“Is Breast Really Best?” The Debate Doesn’t End Here…

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breastfeeding rocksA couple weeks ago I came across an academic article[1] stating that the benefits of breastfeeding were overstated using discordant sibling data from a national survey to ‘prove’ the point.  Now, this hadn’t hit the news yet, I took some time to digest the findings and the limitations and figured I’d have time to write it up slowly.  Ha!  Yesterday the proverbial shit hit the fan and news sites were sharing articles claiming things like the benefits of breastmilk are overrated or that breastmilk is “no better” for a baby than formula.  As I cringed over the interpretation, I figured it was time to throw my hat in after all…

What does the research say? (And, is it good research?)

The research used data from the children of the 1979 cohort of the National Longitudinal Survey of Youth which means the questions are standardized, but they reach a large number of kids which is great for researchers.  They analyzed over 8000 children, just under 1800 of which were what was termed ‘discordant’ sibling pairs, meaning that one of them was “breastfed” while the other was strictly formula-fed.  The authors then looked at the outcomes as assessed between 4 and 14 years of age on 11 specific outcomes: Three health outcomes (BMI, obesity, and asthma), three behavioural outcomes (hyperactivity, parental attachment, and behavioural compliance), and five academic achievement outcomes (Peabody Vocabulary Test, Peabody Reading Recognition, Peabody Math Ability, Weschler Intelligence Scale, and ‘scholastic competence’).  Notably, BMI, obesity, and the standardized achievement outcomes (everything except ‘scholastic competence’) were objectively measured, asthma and the behavioural outcomes were maternal report, and scholastic competence was child report and consisted six questions to assess the child’s sense of self-competence in school.

They ran separate models for the entire sample and the sibling only samples.  They also ran between-family estimates and within-family estimates, and for all models the usual covariates were included.  In short, the statistics are sound.  For the between-family estimates, there was a significant effect of breastfeeding on all of the variables and this remained when looking at sibling samples only.  However, when the within-family estimates were used, these results all but disappeared (with the exception of behavioural compliance which was weakened but still trending significance).  Within-family estimates are different in that they include the family as a variable meaning that any unobserved, but stable influence of the family is included.  These results held for breastfeeding ever (a yes/no dichotomy) and breastfeeding duration (in weeks).  Interestingly, the authors enjoy speaking about the null findings in the direction against breastfeeding as being meaningful and worthy of discussion (i.e., mother reported asthma) while stating that the null findings in the direction for breastfeeding are simply that: null.

So how good is the research?  Well, we’ll get into what’s missing next, but the first sign of something being off is where this is published.  A huge study, if it was conducted well, statistically robust, and had the right measurement of variables would be in something like the New England Journal of Medicine or Pediatrics (though there have been some real doozies in that one recently when trying to publish more social sciences instead of medicine) or Science or Nature.  It’s not.  It’s not in a bad journal by any means, but it raises the question of what area was limited that these other journals would have turned it down (because it only makes sense to try and go to one of the big ones first if you have groundbreaking data).  With that, let’s look at…

What is the research missing?

There are enough important variables missing that I can see why it wasn’t in a better journal.  First and foremost, the definition of breastfeeding is hardly informative.  The yes/no measure is almost useless as it would include mothers who breastfed once which we know is not indicative of any benefits, especially when looking long-term.  But even the duration in weeks (weeks!) is misleading because it doesn’t deal with the difference between exclusive and mixed breastfeeding.  Anyone who looks at the data on health and other benefits of breastfeeding is well aware that the strongest influences are for long-term, exclusive breastfeeding (which also happens to be the biological and historical normal).  The authors also fail to include what the average duration was so we have no idea if we’re looking at 3 weeks, 20 weeks, 5 weeks, etc. and the number of families at the higher ends.  If no families breastfed for any significantly long duration, there would be no way to find the proper relationships because you have range restriction on the key variable of interest.

