBDE concentrations in colostrum (early breast milk) and impaired infant cognitive development."  The authors also pointed out that “in the group of children breastfed for a longer period the association between BDE-209 exposure and neuro-development impairment was somewhat stronger….”

       Alaluusua et al., Developmental dental defects associated with long breast feeding, European Journal of Oral Sciences, 1996, DOI: 10.1111/j.1600-0722.1996.tb00131.x at http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0722.1996.tb00131.x/abstractA 1996   This  European study investigated mineralization defects in the permanent teeth of children, in two separate study groups.  The authors found that mineralization defects were substantially associated with the duration of breastfeeding in both groups.  They attributed this to presence of dioxins in the breast milk.

Also see the Colen study in Section 1.f, concerning the consistent link between asthma and breastfeeding duration.

Also see the Ettinger et al. and Lozoff et al. studies in Section 2.j, concerning increasing infant lead levels with increasing duration of breastfeeding.

Also see the Grandjean et al. study in Section 2.l, about greater reduction of growth with each additional month of breastfeeding, up to 6 months.

Also see the Al-Saleh study in Section 2.d about oxidative stress in infants increasing in a dose-effect relationship with increased mercury in breast milk.

Section 2.b: General studies finding associations between breastfeeding and adverse health effects:

Section 2.b.1:  ADHD

Hoffman, et al., Lactational Exposure to Polybrominated Diphenyl Ethers and Its Relation to Social and Emotional Development among Toddlers  Environ Health Perspect. 10/2012;  seeing text above Figure 2 in www.ncbi.nlm.nih.gov/pmc/articles/PMC3491946/.  This study, of effects of PBDEs in breast milk, found that children who had consumed breast milk with first and second quartile levels of the predominant form of PBDEs showed over three and two times the likelihood of later having ADHD, based on behavior test scores, compared with children who had consumed breast milk with below-median levels of PBDEs.

Gascon M. et al., Effects of pre and postnatal exposure to low levels of polybromodiphenyl ethers on neurodevelopment and thyroid hormone levels at 4 years of age. Environ Int. 2011 Apr;37(3):605-11. doi: 10.1016/j.envint.2010.12.005. Epub 2011 Jan 14  found at www.ncbi.nlm.nih.gov/pubmed/21237513   This study found that gestational exposure to PBDEs in the mothers in a study had no significant adverse effect, but exposure to those same mothers' PBDE levels via breastfeeding did have a substantial effect, including an 80% increase in relative risk of attention-deficit problems and a 160% increased relative risk of poor social competence.^(81b1)

Children in a 2015 study were breastfed for a median of less than one month, but even that minor exposure to increases in PCBs transferred by breastfeeding was associated with significantly higher scores at age 8 in teachers’ rating scales for ADHD-related behavior.  For more explanation of this study, see Section 2.b of www.breastfeeding-and-adhd.info.  (Verner et al., Measured Prenatal and Estimated Postnatal Levels of Polychlorinated Biphenyls (PCBs) and ADHD-Related Behaviors in 8-Year-Old Children, Environ Health Perspect; DOI:10.1289/ehp.1408084 , Vol. 123, Issue 9, Sept. 2015, at http://ehp.niehs.nih.gov/1408084)

    For additional evidence of causal effect of PBDEs on ADHD-like behavior:  Eskenazi B et al., In utero and childhood polybrominated diphenyl ether (PBDE) exposures and neurodevelopment in the CHAMACOS study    Environ Health Perspect. 2013 Feb;121(2):257-62. doi: 10.1289/ehp.1205597. Epub 2012 Nov 7  at http://ehp.niehs.nih.gov/1205597  Note that PBDEs are high in breast milk --see Section 1.b of www.breastfeeding-toxins.info

--  In the above study (Table 1) effects of postnatal PBDE exposures on ADHD-like behavior as judged by teachers were found to be twice as high as effects of prenatal exposures to PBDEs.

    Given the above links between PBDEs and ADHD-like behavior, it is of relevance that breast-fed infants have been estimated to be exposed to 306 ng/kg body weight/day PDBE compared with 1 ng/kg body weight/day in adults, as found in the following:  Costa et al., Polybrominated diphenyl ether (PBDE) flame retardants: environmental contamination, human body burden and potential adverse health effects. Acta Biomed. 2008;79(3):172–183.

    S Patandin et al.,  Effects Of Environmental Exposure To  Polychlorinated Biphenyls And Dioxins On  Growth And Development In Young Children:  A Prospective Follow-Up Study of Breast-Fed and Formula-Fed Infants from Birth Until 42 Months of Age  at   http://Repub.Eur.Nl/Res/Pub/19721   Table 7.5 and accompanying text.  This Dutch study found a strong association of exposure to PCBs specifically via breastfeeding with problems with inattention and hyperactivity in infants at 42 months after birth. The study distinguished between effects of prenatal and lactational exposure, and found that only the lactational exposure was associated with “less sustained attention” and slower reaction time.

     Polańska et al., Exposure to Environmental and Lifestyle Factors and Attention-Deficit / Hyperactivity Disorder in Children – A Review of Epidemiological Studies,   International Journal of Occupational Medicine and Environmental Health 2012;25(4):330 – 355 DOI 10.2478/S13382-012-0048-0   at http://repropl.com/attachment/exposure_to_environmental_and_lifestyle_factors.pdf

According to this study, “nicotine is transmitted through breast milk,” and “generally it appears that the children of smokers are approximately 1.5–3 times more likely to have ADHD or ADHD symptoms than the children of non-smokers.” This should be seen in combination with the finding (in section 2.f  below) that "breast-fed infants of smoking mothers have urine cotinine levels 10-fold higher than bottle-fed infants whose mothers smoke." (Cotinine is a marker for smoke exposure)  It should be safe to say that the children of smokers who receive the greatest effects of the smoking exposure are likely to be those who have the 10-times-higher cotinine evidence of smoking exposure (i.e., the breastfed ones).

     Day et al., Effects of prenatal tobacco exposure on preschoolers’ behavior. J Dev Behav Pediatr 2000;21(3):180–8.   This study indicated that postnatal (not prenatal) exposure predicted attention problems in 3-year-old children. As noted in the previous paragraph, children with by far the greatest postnatal exposure to effects of maternal smoking are breastfed children.

Lind et al., Breastfeeding and Later Psychosocial Development of Children at 6 Years of Age, Pediatrics Vol. 134 No. Supplement 1 September 1, 2014, pp. S36 -S41 (doi: 10.1542/peds.2014-0646G)    at http://pediatrics.aappublications.org/content/134/Supplement_1/S36.full,  citing Breastfeeding and subsequent social adjustment in six- to eight-year-old children. J Child Psychol Psychiatry. 1987;28(3):379–386pmid:3597562.  Referring to the earlier study, the Lind et al. 2014 study reports that teacher ratings revealed a “significant association between increasing breastfeeding duration and conduct disorder ratings at 7 years.”^(25a4)

     Cheuk et al., Attention-Deficit Hyperactivity Disorder and Blood Mercury Level:  a Case-Control Study in Chinese Children  Neuropediatrics 2006; 37: 234–240  at http://www.uni-kiel.de/medinfo/material/seminar_ws0809/Artikel%20Statistische%20Modelle%20WS%202008_09.pdf. Children with blood mercury levels above a certain level (elevated due to fish consumption, but still less than one-sixth of the level considered to be poisoning) were found in this study to have a 9.7 times higher risk of having ADHD, after adjustment for confounding variables.  Knowing that, be aware that infants who are breastfed have been found to have two and three times the mercury levels after six months or a year of breastfeeding, compared with infants who have been bottle fed, and also that typical human milk contains four times the level of mercury that is allowed in U.S. bottled water, and often higher.(8)

--   Lee et al., Association of serum concentrations of persistent organic pollutants with the prevalence of learning disability and attention deficit disorder,  J Epidemiol Community Health 2007;61:591–596. doi: 10.1136/jech.2006.054700 at http://jech.bmj.com/content/61/7/591.full.pdf+html.   This was apparently the only study that has been carried out on the association between background exposure to POPs and clinically significant developmental disorders, such as learning disability or attention deficit disorder, among children from a general population.   It utilized data for 278 children aged 12–15 who were included in the U.S. National Health and Nutrition Examination Survey 1999–2000.  The authors found dramatically increased odds of the children’s having these disorders if they had detectable levels of dioxins or furans. (Furans are chemical relatives of dioxins that are usually grouped together with dioxins.)   The average odds ratio of having Learning Disability for those with detectable levels of dioxins/furans, compared with those without detectable levels, was 2.33 (that is, a 133% increased likelihood); and the average odds ratio of having Attention Deficit Disorder for those with detectable levels of dioxins/furans, compared with those without detectable levels, was 3.02 (three times as likely).  This study should be seen in combination with findings by a two-researcher team headed by an EPA senior scientist (citing five other studies with compatible findings) indicating that six or more months of breast-feeding would result in accumulated dioxin exposure 6 times higher than that of a formula-fed infant during the first year of life; accumulated exposure was expected to still be twice as high among the breastfed children after 10 years.(8a)  In a 2011 study, by 13 scientists, it was determined that, after the infants studied had grown to ages18 to 26, average dioxin concentrations were still twice as high in the breastfed young men as in those who had been formula fed.(8b)  It should be safe to assume from this that by far the principal determinant of the extent of a developing child’s dioxin exposure and accumulation is breastfeeding.  And, as indicated by this study that was apparently the only one to assess effects of dioxin exposure on neurological development of adolescent children in the general population, increased dioxin exposure apparently has serious effects.  It is especially of note that this study dealt with children old enough to give an indication of long-term effects of the toxins; essentially all of the other studies assessing effects of such toxins, which tested children at much younger ages, took their measurements before long-term effects would be so well demonstrated.

The authors of this study stated, in the expectedly cautious way, “the current study might suggest that exposure to POPs contained in breast milk may present adverse effects in the long term.”

They also stated, “Our findings are basically consistent with those of prospective cohort studies, which showed decreased scores of intellectual or behavioural functions after low-level exposures to some POPs during pregnancy or early infancy.”  Continuing, “These findings are also biologically plausible because POPs are well-known neurotoxicants, even at low doses.” (emphasis and parenthetical expression added)

-- A 2010 review article (Eubig et al., Lead and PCBs as risk factors for attention deficit/hyperactivity disorder, Environ Health Perspect. 2010 Dec;118(12):1654-67. doi: 10.1289/ehp.0901852. Epub 2010 Sep 9) generalized that “children and laboratory animals exposed to lead or PCBs show deficits in many aspects of attention and executive function that have been shown to be impaired in children diagnosed with ADHD, including tests of working memory, response inhibition, vigilance, and alertness.” This should be considered together with knowledge of the tremendous increase in PCB concentrations in children due to breastfeeding, as indicated in the following study: 

Jusko et al.,  Prenatal and Postnatal Serum PCB Concentrations and Cochlear Function in Children at 45 Months of Age, Environmental Health Perspectives, 22 July 2014 (Advance Pub.) at http://ehp.niehs.nih.gov/wp-content/uploads/advpub/2014/7/ehp.1307473.pdf:  This 2014 study found that children at 45 months of age who had been breastfed for 6 to 12  months were found to have over 9 times the PCB concentrations compared with non-breastfed children, with even greater differences if the children had been breastfed for longer.

-- Pluim, H. J. et al. (1994). Clinical laboratory manifestations of exposure to background levels of dioxins in the perinatal period. ACTA Paediatrics, 83, 583-587.  This study examined effects of dioxins in breast milk on newborns and found detectable effects on the liver.  It was unclear whether these effects were necessarily adverse, but detectable effects by a known toxin on an important body organ, while still in infancy, has an implication of unfavorable long-term impact.

*-- A major text published in 2011, with 21 contributing authors (R.C. Gupta, Ed., Reproductive and Developmental Toxicology, Burlington: Elsevier Science, 2011, ISBN: 978-0-12-382032-7, at http://www.sciencedirect.com/science/book/9780123820327), states as follows, referring to dioxins (on p. 551), “early developmental exposures to these chemicals are particularly devastating.”  (on p 559):  “These studies have indicated that … the most susceptible period of exposure is during development and nursing.”….  “Several epidemiological studies have indicated that exposure to PCBs can contribute to hyperactivity and may contribute to the prevalence of attention deficit hyperactivity disorder (ADHD) in humans (Bowman et al., 1981; Rice, 2000; Hardell et al., 2002).” ^(68b) This should be seen in combination with the well-known large multiple by which breastfeeding exceeds formula feeding in causing an infant to ingest PCBs. (see www.breastfeeding-toxins.info)

Since PBDEs may be the most rapidly-increasing of the developmental toxins in human milk, and since they have been found to be over 50 times higher in breast milk than in infant formula (see www.breastfeeding-toxins.info), it is relevant to list here a study that identified mechanisms by which PBDEs apparently disrupt development of the brain:

Betts:   Brain Drain? PBDEs Alter Development of Human Brain Cells,  Environ Health Perspect. Apr 2010; 118(4): A173. PMCID: PMC2854751 at  www.ncbi.nlm.nih.gov/pmc/articles/PMC2854751.   In this study, a team of scientists employed a method for evaluating human developmental neurotoxicity that they had developed, using “primary fetal human neural progenitor cells,” producing “neurospheres,” which undergo the same basic processes that occur during the early stages of normal human brain development.  PBDEs were found to reduce cell migration, an important part of brain development that takes place to a great extent postnatally, especially in the cerebellum.  PBDEs also “interfered with the differentiation of immature progenitor cells into neurons and oligodendrocytes.”  The research team wrote that their data “suggest current (human) PBDE exposure levels are likely to be of concern for human health.”  Other studies have found specific associations of PBDEs in breast milk with ADHD-like traits in exposed children. (see Section 2.b.1) 

Section 2.b.2:  Obesity

Some additional detail is provided concerning these obesity studies, since they provide good illustrations of how misleading the results of the typical observational studies can be, due to confounders that are actual underlying causes of most of the "associations" that are found in observational studies.

As explained in more detail at www.breastfeeding-benefits.net, the studies that are quoted by breastfeeding's promoters have serious weaknesses, including that they are all observational studies and are therefore very subject false conclusions due to confounders.  As indicated in the Surgeon General's Call to Action to Support Breastfeeding and elsewhere, mothers of higher socio-economic strata in the U.S. and much of Europe are far more likely to breastfeed than mothers of lower socio-economic strata.  And obesity is well-known to be far less prevalent in children of mothers of higher socio-economic strata than in children of lower socio-economic strata.^(4c2)   An "association" has been found in those countries between more breastfeeding and less obesity, causing many to think that the reduced obesity results from breastfeeding, rather than from the confounding fact that the breastfed children are disproportionately of the class that always has less obesity.

