Breastfeeding Medicine

Physicians blogging about breastfeeding

Reports on breastfeeding sibling study are vastly overstated

with 37 comments

A recent analysis of breastfeeding’s effects on child health is making headlines that some of the benefits of breastfeeding have been overstated.

The authors examined behavioral assessments of children born between 1978 and 2006. When they compared breastfed children with formula-fed children, they found that the breastfed kids were healthier and smarter, as many other studies have previously reported. However, they then looked at families in which only some of the children had been breastfed, and they found that whether or not siblings were breastfed did not significantly affect their health outcomes. The authors argue that this proves that a child’s family – not infant feeding – is what really determines long-term child health, and breastfeeding doesn’t really matter.

The biggest problem with this conclusion is that the study ignored anything that happened in these families before their children reached the age of 4, disregarding well-established links between ear infections, pneumonia, vomiting and diarrhea and the amount of human milk a baby receives. There’s strong biological evidence for these relationships, because formula lacks the antibodies and other immune factors in breast milk that block bacteria from binding to the infant gut and airway. For preterm infants, formula exposure raises rates of necrotizing enterocolitis, a devastating and often deadline complication of prematurity. And evidence continues to mount that formula feeding increases risk of Sudden Infant Death Syndrome. Furthermore, mothers who don’t breastfeed face higher rates of breast cancer, ovarian cancer, diabetes, high blood pressure and heart attacks. None of these outcomes were addressed by the recent sibling study. The paper’s authors note they were interested in longer-term outcomes in childhood, but that’s been lost in the news coverage, which has effectively thrown out the breastfeeding mom and baby with the bath water.

There are also other, more subtle issues. The study’s within-family design is a relatively novel attempt to solve an age-old problem. What we really want to know is this: If the same child lived exactly the same life, but in one universe he was formula fed, and in the other, he was breastfed, would it make a difference? In the absence of access to parallel universes, the “gold standard” way to ask this question is to randomly assign study participants to an intervention and see what happens.

The problem is most families would not agree to have a researcher tell them how to feed their infants. Furthermore, it’s unethical to randomly assign people to an exposure if there’s evidence that it is harmful. Researchers have tried to solve this problem by randomizing families to breastfeeding support, but these studies are limited by “crossover” – many families randomized to the control group breastfeed anyway, and many families getting extra support formula-feed. Despite these challenges, the largest trial of breastfeeding support, the PROBIT study, found significant differences in child IQ favoring breastfeeding.

In observational studies – where researchers simply collect data on feeding and outcomes over time – the problem becomes accounting for the differences between families who both decide to breastfeed and succeed vs. those who don’t. In the US, income and education are strongly related to breastfeeding. That’s why the authors of this paper looked within families, where things like income, education, and access to healthy foods were similar. The only thing that differed among siblings was whether they were breastfed or not. Essentially, these siblings were supposed to occupy their own, private, parallel universe—except that they didn’t.

And the assumptions these authors made about these different siblings’ lives are important. For example, in the paper, the authors argue that any differences among siblings would favor the healthier child being breastfed. But, in fact, a preterm sibling of a bottle-fed child might be much more likely to be breastfed, if mom was counseled on the importance of mother’s milk for a NICU baby, than the term sibling of a bottle-fed child. Other issues, such as birth order, age difference between siblings, and changes in parental employment, education and marital status might also affect why a mother breastfed one child and formula fed another. These issues are not explored in any way by this paper, and cannot be “adjusted away,” any more than the differences between families could be adjusted away by prior observational studies. Something was different at the time of that child’s birth that affected the way he or she was fed, destroying the possibility of parallel universes.

But let’s assume, as a thought experiment, that it is the conditions that make breastfeeding possible, and not breastfeeding itself, that reduce child obesity, raise IQs and improve school performance. What does that mean for health policy? If the secret ingredient is “being born in a family where breastfeeding is possible,” then creating the conditions that enable families to breastfeed must be our highest priority. The take-away is that we need to fight for paid parental leave, high-quality childcare and a living wage for every family, regardless of how they decide to feed their infants.

The study’s authors say as much in the conclusion of their paper:

Efforts to increase breastfeeding that solely focus on individually based behavior change without addressing the economic and social realities women face and the difficult tradeoffs they are forced to make in the months following the birth of their child risk alienating and stigmatizing the very women they hope to help. Instead, they need to be considered in conjunction with social policies that also influence a mother’s ability to breastfeed, especially when current recommendations are that women exclusively do so for at least 6 months of age… A truly comprehensive approach to increasing breastfeeding in the U.S., with a particular focus on reducing racial and SES disparities, will need to work toward increasing and improving parental leave policies, flexible work schedules and health benefits even for low-wage workers, and access to high quality child care that can ease the transition back to work for both mother and child.