Second, there is no information on the influence of these within-family effects, not even the actual weights in the regression equations.  That is, we have no idea why one child was breastfed but another not, what birth order it was, or what the interactions were with these influences.  We don’t know if the discordant siblings were mixed-fed and formula-fed which might have very different implications than exclusively-breastfed versus formula-fed.  Without this information, we’re missing the crucial part of the picture.  Notably, looking at the mean data they do provide, the discordant sibling sample had a much lower SES than those who did not have discordant siblings (i.e., the siblings were both either breastfed or not breastfed).  Discordant siblings were also more likely to have a child that was preterm, and was also less likely to have drank during pregnancy.  We just don’t know how these variables interact with breastfeeding which seems a crucial distinction.

Third, it’s missing a lot of child health outcomes relevant to the breastfeeding discussion.  I realize they were limited in outcome selection because it was based on national data, but the outcomes selected are not a lot of the standard ones associated with long-term breastfeeding outcomes which predominantly focus on health.  The WHO’s recent meta-analysis on the same topic[2] looked at cholesterol, blood pressure, obesity, type-2 diabetes, and intelligence, finding a tiny effect of breastfeeding duration on obesity (which was one of the measures here) and a small effect on intelligence (using some of the same measures included in this review).  The other three health outcomes – which included significant effects of breastfeeding on blood pressure and type-2 diabetes – were not included here.  Of course no other health outcomes, like cancer, were included which adds to this limitation.  In short, concluding that the benefits of breastfeeding are overstated or non-existent when only looking at a small subset of outcomes is a little disingenuous.

Fourth, the data is entirely missing the outcomes for mothers.  The rates of cancer for mothers is significantly lower long-term for women who breastfeed versus those who do not[3].  Even if there truly were no differences between breastfeeding and formula for babies (which is not the case, as you’ll see if you read the next paragraph), it would still benefit everyone for mothers to breastfeed as the alternative puts them at higher risk of dying.  According to recent research, the United States are losing 72,000 women prematurely because of a failure to reach “optimal breastfeeding rates” (defined as 90% of women breastfeeding exclusively for 6 months)[4].  Does that not matter?

Finally, and perhaps most importantly for the idiotic headlines we’re seeing, the data here speaks to long-term outcomes with no discussion or consideration of the immediate or short-term outcomes which strongly favour breastfeeding.  The authors of this report seem to just ignore that evidence in favour of focusing all discussion exclusively on long-term outcomes.  In the US alone, the immediate (< 1 year) cost of not reaching “optimal breastfeeding rates” is resulting in 911 deaths per year (almost all infants under 1 year) and a cost to the health care system of $13 billion a year[5].  I dare anyone to read that and suggest that breastfeeding is “no better” than formula.

What is the take-home message?

First I have to give credit to the authors for a section of their paper that has received almost zero attention: At the end they argue that instead of focusing our efforts on simply harassing women to breastfeed, we need to change the structure of our society.  That if we want to see improvements in long-term outcomes, we have to focus on the between-family differences by providing maternity leave, better health care, and a host of things relating to poverty or SES.   Myself, I think that we should also start looking at other possibilities for the within-family differences, such as style of parenting, which often remains similar across children (though definitely not always).  I do, however, laud their efforts to highlight problems in the current system instead of just focusing on the idea that formula is just as good, though sadly the media has ignored this part in favour of the “just use formula” aspect of the research.

Based on the research though, I think we can conclude that there are outcomes in which breastfeeding will not have an influence.  I have no idea if all of these outcomes here will fit this bill without knowing more about the duration and exclusivity of breastfeeding in this sample (though notably many of these outcomes have already been found to be low on the breastfeeding-effects totem pole so it’s not too surprising there weren’t significant differences here).  The idea that one can say breastfeeding is no better than formula or that the benefits are exaggerated is not supported by this data.  I do like, however, the use of discordant siblings and hope to see more of that research going forward as it may provide us with valuable information.