There are several studies, including two especially large ones, that have taken effective steps to avoid those U.S.-European confounders; and, not surprisingly, those studies have arrived at findings that are the opposite of the studies that are selectively quoted by breastfeeding's proponents.

a)  First note that (1) size of a study is a very important factor in determining its accuracy, and (2) randomization is considered to be the "gold standard" in scientific studies as a means of avoiding the effects of confounders. The largest study yet conducted on the health effects of breastfeeding, published in the Journal of the American Medical Association, was also extremely unusual in utilizing randomization:  the PROBIT study conducted in Belarus, with over 17,000 mother-infant pairs, following the children's outcomes to age 11.5.  The researchers gathered data concerning an experimental group whose breastfeeding rates were greatly increased by major promotion of breastfeeding, comparing that with data from a control group whose breastfeeding was relatively minimal.  The odds ratio for overweight/obesity in the experimental group was 1.18, and the odds ratio for obesity alone only was 1.17. ^(4d)  In other words, there was a 17% increase in likelihood of becoming obese among those children who had been more highly breastfed.  The authors pointed out that their analysis "may underestimate the effect of the true exposure of interest (breastfeeding exclusiveness and duration), owing to overlap in breastfeeding between the randomized groups. (Many intervention mothers did not exclusively breastfeed for 3 or 6 months, whereas some control mothers did)."  Using other statistical methods to analyze their data in different ways (shown in their Table 4), the researchers arrived at alternative figures, in this case comparing children breastfed for less than 3 months with children breastfed for two different periods of greater duration.  Utilizing one of their two means of adjusting their data, they estimated that children breastfed for between 3 and 6 months were about 51% more likely to become obese than those breastfed for less than 3 months, and children breastfed for over 6 months were 98% more likely to become obese than those breastfed for less than 3 months. Using the other of their two ways of adjusting the data for this comparison, the increases linked with progressively greater durations of breastfeeding were 45% and 80%. 

To summarize the data from this uniquely large study, published in a prestigious medical journal, which was also the only study to utilize the recognized best means of avoiding the error-producing effects of confounders:  The findings were analyzed in various different ways, and the only disagreement among their various estimates was as to whether more extensive breastfeeding led to large increases in obesity or extremely-large increases in obesity.  A high proportion of the estimates fell into the extremely-large category. And their estimates showed a dose-response relationship, with progressively greater durations of breastfeeding being linked with progressively greater incidence of obesity.

    b)  A study of 4442 children in Brazil (Pelotas area) considered the contrasting findings in different studies of the relationship between breastfeeding and obesity; it appeared that the contrasting findings depended on the particular characteristics of the societies in which the studies are conducted.  Those differing social characteristics affect the nature of the confounders in the different societies, the confounders that can cause what the AHRQ calls "false conclusions" in typical (observational) studies.^(4a)  This chart shows some data from the ALSPAC study in England, indicating a strong positive relationship between breastfeeding rates and income as that relationship is typically found in the U.S. and much of Europe; it also shows the lack of such a relationship as was the case in Pelotas.  As mentioned, higher socio-economic status is a strong predictor of lower obesity incidence.  Low rates of obesity in the ALSPAC study were found to be associated with high rates of breastfeeding; and many observers saw this as evidence that obesity is reduced by breastfeeding, overlooking the link between low obesity and the higher income levels that are disproportionately characteristic of the high breastfeeders.  Higher income levels are undisputedly a strong predictor of lower obesity,^(4c2) and it is entirely likely that higher income levels were the actual determinant of the reduced obesity among the high breastfeeders.  For the Pelotas children, in a region where there was no confounding by income levels in this regard, the "breastfeeding association effect size" was a positive .14 (meaning obesity increased as breastfeeding increased), compared with a negative .16 in the ALSPAC study. ^(4f)

     c) A study of over 8000 children was conducted in Hong Kong, where the greater likelihood of breastfeeding on the part of more-educated mothers did not exist; the follow-up at age 7 was of over 7000.  That study calculated the relationship between breastfeeding and overweight among children in various different ways, and none of their different calculations found beneficial associations of breastfeeding with obesity incidence.  One of their calculations (results shown in their Table 2, bottom) found that "presence of overweight" among children who had been exclusively breastfed for three or more months was 19% greater than the overweight incidence among children who had never been breastfed.  Another calculation (their Appendix Table A1) found that overweight was 27% greater among children who had been exclusively breastfed for three months or more than among never-breastfed children.^(4e)  In what is a very understated way of discussing the problem of false conclusions arrived at in the U.S.-European studies on effects of breastfeeding, the authors of the Hong Kong study concluded with a "key message:.... Studies in populations with a different confounding structure may be valuable in clarifying and reconciling potentially confounded epidemiological associations."  Again, in a region in which the confounder of income-influenced breastfeeding rates was not present, breastfeeding was associated with significantly increased obesity.

d)  Two other studies analyzed sibling pairs as a means of reducing effects of confounders.  Comparing different health outcomes among members of sibling pairs minimizes confounding due to socio-economic factors, such as the far higher rates of breastfeeding among higher-income mothers and the lower rates of obesity among children of higher income mothers.  As also occurred in the other cases (above) in which effective means were utilized to reduce effects of confounding, the results went in the same direction, in the Michels et al. study:  When comparing siblings both of whom were overweight, the heavier sibling in one of the studies was almost four times as likely to have been breastfed as the lighter sibling.^(4h)  For another sibling study that also found higher risk of obesity among breastfed infants, see the Evenhouse et al. study in Section 1.f .

It is worth reviewing the five studies mentioned above and seeing how similar their results are, all finding increased childhood obesity where breastfeeding is substantially increased, as long as measures are taken to avoid the typical confounders that are present in the U.S. and European studies. The various means of avoiding confounding were (a) randomization (the Belarus study), (b) and (c) by conducting the study in an area where the socio-economic confounders are not the same as they are in the U.S. and Europe, and (d) by means of sibling comparisons.  All were effective in varying degrees at avoiding the effects of confounders, and all led to findings of increased obesity linked with increasing breastfeeding.  It is noteworthy that the study that was by far the largest and that used the "gold standard" for preventing confounding also came up with some results showing extremely high increases in obesity linked with increasing breastfeeding.

The above should be seen in relation to the close, detailed correlations seen (in Section 1 of www.child-obesity.us) between major increases in breastfeeding in the U.S. and major increases in obesity.

There appear to be strong effects of breast milk from diabetic mothers in increasing risk of overweight in the breastfed child, as found in two German studies.  In one of the studies, a positive correlation was found between volume of breast milk consumed by a child of a diabetic mother and the risk of the child's being overweight at age 2.  Among children of diabetic mothers, the percentage of overweight among those who had been fed no breast milk was 13%, the percentage of overweight among those who had been fed "some" breast milk from their mothers was 25%, and the risk of overweight among children who had been fed "only" their mothers' milk was 38%. (Long-term impact of neonatal breast-feeding on body weight and glucose tolerance in children of diabetic mothers, Plagemann A et al., Table 3   Diabetes Care. 2002 Jan;25(1):16-22. Found at http://www.ncbi.nlm.nih.gov/pubmed/11772895)

 In another German study, breastfed offspring of diabetic mothers were again found to have an increased risk of overweight, with an odds ratio of 1.98, an increased risk of 98%. (Long-term impact of breast-feeding on body weight and glucose tolerance in children of diabetic mothers: role of the late neonatal period and early infancy.  Rodekamp E et al., Diabetes Care. 2005 Jun;28(6):1457-62.  Found at http://www.ncbi.nlm.nih.gov/pubmed/15920068) 

Heavier and shorter:  Although the following study was not specifically on the subject of obesity, it did assess physical dimensions of children at 24 months, comparing breastfed vs. non-breastfed children, and found that the breastfed children were both shorter and heavier than the non-breastfed children.  In an era in which obesity is a serious problem and under-nutrition is rare, a finding that a certain kind of feeding leads to children who are both shorter and heavier would appear to be a finding of adverse effect of that feeding type: (Jackson et al., Prenatal and postnatal exposure to polychlorinated biphenyls and child size at 24 months of age,  Reprod Toxicol. 2010 January; 29(1): 25. PMCID: PMC2818264 at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2818264) 

Section 2.c  Other studies that have found apparent adverse effects of breastfeeding: (for easy checking of these studies, there are working links to most of them at footnote 12 of www.pollution-autism.info ) 

Section 2.c.1:  Diabetes-related studies:

Norris JM et al., Lack of association between early exposure to cow's milk protein and beta-cell autoimmunity. Diabetes Autoimmunity Study in the Young (DAISY),  JAMA. 1996 Aug 28;276(8):609-14. In a 1995 study of 293 children in Colorado, it was found that children with an early predictor of type 1 diabetes had been breastfed for an average of 10 months, compared with an average of 8 months for the controls.  

Esfarjani F et al.,  IDDM and early exposure of infant to cow's milk and solid food.  National Nutrition and Food Technology Research Institute, Shaheed Beheshti University, Tehran, IR, Iran. Indian J Pediatr. 2001 Feb;68(2):107-10  at http://www.ncbi.nlm.nih.gov/pubmed/11284175    In this study of 52 diabetic cases and 52 well-matched controls in Iran: " A large (sic) proportion of the diabetic children rather than the control children had been breast-fed, and the risk of IDDM among children who had not been breast-fed was below unity." ("below unity" = below average risk)  

Meloni T, MD et al., IDDM and Early Infant Feeding: Sardinian case-control study    Istituto di Clinica Pediatrica e Neonatologica, University of Sassari Sassari  American Diabetes Assn., Diabetes Care, Copyright © 1997 by the American Diabetes Association   In this study of 100 children in Sardinia (a large island off the Italian peninsula) diagnosed with diabetes between 1983 and 1994, it was found that "a larger proportion of the diabetic children rather than the control children had been breast-fed, and the risk of IDDM among children who had not been breast-fed was below unity (odds ratio [OR] 0.41; 95% CI 0.19–0.91)." (In other words, a bottle-fed infant's risk of becoming diabetic was 41% as high as that of a breastfed infant.)

Mijac et al., Role of environmental factors in the development of insulin-dependent diabetes mellitus (IDDM) in Venezuelan children (in Spanish but good abstract in English), Invest Clin. 1995 June;36(2): 73-82  at http://www.ncbi.nim.nih.gv/pubmed/7548302  In this study of 40 diabetic children and 40 age, sex and race-matched controls, it was found that for "95% of controls vs 65% of IDDM (p<.001), cow's milk was given exclusively from birth, or combined with breastfeeding…;" in other words, it appears that 35% of diabetic children had received only human milk after birth, seven times more than the percentage of non-diabetic children who had received only human milk (5%). 

Savilahti E et al., Early infant feeding and type 1 diabetes.  Eur J Nutr. 2009 Jun;48(4):243-9. doi: 10.1007/s00394-009-0008-z. Epub 2009 Mar 5.  Hospital for Children and Adolescents, University of Helsinki, Helsinki, Finland. In this Finnish study of 6200 children born in 1994-95 with follow-up in 2006, it was found that "early regular daily feeding with cow's milk-based formula tended to associate with lower risk for type 1 diabetes (OR 0.66; 95% confidence interval 0.38-1.13; P = 0.08)."

Telahun M et al., The relation of early nutrition, infections and socio-economic factors to the development of childhood diabetes. Department of Paediatrics and Child Health, Faculty of Medicine, Addis Abeba University. Ethiop Med J. 1994 Oct;32(4):239-44. In this 1990-91 study of 55 patients and 181 controls at two Ethiopian-Swedish hospitals, it was found that "introduction of bottle-feeding was significantly more frequent among unrelated controls at three months of age (9/39 diabetics versus 41/83 controls)."  That is, they found that unrelated non-diabetics were over twice as likely to have been bottle-fed at three months of age as were the diabetics. ^(8o)

The following studies are highly relevant to adverse effects of breastfeeding if one bears in mind that breastfed children have many-times higher levels of PCBs and dioxins than bottle fed children, with higher levels having been found to be in proportion to duration of breastfeeding (see Section 1.a of www.breastfeeding-toxins.info):

1) Longnecker et al.,  Polychlorinated biphenyl serum levels in pregnant subjects with diabetes. Diabetes Care 2001; 24: 1099–1101, at http://care.diabetesjournals.org/content/24/6/1099.full#T2    The authors studied 2,245 pregnant women, 44 of whom had diabetes and found the mean serum PCB level in the women with diabetes to be 30% higher than that in the controls.  The Odds Ratio of having diabetes increased dramatically, in a dose-response relationship, to 2.9, 4.4, and 5.1 with increasing levels of PCBs in the women.

2) Meeker et al., Exposure to polychlorinated biphenyls (PCBs) and male reproduction, Syst Biol Reprod Med. 2010 Apr;56(2):122-31. doi: 10.3109/19396360903443658. at http://www.ncbi.nlm.nih.gov/pubmed/20377311.  This review study found that male reproductive health and testosterone levels were reported in several epidemiological studies to be degraded by increased PCB levels resulting from merely background exposures.  This has special significance in an age of declining birth rates, when many couples are paying large sums of money and incurring risks (for both the children and the mothers) by utilizing artificial reproductive technologies in an effort to achieve conception.

3) Arisawa et al., Background exposure to PCDDs/PCDFs/PCBs and its potential health effects: a review of epidemiologic studies, J Med Invest. 2005 Feb;52(1-2):10-21, at http://www.ncbi.nlm.nih.gov/pubmed/15751269.  In this review of epidemiologic studies, it was reported that “Consistent results have been reported for the association between exposure to background levels of PCBs/dioxins… and defective neurodevelopment of infants in the U.S. and Europe.”

Section 2.c.2:  Studies related to asthma and/or allergies

For very brief summaries of the relevant findings of most of the studies below, go to Section 2 of www.breastfeeding-and-asthma.info.

Benn CS, Breastfeeding and risk of atopic dermatitis, by parental history of allergy, during the first 18 months of life.  Am J Epidemiol. 2004 Aug 1;160(3):217-23. Found at http://www.ncbi.nlm.nih.gov/pubmed/15257994

-  Bergmann RL et al., Duration is a risk factor for atopic eczema.  Clin Exp Allergy. 2002 Feb;32(2):205-9. Found at http://www.ncbi.nlm.nih.gov/pubmed/11929483

-  Carson, Risk factors for developing atopic dermatitis, Dan Med J. 2013 Jul;60(7):B4687, at http://www.ncbi.nlm.nih.gov/pubmed/23809981

-  Colen, Is Breast Truly Best? Estimating the Effects of Breastfeeding on Long-term Child Health and Wellbeing in the United States Using Sibling Comparisons,   in Social Science and Medicine  2014 at http://www.sciencedirect.com/science/article/pii/S0277953614000549

-  Costa Lima et al., Do Risk Factors for Childhood Infections and Malnutrition Protect Against Asthma? A Study of Brazilian Male Adolescents,  Am J Public Health. 2003 November; 93(11): 1858–1864. at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1448063/

-  Chuang CH et al., Infant feeding practices and physician diagnosed atopic dermatitis: a prospective cohort study in Taiwan, Pediatr Allergy Immunol. 2011 Feb; 22(1 Pt 1):43-9. doi: 10.1111/j.1399-3038.2010.01007.x. Found http://www.ncbi.nlm.nih.gov/pubmed/20573037

-  Grandjean P et al., Allergy and Sensitization during Childhood Associated with Prenatal and Lactational Exposure to Marine Pollutants    Environ Health Perspect. 2010 October; 118(10): 1429–1433. PMCID: PMC2957924    found at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2957924  This study found that risk of developing certain allergies increased with each additional month of breastfeeding. 

-  Hong X, J et al.,.Gene polymorphisms, breast-feeding, and development of food sensitization in early childhood. Allergy Clin Immunol, 2011 Aug;128(2):374-81.e2. doi: 10.1016/j.jaci.2011.05.007. Found at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3149737/

-  Kramer et al., Effect of prolonged and exclusive breast feeding on risk of allergy and asthma: cluster randomised trial at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2034727/

-  Mandhane PJ et al., Interactions between breast-feeding, specific parental atopy, and sex on development of asthma and atopy.  J Allergy Clin Immunol. 2007 Jun;119(6):1359-66. Epub 2007 Mar 13. Found at http://www.ncbi.nlm.nih.gov/pubmed/17353035/

For ease of referral to the sources indicated here, if there is no highlighted link, you can (a) use your cursor to drag over and select a URL from the footnote (select the letters beginning with www or http and ending just before the next space; be sure to select all of that but no more, not even a space), then (b) control - c  (to copy that); then (c) paste that (control - v) into the horizontal web-address slot at the top left of your browser page, then press ENTER on your keyboard.

-  Mascola,et al., Exposure of young infants to environmental tobacco smoke: breast-feeding among smoking mothers. Am J Public Health. 1998 June; 88(6): 893–896. PMCID: PMC1508233  found at www.ncbi.nlm.nih.gov/pmc/articles/PMC1508233

-  Matheson MC, et al., Breast-feeding and atopic disease: a cohort study from childhood to middle age.  J Allergy Clin Immunol. 2007 Nov;120(5):1051-7. Epub 2007 Aug 31. Found at http://www.ncbi.nlm.nih.gov/pubmed/17764732

-  Mihrshahi S, et al., The association between infant feeding practices and subsequent atopy among children with a family history of asthma,  Clin Exp Allergy. 2007 May;37(5):671-9. found at http://www.ncbi.nlm.ni Breastfeeding h.gov/pubmed/17456214

-  Miyake Y, et al., Breastfeeding and atopic eczema in Japanese infants: The Osaka Maternal and Child Health Study.  Pediatr Allergy Immunol. 2009 May;20(3):234-41. doi: 10.1111/j.1399-3038.2008.00778.x. Found at http://www.ncbi.nlm.nih.gov/pubmed/19438982

-  Paton J, et al., Infant Feeding Practices and Nut Allergy over Time in Australian School Entrant Children, Int J Pediatr. 2012; 2012: 675724. Published online 2012 July 3. doi: 10.1155/2012/675724 PMCID: PMC3397206 found at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3397206/

-  Perkin et al., Randomized Trial of Introduction of Allergenic Foods in Breast-Fed Infants, N Engl J Med 2016; 374:1733-1743 May 5, 2016m at http://www.nejm.org/doi/full/10.1056/NEJMoa1514210?query=TOC

-  Purvis DJ, et al., Risk factors for atopic dermatitis in New Zealand children at 3.5 years of age.  There was a dose response relationship of more breastfeeding with increased dermatitis.  Br J Dermatol. 2005 Apr;152(4):742-9. http://www.ncbi.nlm.nih.gov/pubmed/15840107

-  Rusconi F, et al.. Risk factors for early, persistent, and late-onset wheezing in young children.  Am J Respir Crit Care Med 1999; found at http://www.atsjournals.org/doi/pdf/10.1164/ajrccm.160.5.9811002

-  Sahakyan A, et al., Feeding practices of babies and the development of atopic dermatitis in children after 12 months of age in Armenia: is there a signal?  Eur J Epidemiol. 2006;21(9):723-5. Epub 2006 Oct 18. Found at http://www.ncbi.nlm.nih.gov/pubmed/17048079

-  Saarinen KM, et al., Infant feeding patterns affect the subsequent immunological features in cow's milk allergy.  Clin Exp Allergy. 2000 Mar;30(3):400-6. at www.ncbi.nlm.nih.gov/pubmed/10691899

-  Salam et al., Early-Life Environmental Risk Factors for Asthma: Findings from the Children’s Health Study, May 2004 • Environmental Health Perspectives, at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1241973/pdf/ehp0112-000760.pdf

-  Sears MR, Long-term relation between breastfeeding and development of atopy and asthma in children and young adults: a longitudinal study.  et al., Lancet. 2002 Sep 21;360(9337):901-7. Found at http://www.ncbi.nlm.nih.gov/pubmed/12354471

For ease of referral to the sources indicated here, if there is no highlighted link, you can (a) use your cursor to drag over and select a URL from the footnote (select the letters beginning with www or http and ending just before the next space; be sure to select all of that but no more, not even a space), then (b) control - c  (to copy that); then (c) paste that (control - v) into the horizontal web-address slot at the top left of your browser page, then press ENTER on your keyboard.

-  Takemura Y et al.,  Relation between Breastfeeding and the Prevalence of Asthma: The Tokorozawa Childhood Asthma and Pollinosis Study,  Oxford Journals Medicine American Journal of Epidemiology Volume 154, Issue 2 Pp. 115-119. American Journal of Epidemiology aje.oxfordjournals.org Am. J. Epidemiol. (2001) 154 (2): 115-119. doi: 10.1093/aje/154.2.115 found at http://aje.oxfordjournals.org/content/154/2/115.abstract?ijkey=119530f7421c3b14e82a501acb68c2f174e4b041&keytype2=tf_ipsecsha

-  Waltraud Eder, M.D., et al, The Asthma Epidemic,  New England Journal of Medicine, N Engl J Med 2006;355:2226-35. Copyright © 2006 Massachusetts Medical Society.found at http://physio.ucsf.edu/GEMS/courses/Immunology/materials/fa11_essential_immunology/september_6_asthma/elder_nejm.pdf

-  Wegienka G, et al., Breastfeeding history and childhood allergic status in a prospective birth cohort.  Ann Allergy Asthma Immunol. 2006 Jul;97(1):78-83. Found at http://www.ncbi.nlm.nih.gov/pubmed/16892786

-  Wright AL et al., Maternal asthma status alters relation of infant feeding to asthma in childhood.  Adv Exp Med Biol. 2000;478:131-7. Found at http://www.ncbi.nlm.nih.gov/pubmed/11065066

*NOTE: The next three studies were found in: Duncan JM, et al., Breastfeeding and allergies: time for a change in paradigm?  Curr Opin Allergy Clin Immunol. 2008 Oct;8(5):398-405. doi: 10.1097/ACI.0b013e32830d82ed. found at www.ncbi.nlm.nih.gov/pubmed/18769191  The authors generalized in the abstract of their review of many studies that “most recent studies do not confirm the 'conventional wisdom' that breastfeeding is protective against allergy and asthma.” (It appears that “do not confirm” is the polite way of saying that the studies actually show the opposite of the conventional wisdom’s belief.)

-  Guilbert TW et al., Effect of breastfeeding on lung function in childhood and modulation by maternal asthma and atopy.  Am J Respir Crit Care Med 2007; 176:843–848.

-  Pesonen M et al., Prolonged exclusive breastfeeding is associated with increased atopic dermatitis: a prospective followup study of unselected healthy newborns from birth to age 20 years.  Clin Exp Allergy 2006; 36:1011–1018.*

-  Wright AL,et al., Factors influencing the relation of infant feeding to asthma and recurrent wheeze in childhood.  Thorax 2001; 56:192–197.

-  Yanagisawa et al., Effects of Maternal Exposure to Di-(2-ethylhexyl) Phthalate during Fetal and/or Neonatal Periods on Atopic Dermatitis in Male Offspring, Environ Health Perspect. Sep 2008; 116(9): 1136–1141. Published online Apr 9, 2008. PMCID: PMC2535612 at  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2535612 “Maternal exposure to a 100-μg dose of DEHP during neonatal periods, but not during fetal periods, enhanced atopic dermatitis-like skin lesions related to mite allergen in males.”

For ease of referral to the sources indicated above, if there is no highlighted link, you can (a) use your cursor to drag over and select a URL from the footnote (select the letters beginning with www or http and ending just before the next space; be sure to select all of that but no more, not even a space), then (b) control - c  (to copy that); then (c) paste that (control - v) into the horizontal web-address slot at the top left of your browser page, then press ENTER on your keyboard.

Section 2.c.3:  Child conduct

Teacher ratings in the following study revealed a significant association between increasing breastfeeding duration and conduct disorder ratings at 7 years:  Fergusson et al., Breastfeeding and subsequent social adjustment in six- to eight-year-old children. J Child Psychol Psychiatry. 1987;28(3):379–386pmid:3597562

Section 2.d

Section 2.d.1:  Or filter your current search General neurological development:

      Gascon et al., Polybrominated Diphenyl Ethers (PBDEs) in Breast Milk and Neuropsychological Development in Infants, in Environ Health Perspect. 2012 December; 120(12): 1760–1765. Published online 2012 September 25. doi: 10.1289/ehp.1205266 PMCID:PMC3548276    At   http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548276.  The researchers found, in a study of 290 breastfed Spanish Children, that those who consumed breast milk containing a variation of PBDEs commonly found in contemporary breast milk (BDE 209) for a breastfeeding period of 16 weeks or less had average negative mental test (BSID) scores of -1.07, and those exposed to it for a breastfeeding period of more than 16 weeks had average negative scores over three times as great (-3.48).  Bear in mind that (a) this showed apparent effects of PBDEs present in the milk of a group of European mothers who were apparently typical except in being more highly educated than average; and (b) American breast milk has been found to be 10 to 100 times higher in PBDEs than the levels found in Europe. (An Exposure Assessment of Polybrominated Diphenyl Ethers. Washington, DC, USA: USEPA; 2010.)

The authors pointed out that their study was larger than previous such studies and that the BSID is one of the most widely used tools available in Spanish to assess neuro-development at such young ages.  They concluded, "Results suggest an association between increasing PBDE concentrations in colostrum, particularly BDE-209, and a worse cognitive development in the first year of life."  They also pointed out, "associations in the longer breastfeeding group may be underestimated because the higher social class and education level of these mothers may provide a more advantageous environment for neuro-development." 

-- Vreugdenhil et al., Effects of Perinatal Exposure to PCBs on Neuropsychological Functions in the Rotterdam Cohort at 9 Years of Age, Neuropsychology, 2004, Vol. 18, No. 1, 185–193  at http://psycnet.apa.org/journals/neu/18/1/185.pdf

This prospective study (therefore allowing accurate measures of exposures, compared with retrospective studies) investigated mental abilities of nine-year-old children in relation to their histories of breastfeeding versus formula feeding; the authors grouped the children into six different categories, according to shorter or longer durations of breastfeeding, formula feeding, and higher or lower exposures of each of those groups to prenatal toxins.  The formula-fed children performed better than their breastfed counterparts, and the children who were breastfed for longer periods performed worse than those breastfed for shorter periods, in scores on a test of executive function.  Those relationships held consistently, when the subjects were grouped according to both higher prenatal exposures to toxins and lower prenatal exposures to toxins.  Scores of formula-fed children were only insignificantly higher than those of children breastfed for shorter durations (6 to 16 weeks)

Describing the test (Tower of London test) that was used in the above study, the authors said, “these tasks are complex, multifactorial tasks, and performance may reflect frontal lobe functions as well as more posterior-related functions. For example, performance on the TOL requires functions such as planning, spatial working memory, attention and response inhibition, and the ability to relate and integrate isolated details into a coherent whole, as well as spatial and motor abilities…. (Such studies) showed activation during performance on the TOL in other brain areas….,” enumerating five other brain areas in addition to the frontal lobe that were observed to be active with this kind of test.  This study apparently provided better evidence of neurological effects of formula-feeding versus breastfeeding than most other studies of effects of breastfeeding, since it tested children at a relatively advanced age (therefore providing better evidence of long-term, lifetime-relevant effects) and since the test was relevant to a greater range of mental activities than typical tests.

-- Lynch et al., The effect of prenatal and postnatal exposure to polychlorinated biphenyls and child neurodevelopment at age twenty four months, Reprod Toxicol. 2012 Nov;34(3):451-6. doi: 10.1016/j.reprotox.2012.04.013. Epub 2012 May 5.  at http://www.ncbi.nlm.nih.gov/pubmed/22569275   “…breast milk exposure to PCB 153 appears to be associated with decrements in motor development.”

    Herbstman et al., Developmental Exposure to Polybrominated Diphenyl Ethers and Neurodevelopment. Curr Environ Health Rep. 2014 Jun 1;1(2):101-112.  at http://www.ncbi.nlm.nih.gov/pubmed/25530937.  This study found that “the majority of the epidemiologic evidence supports that early life exposure to PBDEs measured during pregnancy and/or during childhood is detrimental to child neurodevelopment in domains related to child behavior, cognition, and motor skills.”  This should be noted along with awareness of the high levels of PBDEs in breast milk, as indicated by the estimate that breast-fed infants are exposed to 306 ng/kg body weight/day PDBE compared with 1 ng/kg body weight/day in adults.  (Costa et al., Polybrominated diphenyl ether (PBDE) flame retardants: environmental contamination, human body burden and potential adverse health effects. Acta Biomed. 2008;79(3):172–183.)  Also the reader should be aware of the related differences in PBDE levels between breastfed and formula-fed infants as found in the following study:

Carrizo et al., Influence of breastfeeding in the accumulation of polybromodiphenyl ethers during the first years of child growth. Environ Sci Technol. 2007 Jul 15;41(14):4907-12.at http://www.ncbi.nlm.nih.gov/pubmed/17711201.   The authors observed increases of average body burden of total PBDEs between birth and the first 4 years of 65 and 10 ng for breastfed and formula-fed children, respectively.  (See the other studies just above regarding the special relevance of these differences.)