What the research does support is the idea that breastfeeding is not a magical elixir that will fix everything forever more.  Sadly I know there are people that treat it this way and it’s a problem as any evidence like this is then held up as proof that breastfeeding isn’t a panacea.  Breastfeeding is wonderful, natural, and in some areas of the world, it absolutely is the difference between life and death.  In our Western world, however, to assume breastfeeding has such long-term impacts that it would outweigh years of experiences ignores not only the wealth of other factors that influence these outcomes, but common sense.  Most people are aware of this and don’t try to make breastfeeding out to be more than it is.  It’s just that what it is, is still pretty darn cool.

Take the measures of intelligence, for example.  These authors and many others look at Western constructs of intelligence – namely verbal and mathematical IQ assessed using standardized tests – and although these are valuable, they are largely influenced by education and exposure to certain problems and bits of information and do not reflect unlearned intelligence.  As such, SES, education views in the household, school systems, parental support on homework and studying, etc. are all going to influence this far more than breastfeeding.  Even looking at health outcomes, how could one expect breastfeeding in infancy (especially short-term breastfeeding or mixed feeding that is predominantly formula) to overcome a steady diet of processed, non-nutritious foods for years after?  Now, if all of this were taken into account, might we see a difference then?  I don’t know, but I think it would be much more likely than when we don’t consider the other influences at all.

When we look at this research in conjunction with the wealth of other findings out there, we can see that the long-term effects of breastfeeding are small and perhaps even negligible for certain families where other factors are far more influential.  However, even if we took this data at face value and said it was the perfect study, why-oh-why would we only consider long-term outcomes in the assessment of feeding methods for infants in making statements about the overall efficacy of breastfeeding?  Since when did we not care at all about short-term consequences, especially when they include death that is significant at a population level?  Since when did we not care about the outcomes for mothers?  Or does our society only want to care about our influence on the economy, meaning they need to get us back to work and away from our kids as quickly as possible, even if it kills us sooner?

This study far from “proves” anything.  The journalists that have reported on it have once again taken liberties in their reporting that fall squarely on the side of irresponsible (however the authors themselves need to take some blame too here for blatantly ignoring a wealth of research that speaks to the “benefits” of breastfeeding short-term and for mothers, and for not speaking of their own limitations in this regard in their piece).  If you thought breastfeeding was so magical it would overcome anything, then this study should hopefully show you that no it’s not.  If you have a more realistic view of breastfeeding, I’m not sure this adds much to the discussion as you already know breastfeeding does provide things formula does not, but that in our society women use formula for many reasons.

My biggest fear with articles like that is that it completely detracts from the push to make breastfeeding easier for those who want to do it (i.e., those fighting for greater support and leave and all the other things necessary for many women to have a healthy, happy breastfeeding relationship) and to make breast milk more readily available for women who don’t want to turn to formula but cannot breastfeed for whatever reason.  I can only hope that flawed science doesn’t take us down a rabbit hole we have to dig our way out of yet again…



[1] Colen CG, Ramey DM.  Is breast truly best? Estimating the effects of breastfeeding on long-term child health and well-being in the United States using sibling comparisons.  Social Science & Medicine 2014. (Ahead of print)

[3] For a review with all the references, see: http://evolutionaryparenting.com/two-bs-and-the-big-c/

[4] Bartick M, Stuebe A, Schwarz EB, Luongo C, Reinhold AG, Foster EM.  Cost analysis of maternal disease associated with suboptimal breastfeeding.  Obstetrics & Gynecology 2013; 122: 111-9.

[5] Bartick M, Reinhold A.  The burden of suboptimal breastfeeding in the United States: a pediatric cost analysis.  Pediatrics 2010; 125: e1048-e1056.

Comments

  1. Amanda Ellithorpe says

    Thank you so much for writing this piece! After seeing the other two floating around Facebook yesterday, I was enraged, to say the least. When I woke up today to see the article about the new study from Brown University, I felt vindicated and relieved that there was good research from a good source out there on bf. Then I came across your piece tonight and feel much better. I feel equipped to go into battle, if necessary!

    • Emma says

      Do you have a link to the article you mentioned from Brown University, or the reference please? Have done a quick search but can’t find anything and would be interested to read it.