   Walkowiak J, et al., Environmental exposure to polychlorinated biphenyls and quality of the home environment: effects on psychodevelopment in early childhood.  Lancet. 2001 Nov 10;358(9293):1602-7. Abstract at http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(01)06654-5/abstract     In a study of 171 healthy mother-infant pairs, testing development at various points up to 42 months, and measuring postnatal PCB concentrations, “Negative associations between milk PCB and mental/motor development were reported at all ages, becoming significant from 30 months onwards. Over 30 months, for a PCB increase from the 5th percentile to the 95th percentile, there was a decrease of 8.3 points (95% CI -16.5 to 0.0) in the Bayley Scales of Infant Development mental scores, and a 9.1 point decrease (95% CI -17.2 to -1.02) in the Bayley Scales of Infant Development motor scores. There was also a negative effect of postnatal PCB exposure via breastfeeding at 42 months.”  At that age, the median concentrations of PCBs in children who had been breastfed for over 4 months were found to be almost five times as high as PCB concentrations in children who had been breastfed for two weeks or less.

   Faroon et al., Effects of polychlorinated biphenyls on the nervous system, Toxicol Ind Health. 2000 Sep;16(7-8):305-33.  at http://www.ncbi.nlm.nih.gov/pubmed/11693948   “Monkeys exposed postnatally to PCB mixtures of congeneric composition and concentration similar to that found in human breast milk showed learning deficits long after exposure had ceased.”

   Kirk et al., Perchlorate and iodide in dairy and breast milk.  Environ Sci Technol. 2005 Apr 1;39(7):2011-7. at http://www.ncbi.nlm.nih.gov/pubmed/15871231 Quoting from this study by a team of researchers at The Institute of Environmental and Human Health at Texas Tech University, “Perchlorate inhibits iodide uptake and may impair thyroid and neurodevelopment in infants….  Perchlorate in 47 dairy milk samples from 11 states and in 36 human milk samples from 18 states were measured…. The dairy and breast milk means were, respectively, 2.0 and 10.5 microg/L with the corresponding maximum values of 11 and 92 microg/L….”

    Chien LC, et al., Analysis of the health risk of exposure to breast milk mercury in infants in Taiwan. Chemosphere. 2006 Jun;64(1):79-85. Epub 2006 Jan 25 at http://www.ncbi.nlm.nih.gov/pubmed/16442149  This 2006 study determined that, of the three sources of infant exposure to  mercury (a known neuro-developmental  toxin), ingestion (breast milk), inhalation, and dermal exposure, the largest contribution was from breast milk, providing 96 to 99.6% of the total exposure.

    Winickoff et al., Beliefs About the Health Effects of “Thirdhand” Smoke and Home Smoking Bans  Pediatrics  Vol. 123 No. 1 January 1, 2009  pp. e74 -e79  (doi: 10.1542/peds.2008-2184) at  http://pediatrics.aappublications.org/content/123/1/e74.full   According to this study in the journal Pediatrics, “Similar to low levels of lead exposure, low levels of tobacco smoke markers have been associated with cognitive deficits among children. The highest tobacco exposure levels were associated with the lowest reading scores….”  This should be seen in combination with the finding (quoted and cited in Section 2.f) that breastfed infants of smoking mothers show markers for smoke exposure 10 times higher than bottle-fed infants of smoking mothers.

The following studies are especially relevant in that multiple studies have found PCBs to be many times higher in breastfed than in formula-fed children (see Section 2.g below and Section 1.a of www.breastfeeding-toxins.info):

-- Carpenter, Polychlorinated Biphenyls (PCBs):  Routes of Exposure and Effects on Human Health, Reviews on Environmental Health, Volume 21, No. 1, 2006.

The author concluded that “the higher the child’s exposure to PCBs in early life, the lower the IQ and the more the child exhibits anti-social behavior, depression, and attention deficit hyper-activity disorder-type symptoms. These effects are found over the full range of IQ, however, and even bright kids would have been brighter had they not been exposed.”  See above as well as many other studies pointing out that breast milk is the principal determinant of a child’s PCB levels.

--  Rice and others.  As presented in a document of the U.S. ATSDR, monkeys exposed from birth to age 20 weeks to PCB mixtures of congeneric composition and concentration similar to that found in human breast milk showed learning deficits long after exposure had ceased (Rice 1997, 1998, 1999b; Rice and Hayward 1997, 1999a). This type of study appears to be the most relevant to evaluating risk of PCB exposure by infants since they mimic the exposure scenario for a nursing human infant.”  (U.S. ATSDR document on PCBs, Section 3.7, p. 381, at http://www.atsdr.cdc.gov/ToxProfiles/tp17.pdf)

-- Solomon et al., Chemical Contaminants in Breast Milk: Time Trends and Regional Variability, Environmental Health Perspectives • Volume 110 | Number 6 | June 2002 at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1240888/pdf/ehp0110-a00339.pdf  From that study, “Many studies evaluating PCB levels in women have found concentrations in breast milk that are 4–10 times higher than in blood.”  And “The most serious effects of PCBs are on the brain.  Low-level PCB exposures, particularly before birth, have been linked to lower IQ, hyperactivity, shortened attention span, and delayed acquisition of reading skills (84,85). PCBs interfere with thyroid hormone, and some researchers believe that this mechanism may explain some of the neurologic effects of PCBs (86).  Thyroid hormone is essential for normal growth and development of the brain before birth and throughout infancy. (87).”

--  A report of the Emory University School of Medicine summarized, “Several animal studies …  have consistently shown that exposure to low levels of PCBs similar to the levels commonly found in human breast milk may have negative health effects. These effects include problems with learning, behavior, and memory.” (Emory University School of Medicine Department of Pediatrics:  Polychlorinated Biphenyls (PCBs)  at http://www.pediatrics.emory.edu/centers/pehsu/concern/pcb.html)

-- Jacobson et al., Effects of Exposure to PCBs and Related Compounds on Growth and Activity in Children (Neurotoxicology and Teratology. Vol. 12, pp. 319-326. © Pergamon Press plc, 1990, abstract at http://www.ncbi.nlm.nih.gov/pubmed/2118230 , full-text PDF downloadable at http://phdtree.org/pdf/9052660-effects-of-exposure-to-pcbs-and-related-compounds-on-growth-and-activity-in-children)    The authors found that “The composite activity rating was negatively related to 4-year serum PCB level in a dose-dependent fashion.” (The authors noted that the milk contamination with PCBs was at relatively common levels, and that breastfeeding history was the “principal determinant” of the children’s 4-year PCB body burdens.)  The most exposed children were “about 2-3 times more likely to be rated ’usually quiet and inactive.’” and less than half as likely to be "in action during much of the period of observation."  The authors considered the possibility that the reduction in activity level could lead to improved attention and cognitive performance, but they pointed out that the higher PCB exposure was not associated with better performance on tests for those traits.

-- Karmaus et al., Early Childhood Determinants of Organochlorine Concentrations in School-Aged Children, Pediatric Research (2001) 50, 331–336, at http://www.nature.com/pr/journal/v50/n3/full/pr2001183a.html

Related to the considerable evidence of adverse effects of PCBs in children, this study found “a strong, dose-dependent relationship between the duration of breast-feeding …and the concentration of all five OCs (organochlorines, including PCBs). Of the potential determinants analyzed, more of the variance of the OC concentration is accounted for by breast-feeding than by any other variable.”  Exclusive breast-feeding beyond 12 weeks was associated with a greater-than doubling of PCB concentrations compared with levels in bottle-fed children, which is especially noteworthy considering the relatively advanced ages (7-10) of the children studied.

-  Al-Saleh et al., Mercury (Hg) Exposure in Breast-Fed Infants and Their Mothers and the Evidence of Oxidative Stress, Biol Trace Elem Res (2013) 153:145-154 at http://link.springer.com/article/10.1007%2Fs12011-013-9687-7   This study examined mother-infant pairs, in which none of the mothers had blood mercury higher than the EPA’s estimated relatively safe level.  The authors found that mercury in the breast milk fed to infants affected the excretion of urinary MDA (which is widely used as an indicator of oxidative stress) “in a dose related manner.”  They also found that “more than 48% of breast-fed infants in this study had urinary Hg levels….(at a level that) that may induce oxidative stress.” If the reader is not familiar with oxidative stress, it should be mentioned that oxidation is more widely known (in its slow form, in the case of iron oxidation) as rust; as in the case of a machine that is rusting, oxidation can go on for some time without causing a complete malfunction, but the machine is being gradually degraded.  The above should be read while aware that (a) toxicity from mercury is best known to affect the brain, and (b) infants who are breastfed have been found to have two and three times the mercury levels after six months or a year of breastfeeding, compared with infants who have been bottle fed.(8)

The following study is relevant to neurological development in that thyroid hormones are known to be crucial to proper development of the human brain:  Nagayama et al., Postnatal exposure to chlorinated dioxins and related chemicals on thyroid hormone status in Japanese breast-fed infants, Chemosphere. 1998 Oct-Nov;37(9-12):1789-93.at http://www.ncbi.nlm.nih.gov/pubmed/9828307.     Effects of postnatal exposure to dioxins and PCBs were studied in 36 breast-fed Japanese infants. Estimated intakes of these chemicals from the breast milk “significantly and negatively correlated” with the levels of thyroid hormones in the blood of breast-fed babies.  This should be seen in relation to the finding that human milk is typically over a hundred times higher in dioxin than infant formula, at initiation of breastfeeding (see Section 1.a  of www.breastfeeding-toxins.info).

………………………….

Section 2.d.2 Immune dysfunction:  The above studies all deal with apparent specifically neurological effects of toxins ingested by infants in the early postnatal period.  It should be mentioned that there has been increasing evidence of connections between immunological development and neurological development; one expert team pointed out “the tight connection between development of the immune system and that of the central nervous system,” and also the plausibility that “disruption of critical events in immune development may play a role in neurobehavioural disorders.“ (Hertz-Picciotto et al., Prenatal exposures to persistent and non-persistent organic compounds and effects on immune system development, Basic Clin Pharmacol Toxicol. 2008 Feb;102(2):146-54. doi: 10.1111/j.1742-7843.2007.00190.x.   at www.ncbi.nlm.nih.gov/pubmed/18226068)  In that regard, it is especially relevant that there are 33 studies in this article (in Sections 2.c.1 and 2.c.2 and below) that have found associations of breastfeeding with immunity-related disorders (diabetes, asthma and allergies). 

Kramer et al., Current Status of the Epidemiologic Evidence Linking Polychlorinated Biphenyls and Non-Hodgkin Lymphoma, and the Role of Immune Dysregulation, at Environ Health Perspect. 2012 Aug; 120(8): 1067–1075. at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3440083.  One quote from that study:  “Immune suppression.  Epidemiological studies show that PCBs are associated with modification of both innate and adaptive immunity, including effects on immune cells and signaling molecules, with implications for both immune response and initiation. Such effects are manifested as an increased incidence of infections; insufficient antibody response to vaccination; and changes in immune organs, lymphocyte subsets, and lymphocyte function.”  This study should be read in combination with awareness of the dramatically increased levels of PCBs in breastfed infants compared with non-breastfed, and in children breastfed for longer vs. children breastfed for shorter periods.  (see Section 2.g and  www.breastfeeding-toxins.info.)

Schell et al., Relationships of putative endocrine disruptors to human sexual maturation and thyroid activity in youth, Physiol Behav. 2010 Feb 9; 99(2): 246., Published online 2009 Oct 1. doi:  10.1016/j.physbeh.2009.09.015 PMCID: PMC2813917 at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2813917/  This study found that breastfed youth at average age 13.2 had PCB levels 1.3 times those of non-breastfed youth, and breastfed young adults had significantly higher POP levels (consisting mainly of PCBs) than non-breastfed young adults.  Higher PCB levels (closely linked to breastfeeding history) were associated with higher levels of “a marker of thyroid dysfunction, and a risk factor for autoimmune disease, with a high predictive value.” (citing five studies in evidence of that point)  Some PCBs are potentially estrogenic, and a grouping of four of those was associated with significantly early puberty in girls (which in turn is linked to risk of breast cancer).  The authors said that the measured PCB levels suggested that “effects observed may be relevant to a considerable proportion of the US population.”

Section 2.e:  Autism

    The following study examined data from all 50 U.S. states and 51 U.S. counties and concluded that there was a direct correlation between exclusive breastfeeding and autism, and that the correlation became stronger as duration of exclusive breastfeeding became longer.   Autism rates associated with nutrition and the WIC program.  Shamberger R.J., Phd, FACN, King James Medical Laboratory, Cleveland, OH  J Am Coll Nutr. 2011 Oct;30(5):348-53.  Abstract at www.ncbi.nlm.nih.gov/pubmed/22081621  The full text, including the quoted passages, can be purchased for $7 or reference librarians at local libraries could probably obtain it at no charge. 

   Trends in Developmental, Behavioral and Somatic Factors by Diagnostic Sub-group in Pervasive Developmental Disorders: A Follow-up Analysis, pp. 10, 14   Paul Whiteley (Department of Pharmacy, Health & Well-being, Faculty of Applied Sciences, University of Sunderland, UK), et al.  Autism Insights 2009:1 3-17,  Table 9, going to the following link and finding the link for this study close above the bottom of the list of studies at www.la-press.com/trends-in-developmental-behavioral-and-somatic-factors-by-diagnostic-s-article-a1725).  This U.K. study found that 65% of autistic cases had been exclusively breastfed for four weeks. Two other sources (Patterns of breastfeeding in a UK longitudinal cohort study, Pontin et al., and Infant Feeding 1995, Foster et al.) are compatible in showing a 28% comparable rate of breastfeeding in the general U.K. population.   An identical figure of 28% was found in the U.K. Infant Feeding Survey - UK, 2010 Publication date: November 20, 2012, Chapter 2, at http://www.hscic.gov.uk/catalogue/PUB08694/ifs-uk-2010-chap2-inc-prev-dur.pdf  An almost identical figure was found in the next-earlier U.K. Infant Feeding Survey (2005).

    Breastfeeding and Autism  P. G. Williams, MD, Pediatrics, University of Louisville, and L. L. Sears, MD, presented at International Meeting for Autism Research, May 22, 2010, Philadelphia Marriot  https://imfar.confex.com/imfar/2010/webprogram/Paper6362.html)   This study found a 37% rate of breastfeeding among children diagnosed with autism, as compared with 14% with comparable breastfeeding in that state's (Kentucky's) population; the p-value was .003, meaning three chances out of a thousand that the finding was a result of chance occurrence.

Dodds et al., The Role of Prenatal, Obstetric and Neonatal Factors in the Development of Autism, J Autism Dev Disord (2011) 41:891–902  DOI 10.1007/s10803-010-1114-8, Table 6, at http://autism.medicine.dal.ca/research/documents/2011DoddsetalJAutDevDisord.pdf   This 2010 Canadian study, drawing data from a population-based “clinically-rich perinatal database,” investigated a very large population, nearly 130,000 births.  Data from almost 127,000 of those children (those without identified genetic risk of autism) went into the study’s finding that there was a 25% increased risk of autism among children who were breastfed at discharge from the hospital.

Note that all of the above studies appear to support a finding that, the greater the exposure to breast milk, the greater the level of autism among the breastfed infants.  In the Dodds study, using discharge from the hospital as the dividing line for breastfeeding exposure, there was a 25% higher autism rate among the breastfed children.  In the Whitely study, the duration of breastfeeding used for the comparison was four weeks, associated with a 130% (65/28) higher-than-normal level of autism.  In the Williams study, the duration of breastfeeding used for comparison was a full six months, which was associated with an approximately 175% (37/13.5) higher rate of autism.  That same kind of "direct correlation (of increased autism rates) with the increasing percentage of women exclusively breast-feeding" and with the "longer duration" of breastfeeding was also found in the Shamberger study. 

      Since poor social competence is one aspect of the spectrum of autistic disorders, it may also be of relevance to see the study in Section 2.b.1 (Gascon M et al.) about such effects that apparently resulted from PBDEs via breastfeeding, effects that were not found to result from gestational exposure to PBDEs in the same mothers.

     PCB-95 Modulates the Calcium-Dependent Signaling Pathway Responsible for Activity-Dependent Dendritic Growth, Gary A. Wayman et al., Environmental Health Perspectives • volume 120 | number 7 | July 2012, found at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3404671/pdf/ehp.1104833.pdf  

This 2012 study regarding PCBs (which are a variation of dioxins) and referred to by the NIH described evidence suggesting that "...PCBs are environmental risk factors for ASD.”  And continuing, “There is experimental evidence that developmental exposure to PCB-95 elicits some aspects of ASD, including an imbalance between excitation and inhibition in the auditory cortex of weanling rats (Kenet et al. 2007) and altered social behaviors in rats."  This should be seen in combination with the known very high levels of PCBs in human milk as compared with levels in infant formula. (see the Walkowiak study in Section 2.d) 

The Kenet et al. study, referred to above, fed rat mothers just enough of the toxin “to match the levels of PCB recorded in nursing human mothers in high-PCB-exposure areas of the U.S.” The study noted that the specific form of PCB that they tested is one of the types that “predominate in breast milk samples,” and that “there is as much as a 6.6-fold increase of plasma PCB concentrations in (human) infants who were breastfed for more than 3 months relative to infants who were not breastfed.”

The effects found in the above study were that the baby rats had “grossly distorted development of the primary auditory cortex” of the brain.  According to Dr. M.M. Merzenich (a member of the U.S. National Academy of Sciences, in whose laboratory the experiment was carried out) the infant rats’ brains’ “normal, progressive development was almost completely blocked,” about half of the rats had a “dramatically altered organization of the representations of sound frequency,” and this was “of special interest because the same bizarre abnormalcies have been recorded in autistic individuals.”

The study’s authors also noted that reports of declines of some forms of PCBs in the environment do not necessarily apply to this “more stable and prevalent” type of PCB.   

Dr. Merzenich pointed out that, in addition to PCBs, we should also be concerned about PBDEs, which are “close cousins” of PCBs, and which have been “approximately doubling in concentration in American bodies every 2-5 years;” PBDEs, like PCBs, accumulate especially in fat and breast milk.  He concluded, “If human fetal and infant effects parallel rat impacts, we would predict that there would be a correlation between the PCB/PBDE levels in human breast milk — and in infant blood — with the probability of autism onset.”

For more about the above study, with citations of sources of all above quotes, see Section 3.b of www.autism-studies.net. 

    Another study investigating differences in PCB concentrations resulting from breastfeeding and traits related to autism is the Jusko study in Section 2.g below; this study found close correlation between PCB levels and hearing loss. (This ties in with effects on auditory development found in the Kenet et al. study, above.)  Bear in mind that hearing deficits (and the resulting lack of speech development) are common among those with ASD, and would be expected to contribute to problems in learning, occupational success, and social relationships.

    Studies indicating PBDEs as autism risk factors are relevant, when seen together with knowledge of the far higher levels of PBDEs in human milk than in infant formula (see Section 1.b of www.breastfeeding-toxins.info):    Mini-review:  Polybrominated diphenyl either (PBDE) flame retardants as potential autism risk factors  Anne Messer,  2010 Elsevier   Physiology and Behavior  100 (2010)  245-249    at http://www.ncbi.nlm.nih.gov/pubmed/20100501.

   The following study, finding six times the normal risk of ASD among children whose mothers at time of birth lived near organochlorine pesticide application areas, should be seen combined with awareness of the greatly increased levels of organochlorines in children in relation to duration of breastfeeding (see the Karmaus study in previous section):  EM Roberts et al., Maternal residence near agricultural pesticide applications and autism spectrum disorders among children in the California Central Valley, Environ Health Perspect. 2007 Oct;115(10):1482-9, at http://www.ncbi.nlm.nih.gov/pubmed/17938740/

     Note that autism overlaps with ADHD:  “inattention, impulsivity and hyperactivity are amongst the most frequent associated symptoms of ASD,” according to a German research team).(7)  Therefore information about studies linking breastfeeding with ADHD or attention/hyperactivity symptoms also has considerable relevance to autism. (see Section 2.b.1)

Section 2.f:  Cancer risk

      M A Mascola, et al.,  Exposure of young infants to environmental tobacco smoke: breast-feeding among smoking mothers.  Am J Public Health. 1998 June; 88(6): 893–896. PMCID: PMC1508233  found at www.ncbi.nlm.nih.gov/pmc/articles/PMC1508233    This 1998 study, of 330 mother-infant pairs, suggests that the infant’s vulnerability to effects of atmospheric toxins could be relatively minor unless the infant ingests those toxins in concentrated form, in breast milk.  Specifically, the study found, "breast-fed infants of smoking mothers have urine cotinine levels 10-fold higher than bottle-fed infants whose mothers smoke." (Cotinine is a marker for smoke exposure.)  The high exposure of breastfed infants of smoking mothers to cotinine is especially significant in that serum cotinine has been found to be negatively associated with child cognitive function. (Haynes et al., Manganese Exposure and Neurocognitive Outcomes in Rural School-Age Children: The Communities Actively Researching Exposure Study (Ohio, USA), Environ Health Perspect; DOI:10.1289/ehp.1408993 Oct. 2015, at http://ehp.niehs.nih.gov/1408993)

     Zanieri L, et al., Polycyclic aromatic hydrocarbons (PAHs) in human milk from Italian women: influence of cigarette smoking and residential area.  Chemosphere. 2007 Apr;67(7):1265-74. Epub 2007 Jan 26.  University of Florence, Department of Chemistry,  Florence, Italy. At  http://www.ncbi.nlm.nih.gov/pubmed/17258279    PAHs are known to cause cancer in animals.  This Italian study found PAHs to be much higher in lactating women who smoke.  The specific form of PAH that was investigated in this study was benzo(a)pyrene (BaP), which is classified as a Class 1 carcinogen by the International Agency for Research on Cancer.  There is no determination of a maximum tolerable amount in breast milk, so the Acceptable Daily Intake (ADI) for drinking water was used in the study. "For babies whose mothers belonged to the non-smoker rural category, daily BaP equivalent intake during a six-month nursing period was below the ADI."  But intake of BaP in breast milk by infants of urban smokers showed values "from about seven times, up to 1000 times higher than ADI." (emphasis added)  Breast milk of urban non-smokers was intermediate in concentrations. This study, like the Mascola et al. study above, appears to demonstrate a powerful effect of lactation at taking in environmental toxins in ambient amounts and concentrating them to hazardous levels before transferring them to infants.

Section 2.g:  Recurrent ear infections, and long-term ear function:

Weisglas-Kuperus N, et al., Immunological effects of environmental exposure to polychlorinated biphenyls and dioxins in Dutch school children. Toxicol Lett. 2004 Apr 1;149(1-3):281-5. at http://www.ncbi.nlm.nih.gov/pubmed/15093274.  This study of 167 Dutch school children found that higher postnatal PCB exposure, at environmental levels, was associated with a higher prevalence of recurrent middle ear infections.  (Understanding the significance of the above to this discussion requires awareness of the well-established finding that the overwhelming preponderance of postnatal exposure to PCBs in breastfed children comes from breast milk, and that PCB levels in formula-fed infants are many times lower -- see below.)

This chart from a study published in 2014, (Jusko et al.),(7a) shows the dramatic increase in children’s PCB concentrations that is linked with breastfeeding.  This study found that hearing loss in the children was directly and very closely correlated with postnatal concentrations of PCBs, but it was not at all correlated with prenatal (maternal) concentrations.  (Bear in mind that hearing acuity is fundamental to learning, much or most occupational effectiveness, social relationships, music appreciation and participation, and alertness to signs of danger.)   In this study, OAEs, which are “an effective diagnostic tool for detecting hearing loss,” were measured in children with varying concentrations of PCBs; it was found that the difference between 75^th percentile and 25^th percentile in PCB concentrations (common differences) was associated with a 1.6 decibel decrease in OAE amplitude. With that in mind, note that a 3 decibel decrease is the equivalent of reduction in sound power by 50%;(7b) it would be likely that breastfeeding in the top10% could result in a full 3 decibel decrease in sound power compared with no breastfeeding.  Note in the above chart that the average difference in PCB concentrations between a non-breastfed child and an average child breastfed for 6 to 12 months was found to be about 850%.  This is compatible with information from various other studies.(7c)

Section 2.h:  SIDS-related studies, finding no benefit of breastfeeding  (These are not counted toward the total number of studies, itemized above, that found adverse effects of breastfeeding)

As related in more detail in Section 9 of www.breastfeedingprosandcons.info,  in the major review that is often cited by breastfeeding’s promoters, there were only three studies of SIDS in relation to breastfeeding that were considered to be of high quality, and two of those three found no benefit of breastfeeding.  The only study that did find a benefit of breastfeeding did an obviously poor job of adjusting for known confounders.  That review also referred to six other studies that made adjustments for known confounders, and four of those six found no benefit of breastfeeding.

Section 2.i:  Studies indicating predominantly postnatal, not prenatal, effects of toxins that are especially heavily present in breast milk:

Jusko et al., Pre- and Postnatal Polychlorinated Biphenyl Concentrations and Longitudinal Measures of Thymus Volume in Infants    Environ Health Perspect. 2012 April; 120(4): 595–600. PMCID: PMC3339462. doi:  10.1289/ehp.1104229 at  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3339462/

In this study supported by both the NIH and the European Commission, the authors stated that “TCDD (dioxin) and (the related chemical) dioxin-like PCBs have well-established effects on the immune system, one of which is thymic atrophy, an outcome observed in all species evaluated after TCDD exposure.” (The thymus “is necessary in early life for the normal development of immunologic function.” (Farlex Partner Medical Dictionary))  In their study of over 900 Slovakian mother-infant pairs, these investigators observed that maternal PCB concentration (therefore prenatal exposure of the infant) had no correlation with the size of the thymus at 6 or 16 months of age; but the infant’s PCB concentration at 6 months of age was associated with a significant decrease in the size of the thymus at that age. The effect of PCBs in reducing the size of the thymus at the 6-month point was so substantial (in relation to the effect associated with prenatal exposure to PCBs) that the authors concluded that their “results suggest that 6 months of age is … the period of greatest sensitivity to PCBs.”  They pointed out that this finding of distinctly postnatal sensitivity of the thymus to toxins was also observed in other studies. Being aware of the special early-postnatal vulnerability of this gland that is necessary for development of immunological function, also note that (as stated in Section 1.a of www.breastfeeding-toxins.info) PCB levels in children who had been breastfed for at least 12 weeks were found to be still over twice as high as in bottle-fed children even at 7 years of age; therefore 6-month postnatal PCB levels in breastfed children appear to be basically attributable to breastfeeding exposures.

Huisman et al., Perinatal exposure to polychlorinated biphenyls and dioxins and its effect on neonatal neurological development, Elsevier, Early Human Development, 41 (1995)111-127,  at http://www.sciencedirect.com/science/article/pii/037837829401611R    This Dutch study of 418 mother-infant pairs found that prenatal exposure to dioxins and PCBs did not show a correlation with postnatal neurological optimality, whereas “only breast-fed children who were perinatally exposed to higher dioxin, mono-ortho PCB, di-ortho PCB and total PCB/dioxin TEQ values showed a reduced neonatal neurological optimality.”

For many studies that have found PCBs to be far higher in breastfed children than in formula-fed children, see Section 2.j below.  Those should be linked with the many studies finding harmful effects of PCBs on neurological development, in Section 1.a of www.breastfeeding-vs.formula.info.

For many other studies that found harmful effects of postnatal toxic exposures while finding no effects of prenatal exposures to those same toxins, see Section 3 of www.autism-research.net/postnatal-effects.htm.

Section 2.j: Studies indicating high levels of important developmental toxins in breastfed as opposed to bottle fed infants:

-- Kirk et al., Perchlorate and iodide in dairy and breast milk.  Environ Sci Technol. 2005 Apr 1;39(7):2011-7. at http://www.ncbi.nlm.nih.gov/pubmed/15871231

Quoting from a 2005 study by a team of researchers at The Institute of Environmental and Human Health at Texas Tech University, “Perchlorate inhibits iodide uptake and may impair thyroid and neurodevelopment in infants….  Perchlorate in 47 dairy milk samples from 11 states and in 36 human milk samples from 18 states were measured…. The dairy and breast milk means were, respectively, 2.0 and 10.5 microg/L with the corresponding maximum values of 11 and 92 microg/L….  The presence of perchlorate in the milk lowers the iodide content and may impair thyroid development in infant.”  Bear in mind that proper thyroid function is important to neurological development.

-- Ettinger et al. (2014), Maternal Blood, Plasma, and Breast Milk Lead: Lactational Transfer and Contribution to Infant Exposure, Environ Health Perspect; DOI:10.1289/ehp.1307187 at http://ehp.niehs.nih.gov/1307187\    -- This study by an international team of ten scientists, published in Environmental Health Perspectives, found that   “a 1-μg/L increase in breast milk lead increased infant blood lead… among infants exclusively breastfed in the previous month (2.2 μg/dL) compared with breastfeeding infants who were not exclusively breastfed in the preceding month (1.1 μg/dL)”.(66)  It should be safe to assume that “no breastfeeding” would have still greater impact in reducing increases in infant blood lead, compared with merely going from exclusive breastfeeding to partial breastfeeding.