      And thank you so much Tracy, I’m nursing 21 month old twins and am fully expecting to receive a newspaper clipping of the breast is not best news report in the post from my MIL. Your critique will be invaluable in helping me to counter some of her arguements to stop BF. Furthermore, I volunteer as a breastfeeding peer supporter and the damage that the news reports have already done is startling!

  2. Amy says

    “Finally, and perhaps most importantly for the idiotic headlines we’re seeing, the data here speaks to long-term outcomes with no discussion or consideration of the immediate or short-term outcomes which strongly favour breastfeeding. The authors of this report seem to just ignore that evidence in favour of talking exclusively about the previous research on long-term outcomes. In the US alone, the immediate (< 1 year) cost of not reaching “optimal breastfeeding rates” is resulting in 911 deaths per year (almost all infants under 1 year) and a cost to the health care system of $13 billion a year[5]. "

    In reference to the above quote, I went to that source and all I saw was how much it costs the US if breast feeding could fix/ameliorate all of those childhood diseases. I did not see any evidence that it actually does. Do you have any links to studies showing that it actually stops all of the things listed in that source?

    I am looking for more information, and not in any way trying to be obtuse or argumentative. I nursed both my sons for a year without supplementing, but I'm pregnant with my third now and interested in supplementing. I'm just trying to learn as much as I can. Thanks for any links you can give me.

    • says

      Hi Amy,

      If you check out the article there, they cite all the sources at the start for how they have shown breastfeeding reduces the rates of those diseases. It’s not actually fixing all of them, but reducing the rates.

      Does that help?

      Tracy

      p.s. You have to read more than the abstract, but rather the introduction for the background research as to why these outcomes were chosen.

      • Amy says

        The study seemed to site a 2007 AHRQ report as to why it choose those diseases to put monetary value to. I went to that report and this was the conclusion.

        “Conclusions: A history of breastfeeding is associated with a reduced risk of many diseases in infants and mothers from developed countries. Because almost all the data in this review were gathered from observational studies, one should not infer causality based on these findings. Also, there is a wide range of quality of the body of evidence across different health outcomes.”

        So, I’m still looking for information on the importance of breast feeding on short term outcomes. As you said in this article, the evidence on long term outcomes is not completely shown either.

        Any thoughts? Am I missing something?

        • says

          So the conclusion you read is a standard in Western societies. ALL studies are observational – we can’t run random controlled trials here – it’s simply impossible. To do a non-observational study would involve randomly assigning women to breastfeed or not which of course is highly unethical. The range of quality is normal in studies – most of what I’ve read in terms of WHO reports focus on high-quality studies and report the short-term outcomes as beneficial.

          Basically, you will NEVER see a “high-quality” study looking at breastfeeding because high quality (i.e., non-observational) = randomized control trials which are unethical for things like breastfeeding. BUT because of that, every review, every meta-analysis will list this as a limitation in their research. They have to. In fact, if they don’t, they aren’t being ethical :)

  3. kate says

    while i’m pro breastfeeding and have breast fed (and still am) both of my children i didn’t take issue with the article. while one might feel pushing breast is best is great for all of those question what they would like to do it’s hurting all those mothers challenged to keep up with their childs demands. i shared the stated article about breast milk being overrated with my mom group because many of them struggled. one breast fed their child for 3 months nothing – they gave formula after each half hour feed but literally nothing came out.
    i think we all need to step back and let each mother make the choice for themselves. no one should be made to feel bad for feeding their baby, weather it be by breast or bottle

    • says

      There is a large difference between not making people feel bad and sharing bad science or unfounded conclusions. I think people deserve to know that there are differences and to make their decisions for their families based on that or fight for change. When we sweep it under the rug, we do no one any favours. But that’s just my opinion.