-- Lozoff B et al. 2009. Higher infant blood lead levels with longer duration of breastfeeding. J Pediatrics 155(5):663–667.  This study reported that longer breastfeeding was associated with higher infant lead concentrations in three countries, in three different decades, in settings with differing breastfeeding patterns, environmental lead sources, and infant lead levels.“ 

-- Gulson et al., Relationships of lead in breast milk to lead in blood, urine, and diet of the infant and mother. Environ Health Perspect 106:667–674, at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1533188/pdf/envhper00533-0085.pdf  Breast milk was found to be a strong correlate of infant blood lead levels, whereas formula lead correlated poorly with infant blood lead levels.  (See “Relationships of Breast Milk to Other Indices” section near end.)  The authors attributed the lack of correlation of formula lead with infant blood lead to measurement difficulties, but it is entirely possible that, as Ettinger et al. (2014, see above) point out, “to the extent that lead can be found in infant formula, the relative bioavailability of such lead may be less than that of lead in breast milk.” (for a reason they explain)

--  Ettinger et al., (2004) Effect of breast milk lead on infant blood lead levels at 1 month of age, Environ Health Perspect. 2004 Oct; at http://www.ncbi.nlm.nih.gov/pubmed/15471729.   This 2004 study in Mexico found that the difference between lead levels in breast milk that were average for the top quartile and the average for the bottom quartile (a common difference, present in a large part of the population) accounted for a 20% increase in an infant’s lead levels after just one month of breastfeeding.

-- Haynes et al., Manganese Exposure and Neurocognitive Outcomes in Rural School-Age Children: The Communities Actively Researching Exposure Study (Ohio, USA), Environ Health Perspect; DOI:10.1289/ehp.1408993 Oct. 2015, at http://ehp.niehs.nih.gov/1408993/   This study found that serum cotinine has been found to be negatively associated with child cognitive function, which is significant to breastfeeding in that breast-fed infants of smoking mothers have been found to have urine cotinine levels 10-fold higher than bottle-fed infants whose mothers smoke. (See the Mascola et al. study in Section 2.f)

-- PCBs:  See the Jusko et al. study above in Section 2.g, the Walkowiak study in Section 2.d.1, and the several studies indicating substantial PCBs present in breastfed children (as opposed to non-breastfed children), even in mid-childhood and adolescence, in Section 1.a in www.breastfeeding-toxins.info.  For information about harmful effects of PCBs on neurological development, see Section 1.a of www.breastfeeding-vs.formula.info.

Section 2.k:  Reduction of testosterone, with serious implications for cognitive development and for the viability of modern societies:

Since development of the brain is known to be dependent on testosterone(9), the following studies are relevant to neurological development:

    Mocarelli et al., Perinatal Exposure to Low Doses of Dioxin Can Permanently Impair Human Semen Quality, Environ Health Perspect. May 2011; 119(5): 713–718. Published online Jan 24, 2011. doi:  10.1289/ehp.1002134  at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3094426/  In this 2011 study, by 13 scientists, it was found that the median levels of dioxins in breastfed infants were doubled within 4-5 months after birth, compared with levels in formula-fed infants that were reduced by half in that same period of time; after those infants had grown to ages ranging from 18 to 26, average dioxin concentrations were still twice as high in the breastfed young men as in those who had been formula fed.   Breastfed sons born to mothers who had received “modest” increases of dioxin exposure had greatly decreased sperm concentrations relative to the breastfed comparison group (36 million vs. 86 million sperm/mL; p = 0.002).  By contrast, sperm concentrations of the formula-fed exposed and comparison groups were not significantly different from each other.  It should be noted that reproductive function was all that this study was investigating; bear in mind that testosterone (closely related to sperm production) is also known to be important to development of the brain. 

    Schell et al., Relationships of Polychlorinated Biphenyls and Dichlorodiphenyldichloroethylene (p,p’-DDE) with Testosterone Levels in Adolescent Males,   Environ Health Perspect; DOI:10.1289/ehp.1205984 at http://ehp.niehs.nih.gov/1205984  This study of 120 adolescent human males found that  a 10% increase in exposure to PCBs was associated with a 5.6% decrease in testosterone.  These results were said by the authors to be consistent with many other studies’ findings:  four experimental animal studies and six studies of humans. The ratio found in this study should be seen in relation to findings from various studies about the large differences in PCB levels among children:  In children in this same age range in the same population group that was covered in the Schell study just cited, levels of PCBs were about 30% higher among youths who had been breastfed than in those who had not been breastfed.(10))  The Walkowiak study(3c) quoted earlier found PCB levels in 3½-year-old children to be nearly 400% higher in infants who had been breastfed for at least four months, compared with those who had been breastfed for two weeks or less.  A 2006 study found PCB levels to be 13 times as high in breastfed as in bottle-fed infants at six months (that is, a 1200% increase compared with bottle-fed infants).(9a)  So there is good evidence that breastfeeding in contemporary industrialized countries

(a) leads to PCB levels high enough to substantially reduce availability of a hormone that is important to development of the brain; and

(b) the effects of that would be especially great during the early postnatal period, since that is the time when the highest PCB levels occur, and also the time when the brain is going through its most rapid (and most vulnerable) period of development. 

The last figure quoted above was determined in a 2006 study that found PCB levels in breastfed German infants to be as high as had been measured in Germany in the 1980’s, despite the decades-earlier discontinuation of use of PCBs in manufacturing. 

The major reduction of testosterone in males that is linked to breastfeeding has important implications beyond the cognitive abilities that would be affected.  Most industrialized countries currently have birth rates below replacement levels, with many of them far below replacement levels.   Low birth rates are causing serious concerns about the long-term viability of societies with both aging populations and major future declines in numbers of people of working age; among other concerns, social security systems are funded by current contributions from working people, with dramatic projected increases in the number of retirees supported by every ten workers.  An infant feeding that reduces testosterone would inevitably reduce the sexual attraction that males feel toward females, and probably also reduce the attraction that females feel toward males, as well as hindering sexual functioning and reducing the percentage of successful fertilizations.

The above-mentioned low birth rates would be even lower except for major ongoing expenditures on Assisted Reproductive Technologies, which result in over 65,000 births per year in the U.S. alone, not even counting results of non-ART infertility treatments.  Significantly, the births produced by these technologies are also accompanied by enough health problems for both the infants and the mothers that the CDC (in a low-key way) refers to them as “public health challenges.”(11))  There is probably no way to know how greatly low testosterone contributes to the widespread inability to conceive that leads to those birth-producing efforts and the accompanying health problems, as well as to the deficit of births.  Remember from above the basic pattern that appears to be underlying the fertility problems:

-- The increased breastfeeding is transmitting toxins that are widespread in modern industrial societies,   which leads to

--  increased PCBs in infants,   which leads to

--  decreased testosterone,   which leads to

--  reduced birth rates. 

The major efforts and expenditures intended to stimulate births, the health problems that result from the effects of those practices, and the shortage of births are all in addition to the effects of reduction of testosterone on development of children’s brains, described earlier.  And all of the above are in addition to other long-term effects of PCBs described in the next section.

Section 2.l:  General health effects:  The following study is relevant to general adverse effects of breastfeeding if one bears in mind that breastfed children have many-times higher levels of PCBs than bottle fed children, with higher levels having been found to be in proportion to duration of breastfeeding (see Section 1.a of www.breastfeeding-toxins.info):  Carpenter, Polychlorinated Biphenyls (PCBs): Routes of Exposure and Effects on Human Health, Reviews on Environmental Health, Volume 21, No. 1, 2006, at http://www.ncbi.nlm.nih.gov/pubmed/16700427     The conclusion of this study, which reviewed the relationship of a number of different health areas to PCB levels, concluded, “Polychlorinated biphenyls alter the functioning of many different organ systems in both animals and humans and are risk factors for a large number of human diseases.”

     P. Grandjean et al., Attenuated growth of breast-fed children exposed to increased concentrations of methylmercury and polychlorinated biphenyls,  FASEB J. (February 5, 2003) 10.1096/fj.02– 0661fje at www.fasebj.org/content/17/6/699.full.pdf   Greater attenuation of growth was found to associated with each additional month of breastfeeding.   Although there is some question as to whether attenuated physical growth in itself is necessarily unfavorable, a finding that the reduced growth is directly linked to known neurodevelopental toxins contained in breast milk (mercury and PCBs) carries strong implications of neurological harm connected with that exposure.  

Section 3:  Other long-term detrimental effects:

Some researchers have been unable to find harmful effects on young children resulting from the undisputed major increases in children’s concentrations of PCBs that are linked to breastfeeding. The failure of those researchers to observe harmful effects could relate to lack of consideration of important confounders as follows:  women who breastfeed in the cultures where the testing took place are normally of a higher socio-economic status and also non-smokers, giving genetic and environmental advantages to their children. (see www.breastfeeding-benefits.net)  At least as significant, however, are the probable long-term physical as well as neurological effects of the toxins transmitted by breastfeeding, effects that would usually not be observed by the researchers who don’t see harmful effects of toxins on children.  Long-term effects include the following:  breastfed children are much more likely to become obese (see “Obesity” above as well as www.breastfeeding-and-obesity.info), have asthma and/or allergies (see Sections 2.a and 2.c.2 above), have diabetes (see “Diabetes” above and www.breastfeeding-and-diabetes.info), or have serious long-term neurological effects resulting from high PCB levels caused by breastfeeding (more on this to follow).  The four studies that found correlations between duration of breastfeeding and autism prevalence (Section 2.e) did not limit their observations to the first few years of the child’s life.

Various long-term effects of PCBs (remember, 4½ times as high in breastfed children as in formula fed at age 3½) are indicated by the following: “Several studies have evaluated associations of PCBs with human health effects and have demonstrated adverse reproductive (Leoni et al. 1989), developmental (Jorissen 2007), immunologic (Glynn et al. 2008), and neurologic (Prince et al. 2006) effects…. The ability of PCBs to accumulate in brain tissue (Caudle et al. 2006; Saghir et al. 2000; Sipka et al. 2008) is likely related to their neurotoxicity…. Further, epidemiologic studies support an association between PCB exposure and central nervous system disease, including Parkinson disease, amyotrophic lateral sclerosis, non–Alzheimer-related dementia, and brain cancer in adults (Caudle et al. 2006; Hopf et al. 2009; Steenland et al. 2006). The BBB (blood brain barrier) breakdown is a commonality in all of these central nervous system disease states (Weiss et al. 2009)”;  (Above quotations from Seelbach et al., Polychlorinated Biphenyls Disrupt Blood–Brain Barrier Integrity and Promote Brain Metastasis Formation,   Environ Health Perspect. 2010 April; 118(4): 479–484. PMCID: PMC2854723  at  www.ncbi.nlm.nih.gov/pmc/articles/PMC2854723)

A large study published in January, 2014, using data from The National Health and Nutrition Examination Survey (NHANES), arrived at findings suggesting that “PCB neurotoxicity may contribute to cognitive deficits in older persons,” even if the exposures are “at levels generally considered to pose low or no risk.”  And “furthermore, exposure to PCBs was associated with an increased risk of type 2 diabetes among Nurses’ Health Study participants (Wu et al. 2012), and type 2 diabetes is itself a strong risk factor for cognitive impairment and dementia (Strachan et al. 2011). Finally, PCBs were associated with hypertension….”  The study also found that, among women 70-84 years of age, those in the group with the top third of PCB levels had a decrease in cognitive scores (compared with those in the bottom third) “comparable to the difference in cognitive scores between participants in our study who were 8.8 years apart in age.” (Bouchard et al., Polychlorinated Biphenyl Exposures and Cognition in Older U.S. Adults: NHANES (1999–2002), Environ Health Perspect; DOI:10.1289/ehp.1306532 Jan. 2014 at http://ehp.niehs.nih.gov/1306532)

After reading about the effects of PCBs at older ages, remember the above-described persistence of PCBs in the body and remember the expert statement, “manifestations of damage emerge only after compensatory processes have been exhausted….  Most observers agree that the appearance of clinical signs is merely the ultimate phase of a neurodegenerative process whose inception might even be traced to events occurring during early development….  Over time, the aging process will further reduce the number of cells until those that remain are too few to sustain function, and overt effects then erupt.”^(3d1)

Long-term effects of infant exposures to low doses of dioxins, probably from breastfeeding:  See the Lee et al. study in the ADHD section, Section 2.b.1

A Dutch study (Vreugdenhil et al., in Section 2.d.1) found that longer breastfeeding duration was associated with lower scores in 9-year-olds on a test of problem solving.

Referring to an earlier study, a 2014 study in the journal Pediatrics (Lind et al., in Section 2.b.1) reports that teacher ratings revealed a “significant association between increasing breastfeeding duration and conduct disorder ratings at 7 years.”^(66e)

The above is only a partial listing of the studies that have found neurological deficits or other adverse outcomes associated with breastfeeding when the children were followed to older ages, compared with the short time horizons of almost all of the studies that have found no adverse effects of breastfeeding.

Section 4:  Studies indicating hazardous exposures to developmentally-toxic dioxins and PCBs:

In most of the studies from here to the end of this section, children’s exposures to toxins were assessed, but the studies did not include investigation of later health outcomes. However, all of the following studies found breastfed infants to be ingesting dioxins (developmental toxins) in the milk in concentrations that were scores to hundreds of times higher than the EPA-determined relatively safe threshold for non-cancer effects (see second paragraph after this paragraph).  The concentrations were also many thousands of times higher than the safe level for cancer effects (.006 pg/kg-d, as it was apparently determined by the EPA as of the late 1990’s ⁵).  It seems prudent to consider these studies to be evidence of adverse health effects of breastfeeding on the grounds that they indicated that toxic contents of contemporary breast milk vastly exceed the EPA-determined safe level; but these authoritatively-designated hazardous levels of developmental toxins in recent breast milk should especially be considered to be adverse in an era in which most or all of these countries are going through unexplained epidemics of childhood diabetes as well as unexplained dramatic increases in autism and ADHD.  These studies were all published in or very close to the 2000’s, and all arrived at similar figures; the major deviations were in Japan, where a major part of the figures were even higher than the general range, and China, where the exposure was well below the general range in a study of 12 provinces but still 20 to 70 times the 0.7 pg per kg of body weight per day EPA-estimated safe level for non-cancer effects.

     U.S. EPA. Estimating Exposure To Dioxin-Like Compounds - Volume I: U.S. Environmental Protection Agency, Washington, D.C., EPA/600/8-88/005Ca., 2002, revised 2005 – http://cfpub.epa.gov/si/si_public_record_Report.cfm?dirEntryID=43870,  Section II.6, "Highly Exposed Populations" (nursing infants are considered to be one of the highly-exposed populations), 4/94 (p. 39)  "Using these procedures and assuming that an infant breast feeds for one year, has an average weight during this period of 10 kg, ingests 0.8 kg/d of breast milk and that the dioxin concentration in milk fat is 20 ppt of TEQ, the average daily dose to the infant over this period is predicted to be about 60 pg of TEQ/kg-d." 