  4. says

    Thanks Tracy for your well written response to this study. Especially the last paragraph is of great concern to me. Here in the Netherlands lots of people jubilantly shared the headlines, yet no one seemed bothered to look at the limitations of this study. What happens next is that breastfeeding mothers who are struggling are left out in the cold yet again. They are systematically categorised as *insert some horrible word referring to some violent group or ideology* but hands-on, practical help is still further away than ever.
    I have one small thing to add: I’m wondering if the researchers took into account that in the seventies and eighties feeding on demand wasn’t common practice. Most people who breastfed in those days were told to keep strict schedules and leave a long time between the feedings. I also wonder if one sibling was bottle fed, if that had an effect on the feeding on demand of the other sibling? Is it not very likely that within a family a bottle feeding culture exists and that the breastfeeding itself was far from optimal? I would love to hear your thoughts on that.

    • says

      I had thought about the breastfeeding practices at those times except it’s hard as the final data collection was 2010 so the kids were actually fed in the 90s and 2000s where things were a little different :) The 1979 cohort is the parental cohort.

      However, it’s a great point about the on-demand feeding if one is bottlefed. This is one of the reasons I would have liked to see more information about the siblings – did they bf first then bottle feed or the other way around? This all would influence the habits.

  5. Dana says

    From my experiences learning about nutrition and weight loss I know that people will conduct poorly-constructed studies and then try to pass them off as good science to an unquestioning mainstream media. Even when they get good data, they misinterpret it, either accidentally or deliberately. (See also the China Study, a brazen example of this.) So just because some group comes out with “research” doesn’t mean it’s worth anything.

    No matter what they say, breast is best, especially from a well-nourished mother.

    This is a no-brainer. Humans have been around in some form or fashion for at least a million years. For most of that million years, we didn’t have formula. We are still here. There’s your sign.

    Formula is simply this: “You can’t or won’t nurse your infant but at least you are still feeding them.” That’s it, that’s all, nothing else.

    • breathe16 says

      Hi Dana, What’s wrong with the China Study? I know that a personal account here counts for nought, but I gave up meat and dairy and sat/trans fats and am now incredibly healthy (was not as healthy before). About a year into my dietary change I read The China Study and found it very interesting, and was thinking, ‘Aha, some evidence to back what I already know from my own personal experience with food.’ So I am just wondering what the flaws in the study are. Thanks!

  6. says

    As soon as I saw the headline, I anticipated a review of the work here. My immediate suspicions were that the article was sensationalized and either misinterpreted the study or the study was flawed.

    My other thoughts were of the benefits to mothers and the short-term benefits to the infant. I wondered if a formula company funded the research as well. Why are so many people excited to see a headline like that? The many sites that published the article about the study did a tremendous disservice to nursing mouths and their babies.

  7. Jen says

    I appreciate your detailed analysis of the article. I will take issue with your criticisms of the journal it was published in. This was written by a sociologist and most disciplines fairly exclusively publish within their own journals. As this was not someone with a medical degree, they were unlikely to submit to medical journals such as the ones you cited. This is a well respected journal within her field of study and shouldn’t be looked down on because it is not the journal you would expect it to be published in.

    • says

      Except Pediatrics HAS been publishing from people in other disciplines (which has led to it’s own set of problems as they are allowing bad social science in because they don’t know how to review it properly). However, the impact factor of this journal is not very high and clearly did not have the expertise to critically review the paper given what was published.

      • Jen Robinson says

        Which makes me wonder more about the methods, etc. My husband is a public health doc and I’m anxious to have him read the study and give me his assessment on the methods and conclusions. It’s difficult for me to take a study which deals with an intersection of social science and medicine seriously when the author of the study isn’t a scientist/doctor. There is something to be said for interpretation of data based on one’s background. And while the end of the article talks about changing society to help support women in their breastfeeding endeavors, I felt as though this was a throwaway portion because they inferred that women who breastfeed are being martyrs in their desire to be good moms and that this is pointless – kind of a jab at the woman who stays at home with her kids and nurses exclusively for 6 months. I felt that their suggestions about societal change were more of a negative attitude than a positive one.

        The big question that never gets answered is: why do people feel the need to challenge evolutionary biology? We’ve evolved to breastfeed our children and they’ve evolved to be nourished with human milk. Why are we asking if this is the best way to go? We’re not suggesting that other animals shouldn’t nurse their young. It’s the definition of what makes us mammals. People who take offense at the idea that breast is best need to learn to recognize that and divorce the facts from their own personal emotions. Everyone needs to make the choice that is right for his/her own situation but to assert that because one’s situation does not allow one to choose the ideal it is therefore not the ideal is just ridiculous.

        • says

          I would love to hear your husband’s interpretations if he doesn’t mind sharing here too. Like I said, the sibling method is actually quite great in many ways, but their assessment of variables (something psychologists are actually much more concerned about than other disciplines) was rather awful.

  8. Georgia Peach says

    “First I have to give credit to the authors for a section of their paper that has received almost zero attention: At the end they argue that instead of focusing our efforts on simply harassing women to breastfeed, we need to change the structure of our society. ”

    This is not a *section* of their paper, It is the point of their paper. That’s why it’s in a social science journal and not a pediatrics journal. The paper addresses the very real problem that women who are wealthier, better educated, and who have good access to maternity leave, are much more likely to breastfeed. The study acknowledges the fact that breast milk is the best food for infants. That, as you say, is pretty much a settled question.

    Their question is how do we, as a society, improve long term child health outcomes? Their answer is that overemphasizing infant nutrition at the expense of other ways of supporting disadvantaged mothers only further disadvantages them.

    Secondly, since these long term outcomes seem to suggest, though granted in a preliminary way, that children who were formula fed as infants are not significantly worse off than kids who were breast fed as infants, that women should not feel stigmatized for not breastfeeding. Women feel stigmatized for not breast feeding in large part due to be bombarded with messages about the whole-life disadvantages of formula.

    I was not able to breast feed, and I tortured myself about it. I tortured myself because people kept telling me that not only was my infant not getting the best nutrition (which is true), but that he would suffer the consequences of this for the rest of his life.

    I know breast milk is great and all, but as you say, it’s not magic. You may think this is obvious, but it isn’t. What’s really great for kids (in the long run) is having a mother who has the time and support to breast feed. A mother with a partner. A mother making enough money to get by, and a job with maternity benefits. A mother who had the opportunity to get an education.

    I find the study intensely comforting (largely because I think the study is well constructed given its aims). I agree that media coverage has been awful, and has made it look like the study is saying “breast milk is no better than formula”, but it’s not. It’s saying that we are overemphasizing infant nutrition in our strategies to maximize good long term outcomes for kids.

      • Georgia Peach says

        Thanks!

        I think it’s really important that this research be understood, and I am not seeing very good material on it. It seems to me to be divided on “this doesn’t fit with my dogmatically held beliefs so it’s bad science” and “yay! formula is no better than breast milk!”. Neither of these capture the point of the research, and neither is helpful to kids.

        • Julia C. says

          Tracy, great writing. Jen Robinson, you made some great points about evolutionary biology and modern cultural practices. As a mother I have both breast-fed and bottle-fed, so I feel that I know both experiences. I have three sons, and I have to say that among the many benefits of breastfeeding that were overlooked by the study, the most important one, to me, is the incredibly deep, intense physiological connectedness a mother and baby experience while they breastfeed. To me, to miss out on that is truly sad. The exciting but challenging and lengthy experience of pregnancy and the incredible amount of labor involved in the labor ;) culminates in the reward of nursing your baby, in my opinion. It is the most natural continuation of the prenatal nourishment of our babies. We wouldn’t say “Let’s transfer the baby from my uterus to an artificial one because it’s just as good” if we could, would we?
          I so badly want to reach out when I hear a mother saying “Well, my mother couldn’t breastfeed my brother or me, so I’m not even going to bother trying with my baby.” The formula companies themselves have to add a disclaimer to all of their ads to the effect that “Breastfeeding provides the optimal nutrition for babies”. So how can women be so casual about the decision to deny their natural inclination and instincts to nurse their babe and turn to factory-made formula? Because of disinformation. We as moms must support each other AND inform each other. Love to all : )

          • Christie says

            For some moms, breastfeeding is not natural nor instinctual, and can be a great divide between herself and her baby. Everyone’s situation is different.

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