     Also http://www.epa.gov/iris/supdocs/dioxinv1sup.pdf  in section 4.3.5, at end of that section, "...the resulting RfD in standard units is 7 × 10−10 mg/kg-day."  (that is, O.7 pg of TEQ/kg-d)   In the EPA’s “Glossary of Health Effects”, RfD is defined:  “RfD (oral reference dose): An estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure of a chemical to the human population (including sensitive subpopulations) that is likely to be without risk of deleterious noncancer effects during a lifetime.

     The following U.S. study found typical breastfed infants (during early breastfeeding) to receive over 300 times the 0.7 pg EPA-determined safe threshold of dioxins: Lorber et al.,  Infant Exposure to Dioxin-like Compounds in Breast Milk, Volume 110 | Number 6 | June 2002 • Environmental Health Perspectives (a peer-reviewed journal published by the National Institute of Environmental Health Sciences of NIH)  http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=54708#Download

       Also   J Grigg,  Environmental toxins; their impact on children’s health, Arch Dis Child 2004;89:244-250 doi:10.1136/adc.2002.022202 at http://adc.bmj.com/content/89/3/244.full  (re U.K. levels)

     Also  Wittsiepe J, PCDD/F and dioxin-like PCB in human blood and milk from German mothers. Chemosphere. 2007 Apr;67(9):S286-94. Epub 2007 Jan 10. http://www.ncbi.nlm.nih.gov/pubmed/17217986

       Also  Chovancová J, et al., PCDD, PCDF, PCB and PBDE concentrations in breast milk of mothers residing in selected areas of Slovakia   Chemosphere. 2011 May;83(10):1383-90. doi: 10.1016/j.chemosphere.2011.02.070. Epub 2011 Apr 6. At  www.ncbi.nlm.nih.gov/pubmed/21474162

For ease of referral to the sources indicated here, if there is no highlighted link, you can (a) use your cursor to drag over and select a URL from the footnote (select the letters beginning with www or http and ending just before the next space; be sure to select all of that but no more, not even a space), then (b) control - c  (to copy that); then (c) paste that (control - v) into the horizontal web-address slot at the top left of your browser page, then press ENTER on your keyboard.

         Also: Nakatani T, et al., Polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls in human milk in Osaka City, Japan   Arch Environ Contam Toxicol. 2005 Jul;49(1):131-40. Epub 2005 Jun 22.  Found at http://link.springer.com/article/10.1007%2Fs00244-004-0051-y#page-1

       Also:  Deng B, et al., Levels and profiles of PCDD/Fs, PCBs in mothers' milk in Shenzhen of China: estimation of breast-fed infants' intakes.Environ Int.  2012 Jul;42:47-52. doi: 10.1016/j.envint.2011.03.022. Epub 2011 Apr 30.  (least TEQ EDI of all of these studies, at 48.2 pg TEQ/kg

      Also:  Yang J, et al., PCDDs, PCDFs, and PCBs concentrations in breast milk from two areas in Korea: body burden of mothers and implications for feeding infants. Chemosphere. 2002 Jan;46(3):419-28.  Found at http://www.ncbi.nlm.nih.gov/pubmed/11829398

     Also:  Bencko V et al., Exposure of breast-fed children in the Czech Republic to PCDDs, PCDFs, and dioxin-like PCBs. Environ Toxicol Pharmacol. 2004 Nov;18(2):83-90. doi: 10.1016/j.etap.2004.01.009. Abstract at http://www.ncbi.nlm.nih.gov/pubmed/21782737

    Also:  J Grigg,  Environmental toxins; their impact on children’s health, Arch Dis Child 2004;89:244-250 doi:10.1136/adc.2002.022202 at http://adc.bmj.com/content/89/3/244.full   Data quoted in a British Medical Journal publication of 170 pg in breast milk at two months after birth.

For ease of referral to the sources indicated here, if there is no highlighted link, you can (a) use your cursor to drag over and select a URL from the footnote (select the letters beginning with www or http and ending just before the next space; be sure to select all of that but no more, not even a space), then (b) control - c  (to copy that); then (c) paste that (control - v) into the horizontal web-address slot at the top left of your browser page, then press ENTER on your keyboard.

      S Patandin et al.,  Effects Of Environmental Exposure To  Polychlorinated Biphenyls And Dioxins On Growth And Development In Young Children:  A Prospective Follow-Up Study Of Breast-Fed And Formula-Fed Infants From Birth Until 42 Months Of Age  at   http://Repub.Eur.Nl/Res/Pub/19721  In Table 3.4 of this Dutch study, average dioxin toxic equivalency ingested by breastfed infants 0-6 months of age was found to be 118 pg per kg of body weight per day; at 3.5 years, children in the breast-fed group had PCB levels that were nearly 4 times higher than the PCB levels measured in the formula-fed group (0.75 vs 0.21 pg/L, Table 3.1)

Quinn et al., Investigating Intergenerational Differences in Human PCB Exposure due to Variable Emissions and Reproductive Behaviors,  Environ Health Perspect. May 2011; 119(5): 641–646. at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3094414/.  This study is the source of the chart on the left, showing the difference (in the gray area) between PCB exposures via 6 months of breastfeeding and via infant formula.  PCBs were banned from most manufacturing in the U.S. in 1978, and the authors (recognizing a subsequent decline in PCB levels) worked with a method for determining PCB exposures “that produced estimates that were most consistent with the observed time trends,” so this chart (in this 2011 study) should be reasonably representative of actual exposures to PCBs continuing into the 21^st Century.  The U.S. ATSDR notes that PCBs in the environment declined greatly in the 1980’s, but that they are very persistent in the environment; they also say (in a year 2000 document) that “For most young children, it appears that the dietary intake of PCBs has reached a steady state in the United States.” (Food is recognized to be by far the principal source of PCB exposure.) (U.S. ATSDR, Toxicological Profile for Polychlorinated Biphenyls (PCBs), Nov. 2000, at http://www.atsdr.cdc.gov/toxprofiles/tp17.pdf)  According to a 2013 study, “TEQs (toxic equivalencies) including only PCB contribution did not decrease over time.” (from the first measurement in 1992 through 2010)  (Consonni et al., Blood levels of dioxins, furans, dioxin-like PCBs, and TEQs in general populations: a review, 1989-2010, Environ Int. 2012 Sep;44:151-62. doi: 10.1016/j.envint.2012.01.004. Epub 2012 Feb 24. at http://www.ncbi.nlm.nih.gov/pubmed/22364893)

. . . . . . . . . . . . .

Comments or questions are invited.  At the next link are comments and questions from readers, including a number of doctors.  Some of the doctors have been critical but at least four have been in agreement with us, including two with children of their own with health problems and one who says she has delivered thousands of babies; they put into briefer, everyday language and personal terms some important points that tend to be immersed in detail when presented in our own publications.  Also, we have responded to many readers’ questions and comments, including about having breast milk tested for toxins and about means of trying to achieve milk that is relatively free of toxins, including the “pump and dump” option.  To read the above, with a link for sending your own comments or questions, go to www.pollutionaction.org/comments.htm   If you have criticisms, please be specific about any apparent inaccuracies, rather than merely saying you don’t like what is said here.  Note that we don’t feel obligated to present the favorable side of the breastfeeding debate, since that is already very amply (and one-sidedly) presented in many other, widely-distributed publications as well as in person by numerous enthusiastic promoters. 

_________________________ 

ENDNOTES

(1)  at www.surgeongeneral.gov/library/calls/breastfeeding/calltoactiontosupportbreastfeeding.pdf.

(2) Users’ Guide to the Medical Literature, A Manual for Evidence-based Clinical Practice, Second Edition, copyright 2008, American Medical Association. Published by McGraw Hill.

(2a) Dodds et al., The Role of Prenatal, Obstetric and Neonatal Factors in the Development of Autism, J Autism Dev Disord (2011) 41:891–902  DOI 10.1007/s10803-010-1114-8, Table 6, at http://autism.medicine.dal.ca/research/documents/2011DoddsetalJAutDevDisord.pdf

(2b) "Breastfeeding is not as beneficial as once thought" (06.01.2010) published by the Norwegian University of Science and Technology, at http://www.ntnu.edu/news/breastfeeding   Quoting especially Professor Sven M. Carlsen, Manager of Unit for Applied Clinical Research, Department of Cancer Research and Molecular Medicine, Faculty of Medicine, NTNU.

(2c) “Autism often not diagnosed until age 5 or older”, in U.S. News and World Report 2/24/2012, at http://health.usnews.com/health-news/news/articles/2012/05/24/autism-often-not-diagnosed-until-age-5-or-older-us-report

(2d) U.S. CDC Data and Statistics on ADHD, at http://www.cdc.gov/ncbddd/adhd/data.htm

(2e) see www.mercury-effects.info, including Section F

(3)  The researcher referred to here is a relative of the author of this article, and her personal history is known via personal communication with another relative, so identifying her and her study in a publication such as this might be considered a betrayal of confidence.  However, if a reader has good reason to want to be able to verify what was stated above, specifics could be provided after consultations with the parties involved.  Write to dm@pollutionaction.org.

(3-0) Schantz et al., Effects of PCB Exposure on Neuropsychological Function in Children   Environmental Health Perspectives, 2003, Vol. 111 at at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1241394/pdf/ehp0111-000357.pdf   p. 363

(3a) Grandjean P, et al., Milestone development in infants exposed to methylmercury from human milk, Neurotoxicology. 1995 Spring;16(1):27-33. at http://www.ncbi.nlm.nih.gov/pubmed/7603642;

(3a0) Murata K et al., Delayed brainstem auditory evoked potential latencies in 14-year-old children exposed to methylmercury. J Pediatr. 2004 Feb;144(2):177-83.

(3a1) Evidence Report/Technology Assessment Number 153  Breastfeeding and Maternal and Infant Health, Outcomes in Developed Countries  Prepared for:  Agency for Healthcare Research and Quality   quote from "Structured Abstract" section

(3a2)  This according to John Ioannidis, chair in Disease Prevention at Stanford University School of Medicine, professor of medicine and of health research and policy and director of the Stanford Prevention Research Center, adjunct professor at Harvard School of Public Health and Imperial College London.   http://now.tufts.edu/articles/man-who-did-math

(3a3) Prasad V et al., Reversals of Established Medical Practices:  Evidence to Abandon Ship   JAMA. 2012;307(1):37-38. doi:10.1001/jama.2011.1960.  at http://jama.jamanetwork.com/article.aspx?articleid=1104821   One of the authors of this article was Ioannidis (see (3a2) above)

(3a4) Researchers Identify 146 Contemporary Medical Practices Offering No Net Benefits,  in Mayo Clinics Proceedings,  Volume 88, Issue 8 (August 2013), published by Elsevier at http://www.elsevier.com/about/press-releases/research-and-journals/researchers-identify-146-contemporary-medical-practices-offering-no-net-benefits

For ease of referral to the sources indicated here, if there is no highlighted link, you can (a) use your cursor to drag over and select a URL from the footnote (select the letters beginning with www or http and ending just before the next space; be sure to select all of that but no more, not even a space), then (b) control - c  (to copy that); then (c) paste that (control - v) into the horizontal web-address slot at the top left of your browser page, then press ENTER on your keyboard.

(3a5)  Ioannidis JPA (2005) Why Most Published Research Findings Are False.  PLoS Med 2(8): e124. doi:10.1371/journal.pmed.0020124

(3b) Gary J. Myers et al., Postnatal Exposure to Methyl Mercury from Fish Consumption: a Review and New Data from the Seychelles Child Development Study, Neurotoxicology. 2009 May; 30(3): 338–349. Published online 2009 January 21. doi:  10.1016/j.neuro.2009.01.005  PMCID: PMC2743883  NIHMSID: NIHMS119840  at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2743883/   Summarized in Table 2 of this study were other studies showing associations with postnatal exposure to mercury:  Grandjean et al (1999a and b) -- adverse associations at 7-12 years; Davidson et al.,1998, improvements according to 2 tests at age 5.5, but decrements in one test as exposure increases; Axtell et al,  2000, scores at 5.5 years improving or worsening at lower or higher exposures, respectively (10 ppm dividing line); Huang et al, 2003, at 5.5 years a beneficial association.  Weihe et al.,(http://www.ncbi.nlm.nih.gov/pubmed/12002946) found subtle neurobehavioral deficits linked to mercury exposure at ages 7-12.

(3b0) EPA-823-R-01-001  January 2001  Water Quality Criterion for the Protection of Human Health: Methylmercury at http://water.epa.gov/scitech/swguidance/standards/criteria/aqlife/methylmercury/upload/2009_01_15_criteria_methylmercury_mercury-criterion.pdf

(3b1)  P. Grandjean et al., Human Milk as a Source of Methylmercury Exposure in Infants,  Environmental Health Perspectives, accepted Oct. 1993   http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1567218/pdf/envhper00389-0074.pdf

(3b2) Myers et al, Postnatal Exposure to Methyl Mercury from Fish Consumption: a Review and New Data from the Seychelles Child Development Study in Neurotoxicology (of NIH) at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2743883/#!po=2.27273.     In the Seychelles, the exclusive breastfeeding rate for six months was only 1.5% in 2008 (1/8 of the 2008 U.S rate), rising to 2% in 2010. (Report on the Situation of Infant and Young Child Feeding in Seychelles, August 2011, IBFAN, The Committee on the Rights of the Child   www.ibfan.org/art/IBFAN_CRC58%20-2011_Seychelles.pdf  

For ease of referral to the sources indicated here, if there is no highlighted link, you can (a) use your cursor to drag over and select a URL from the footnote (select the letters beginning with www or http and ending just before the next space; be sure to select all of that but no more, not even a space), then (b) control - c  (to copy that); then (c) paste that (control - v) into the horizontal web-address slot at the top left of your browser page, then press ENTER on your keyboard.

(3b3)  R M Pitkin et al., Mercury in human maternal and cord blood, placenta, and milk.Proceedings of The Society for Experimental Biology and Medicine 04/1976; 151(3):565-7. DOI:10.3181/00379727-151-39259  Source: PubMed at

http://www.researchgate.net/publication/21898959_Mercury_in_human_maternal_and_cord_blood_placenta_and_milk and  Food Additives & Contaminants: Part B: Surveillance  Volume 5, Issue 1, 2012  Robert W. Dabeka et al., Survey of total mercury in infant formulae and oral electrolytes sold in Canada  DOI: 10.1080/19393210.2012.658087  at http://www.tandfonline.com/doi/full/10.1080/19393210.2012.658087#tabModule

(3c)  Jens Walkowiak et al., Environmental exposure to polychlorinated biphenyls and quality of the home environment:  effects on psychodevelopment in early childhood.  Lancet 2001: 358: 1602-07  Abstract at http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(01)06654-5/abstract

(3d) "About Allergies/ Why Are Allergies Increasing?" found at  http://fooddrugallergy.ucla.edu/body.cfm?id=40

(3d1) Bernard Weiss, Silent Latency Periods in Methylmercury Poisoning and in Neurodegenerative Disease, Environmental Health Perspectives • Volume 110 | Supplement 5 | October 2002 at  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1241259/pdf/ehp110s-000851.pdf  

Very much the same message is presented in Giordano et al., Review Article, Developmental Neurotoxicity: Some Old and New Issues, International Scholarly Research Network, ISRN Toxicology Volume 2012, Article ID 814795, doi:10.5402/2012/814795 at http://www.hindawi.com/isrn/toxicology/2012/814795/ref/

(3e) Rice DC, Evidence for delayed neurotoxicity produced by methylmercury. Neurotoxicology [1996, 17(3-4):583-596] (PMID:9086479) Toxicology Research Division, Bureau of Chemical Safety, Health Canada.

(3f)  Rice et al., Critical Periods of Vulnerability for the Developing Nervous System: Evidence from Humans and Animal Models, p. 525  at  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1637807/pdf/envhper00312-0143.pdf

(3g) Evenhouse et al., Improved Estimates of the Benefits of Breastfeeding Using Sibling Comparisons to Reduce Selection Bias,  Health Serv Res. 2005 Dec; 40(6 Pt 1): 1781–1802. PMCID: PMC1361236, at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1361236/

(3h) Autism rates associated with nutrition and the WIC program, Shamberger R.J., Phd, FACN, King James Medical Laboratory, Cleveland, OH  J Am Coll Nutr. 2011 Oct;30(5):348-53.  Abstract at www.ncbi.nlm.nih.gov/pubmed/22081621  The full text, including the quoted passages, can be purchased for $7 or reference librarians at local libraries could probably obtain it at no charge. 

3k) (U.S. EPA: The Effects of Great Lakes Contaminants on Human Health, last paragraph of Section IV, at http://www.epa.gov/greatlakes/health/report.htm)

3m) Colen et al., Is breast truly best? Estimating the effects of breastfeeding on long-term child health and wellbeing in the United States using sibling comparisons, Soc Sci Med. 2014 May;109:55-65. doi: 10.1016/j.socscimed.2014.01.027. Epub 2014 Jan 29. at http://www.ncbi.nlm.nih.gov/pubmed/24698713

(4) Dissemination and publication of research findings: an updated review of related biases, F Song et al., Health Technol Assess 2010;14(8):1–220.  Also Publication bias and clinical trials, K. Dickersin, Controlled Clinical Trials, Volume 8, Issue 4, December 1987, Pages 343–353  Elsevier  Also, although the quality of its articles is very uneven, Wikipedia has a good article on "publication bias."

For ease of referral to the sources indicated here, if there is no highlighted link, you can (a) use your cursor to drag over and select a URL from the footnote (select the letters beginning with www or http and ending just before the next space; be sure to select all of that but no more, not even a space), then (b) control - c  (to copy that); then (c) paste that (control - v) into the horizontal web-address slot at the top left of your browser page, then press ENTER on your keyboard.

(4a)  Agency for Healthcare Research and Quality, U.S. Department of Health and Human Services, "Systems to Rate the Strength of Scientific Evidence, Evidence Report/Technology Assessment: Number 47" at  http://archive.ahrq.gov/clinic/epcsums/strengthsum.pdf

(4b)  For a good summary of many types of reporting bias, see Table 2 of "AHRQ Series Paper 5: Grading the strength of a body of evidence when comparing medical interventions."

https://effectivehealthcare.ahrq.gov/ehc/products/457/1752/methods-guidance-grading-evidence-131118.pdf

(4c1) CDC's Health United States 2008, Table 75, and Data Table for Figure 7.

(4c2) Poor Neighborhoods Home to More Obese Kids: Study   Researchers find link between weight and the economic and educational status of the community   HealthDay News, Nov., 2012  at  http://consumer.healthday.com/public-health-information-30/demographics-news-173/poor-neighborhoods-home-to-more-obese-kids-study-670620.html ; also Dana Hughes, DrPH, Mary Kreger, DrPH, et al.: Reducing Health Disparities Among Children:  Strategies And Programs For Health Plans. At http://nihcm.org/pdf/HealthDisparitiesFinal.pdf;

(4d)  Effects of Promoting Longer-term and Exclusive Breastfeeding on Adiposity and Insulin-like Growth Factor-I at Age 11.5 Years  :  A Randomized Trial.   Richard M. Martin, PhD et al.  JAMA. (Journal of the American Medical Assn.) 2013;309(10):1005-1013. doi:10.1001/jama.2013.167. March 13, 2013, Vol 309, No. 10  Found at http://jama.jamanetwork.com/article.aspx?articleid=1667089

(4e)  Kwok MK, et al., Does breastfeeding protect against childhood overweight?  Int J Epidemiol. 2010;39(1):297-305  found at http://ije.oxfordjournals.org/content/39/1/297.full.pdf

(4f)  Brion MJ  et al.  What are the causal effects of breastfeeding on IQ, obesity and blood pressure?  Int J Epidemiol. 2011;40(3):670-680  found at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC314707

(4g)  Michels KB, et al, A longitudinal study of infant feeding and obesity throughout life course. Int J Obes (Lond). 2007 Jul;31(7):1078-85. Epub 2007 Apr  http://www.ncbi.nlm.nih.gov/pubmed/17452993

(4h) Nelson MC et al., Are adolescents who were breast-fed less likely to be overweight?:  Analyses of sibling pairs to reduce confounding , Table 3  Epidemiology. 2005;16(2):247-253 found at http://journals.lww.com/epidem/Fulltext/2005/03000/Are_Adolescents_Who_Were_Breast_fed_Less_Likely_to.15.aspx

 (5)   S Patandin et al.,  Effects Of Environmental Exposure To  Polychlorinated Biphenyls And Dioxins On Growth And Development In Young Children:  A Prospective Follow-Up Study Of Breast-Fed And Formula-Fed Infants From Birth Until 42 Months Of Age    at   http://Repub.Eur.Nl/Res/Pub/19721 , p. 68

 (6)  U.S. ATSDR    Public Health Statement for Polychlorinated Biphenyls (PCBs),  November 2000, Balfanz et al. 1993; MacLeod 1981; Wallace et al. 1996,  p. 569

For ease of referral to the sources indicated here, if there is no highlighted link, you can (a) use your cursor to drag over and select a URL from the footnote (select the letters beginning with www or http and ending just before the next space; be sure to select all of that but no more, not even a space), then (b) control - c  (to copy that); then (c) paste that (control - v) into the horizontal web-address slot at the top left of your browser page, then press ENTER on your keyboard.

(7)  Banaschewski et al., Autism and ADHD across the life span. Differential diagnoses or comorbidity?  Nervenarzt. 2011 May;82(5):573-80. doi: 10.1007/s00115-010-3239-6. [Article in German] at www.ncbi.nlm.nih.gov/pubmed/21484168          Also see Murray,  Attention-deficit/Hyperactivity Disorder in the context of Autism spectrum disorders. Curr Psychiatry Rep. 2010 Oct;12(5):382-8. doi: 10.1007/s11920-010-0145-3  at http://www.ncbi.nlm.nih.gov/pubmed/20694583

(7a) Jusko et al.,  Prenatal and Postnatal Serum PCB Concentrations and Cochlear Function in Children at 45 Months of Age, Environmental Health Perspectives, 22 July 2014 (Advance Pub.) at http://ehp.niehs.nih.gov/wp-content/uploads/advpub/2014/7/ehp.1307473.pdf

(7b) dB: What is a decibel? at  http://www.animations.physics.unsw.edu.au/jw/dB.htm

(7c)   -  see Section 1.a of www.breastfeeding-toxins.info

 (8) P. Grandjean et al., Human Milk as a Source of Methylmercury Exposure in Infants,  Environmental Health Perspectives, accepted Oct. 1993   http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1567218/pdf

Marques RC, et al., Hair mercury in breast-fed infants exposed to thimerosal-preserved vaccines. Eur J Pediatr. 2007 Sep;166(9):935-41. Epub 2007 Jan 20 

 U.S. ATSDR document on mercury at http://www.atsdr.cdc.gov/toxprofiles/tp46-c5.pdf, p. 443, showing estimate of 8 ppb.

Code of Federal Regulations, Title 21, Chapter 1, Subchapter B, Part 165, Subpart B, Sec. 165-110 at http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfCFR/CFRSearch.cfm?fr=165.110, showing maximum allowed of 2 ppb

(8a) Lorber et al.,  Infant Exposure to Dioxin-like Compounds in Breast Milk, Volume 110 | Number 6 | June 2002 • Environmental Health Perspectives (a peer-reviewed journal published by the National Institute of Environmental Health Sciences of NIH)  http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=54708#Download

(8b) Mocarelli et al., Perinatal Exposure to Low Doses of Dioxin Can Permanently Impair Human Semen Quality, Environ Health Perspect. May 2011; 119(5): 713–718. Published online Jan 24, 2011. doi:  10.1289/ehp.1002134  at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3094426/

(9) Auyeung et al., Prenatal and postnatal hormone effects on the human brain and cognition, Pflugers Arch - Eur J Physiol, 2013, at http://docs.autismresearchcentre.com/papers/2013_Auyeung_Prenatal%20and%20postnatal%20hormone%20effects_EuJPhysio.pdf  These authors cite five other studies in support of their generalization that experiments with a wide range of mammals “consistently” demonstrate the importance of testosterone to development of the brain.

For ease of referral to the sources indicated here, if there is no highlighted link, you can (a) use your cursor to drag over and select a URL from the footnote (select the letters beginning with www or http and ending just before the next space; be sure to select all of that but no more, not even a space), then (b) control - c  (to copy that); then (c) paste that (control - v) into the horizontal web-address slot at the top left of your browser page, then press ENTER on your keyboard.

(9a) Lackmann, Human Milk, Environmental Toxins and Pollution of Our Infants: Disturbing Findings during the First Six Months of Life,  Int J Biomed Sci. Jun 2006; 2(2): 178–183, at www.ncbi.nlm.nih.gov/pmc/articles/PMC3614598.   The “13 times as high” was taken from data quoted in “Results” for the sum of 3 PCB congeners, difference at six months.

Also Kommission “Human-Biomonitoring” des Umweltbundesamtes:  Stoffmonographie PCB - Referenzwerte für Blut   (Commission on Human Bio-Monitoring of the (German) Federal Environmental Office:  Substance Monograph on PCB - - Reference Values for Blood)  At http://www.umweltdaten.de/gesundheit/monitor/pcbblut.pdf , Section 8.3. found within http://www.umweltbundesamt.de/gesundheit/publikationen/index.htm , website of Umwelt Bundes Amt (German Federal Environmental Office).

Also Infant Exposure to Dioxin-like Compounds in Breast Milk, Lorber and Phillips  Volume 110 | Number 6 | June 2002 • Environmental Health Perspectives    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1240886/pdf/ehp0110-a00325.pdf

(10) Schell et al., Organochlorines, lead, and mercury in Akwesasne Mohawk youth,  Environ Health Perspect. Jun 2003; 111(7): 954–961.  at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1241531/pdf/ehp0111-000954.pdf

(11) U.S. CDC web page at http://www.cdc.gov/ART/

*As the author of the above, my role has not been to carry out original research, but instead it has been to read through very large amounts of scientific research that has already been completed on the subjects of environmental toxins and infant development, and then to summarize the relevant findings; my aim has been to put this information into a form that enables readers to make better-informed decisions related to these matters.  The original research articles and government reports on this subject (my sources) are extremely numerous, often very lengthy, and usually written in a form and stored in locations such that the general public is normally unable to learn from them. 

My main qualification for writing these publications is ability to find and pull together large amounts of scientific evidence from authoritative sources and to condense the most significant parts into a form that is reasonably understandable to the general public, while maintaining accuracy in what is said.  My educational background included challenging courses in biology and chemistry in which I did very well, but at least as important has been an ability to correctly summarize in plain English large amounts of scientific material.  I scored in the top one percent in standardized tests in high school, graduated cum laude from Oberlin College, and stood in the top third of my class at Harvard Business School.  

There were important aspects of the business school case-study method that have been helpful in making my work more useful than much or most of what has been written on this subject, as follows:   After carefully studying large amounts of printed matter on a subject, one is expected to come up with well-considered recommendations that can be defended against criticisms from all directions.  The expected criticisms ingrain the habits of (a) maintaining accuracy in what one says, and (b) not making recommendations unless one can support them with good evidence and logical reasoning.  Established policies receive little respect if they can’t be well supported as part of a free give-and-take of conflicting evidence and reasoning.  That approach is especially relevant to the position statements on breastfeeding of the American Academy of Pediatrics and the American Academy of Family Physicians, which statements cite only evidence that has been

   (a) selected, while in no way acknowledging the considerable contrary evidence⁽¹⁾ and

(b) of a kind that has been authoritatively determined to be of low quality; former U.S. Surgeon General Regina Benjamin acknowledged that essentially all of the research supporting benefits of breastfeeding consists merely of observational studies.^(1a)  One determination that evidence from observational studies is of low quality has been provided by Dr. Gordon Guyatt and 14 of his associates;⁽²⁾ Dr. Guyatt is chief editor of the American Medical Association’s Manual for Evidence-based Clinical Practice, in which 26 pages are devoted to examples of studies (most of which were observational) that were later refuted by high-quality studies.^(2a)  A similar assessment of the low quality of evidence from observational studies has been provided by the other chief authority on medical evidence (Dr. David Sackett),^(2c) writing about “the disastrous inadequacy of lesser evidence,” in reference to findings from observational studies.^(2b)

When a brief summary of material that conflicts with their breastfeeding positions is repeatedly presented to the physicians’ associations, along with a question or two about the basis for their breastfeeding recommendations, those associations never respond.  That says a lot about how well their positions on breastfeeding can stand up to scrutiny.

The credibility of the contents of the above article is based on the authoritative sources that are referred to in the footnotes: The sources are mainly U.S. government health-related agencies and reputable academic researchers (typically highly-published authors) writing in peer-reviewed journals; those sources are essentially always referred to in footnotes that follow anything that is said in the text that is not common knowledge.  In most cases a link is provided that allows easy referral to the original source(s) of the information.  If there is not a working link, you can normally use your cursor to select a non-working link or the title of the document, then copy it (control - c usually does that), then “paste” it (control - v) into an open slot at the top of your browser, for taking you to the website where the original, authoritative source of the information can be found.  

The reader is strongly encouraged to check the source(s) regarding anything he or she reads here that seems to be questionable, and to notify me of anything said in the text that does not seem to accurately represent what was said by the original source.  Write to dm@pollutionaction.org.  I will quickly correct anything found to be inaccurate.

For a more complete statement about the author and Pollution Action, please go to www.pollutionaction.org. 

Don Meulenberg

Fredericksburg, VA, USA