Feminist scholars have articulating this point eloquently, arguing that breastfeeding is not a “choice” but a reproductive right. If the conditions that allow breastfeeding make our children smarter and healthier, then we’d best stop fighting about how much breastfeeding matters and focus on fighting for the policies and programs that enable all families to optimize the health of their children.

Alison Stuebe, MD, MSc, is a maternal-fetal medicine physician, breastfeeding researcher, and assistant professor of Obstetrics and Gynecology at the University of North Carolina School of Medicine. She is a member of the board of the Academy of Breastfeeding Medicine. You can follow her on Twitter at @astuebe.

Eleanor Bimla Schwarz, MD, MS is a clinician and researcher at the University of Pittsburgh, Departments of Medicine, Epidemiology, and Obstetrics, Gynecology and Reproductive sciences.

Posts on this blog reflect the opinions of individual ABM members, not the organization as a whole.

Written by astuebe

March 1, 2014 at 2:25 pm

37 Responses

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  1. Thank you thank you thank you thank you thank you. You saved me from having to write essentially the same piece, and your M.D.s bring much more credibility to the issue.

    • I agree. And let’s not forget that in bunching together children of women who breastfed in the 1950s with those of women who breastfed in the 1990s we are mixing apples and oranges in demographics; that gestational experience matters greatly to infant outcomes where allergy is concerned; and that reasons for breast-feeding can include the discovery in allergic families that breast-feeding might be protective for a subsequent child. So disadvantaged mothers are muddled with advantaged ones; almost no children over that time frame were solely breastfed as free hospital supplies guaranteed formula exposure for almost all; that birth order and sex and inter birth intervals and maternal diet in infancy and during lactation all influence outcomes, to name just a few concerns when comparing children within families. A whole fruit salad of confounders needs to be picked apart in any properly planned sibling study. Quite apart from the inherent bias towards the null hypothesis of ever versus never breastfeeding studies which fail to rule out the odd colostral feed for babies later formula fed or the odd bovine feed for babies later breastfed!

      Maureen Minchin

      March 1, 2014 at 10:51 pm

  2. You left out one of the most important oversights of the research in your analysis: there was no analysis of what constituted a “breastfed” child. Therefore, if a child took even one feed at the breast, they were put in the breastfeeding group. How long they breastfed and whether they were breastfed exclusively or supplemented with formula was not accounted for. Looking at what we know about how many women initiate breastfeeding but supplement or switch to formula within the first days, weeks, and months, this is a HUGE design flaw. Further, other reliable research has pointed to a dose related effect in multiple factors. Finally, they only looked at factors related to brain developement, obesity, and asthma, which are factors that have shown to be some of the weakest, or at least, most difficult to measure, in terms of the benefits of breastmilk over formula.

    Elisa

    March 1, 2014 at 3:52 pm

    • I was breastfeed exclusively until the age of 3 years old…. I have always had problems in relation to learning & I also have anxiety & suffer from BPD. You are so right about home life being a huge factor in ones general outcome in life.
      My son was formula feeding & now is 13 & honor role student. I have always lived for him . Love & care are the biggest factor to ones overall health.
      Thankyou for being a voice of reason for both sides.

      Sarah

      March 3, 2014 at 1:09 pm

    • This is incorrect. I think you must not have read the study (?). Although it is true that the study does not capture whether children were breastfed exclusively (vs. whether and how much supplementation was used), it absolutely did capture the duration of breastfeeding. They ran two separate analyses, one with breastfeeding treated as a binary variable (so a child that “took even one feed at the breast” was counted as breastfed) but one that used a question about how many weeks old the child was when the mother quit breastfeeding altogether.

      I think the paper is hard to get, so I don’t blame you for not having read it. But I do wonder where you got your information, since I have seen a few criticisms around the web repeating this talking point, which is just flat wrong. It’s almost as though there are a ton of people on the internet who are so devoted to the idea that breastfeeding is superior to formula feeding in every possible way that they are willing to make specious arguments against a paper they haven’t read, if the paper contradicts that idea.

      Unrelated to this particular comment, but related to a major criticism in the OP:
      Since the study authors very particularly chose to focus on discussing the evidence for long-term benefits of breastfeeding, and very particularly chose not to focus on discussing the evidence for short-term benefits thereof, and moreover made this choice explicit in the introduction, I think it is very strange to take the authors to task for not discussing evidence for short-term benefits of breastfeeding. This amounts to criticizing them for not having done a different study entirely. I mean I guess it’s valid if you think a different study would have been more interesting, but it’s not exactly pointing out shortcomings in their data analysis and conclusions, if you see what I mean.

      lame deer

      March 4, 2014 at 7:04 pm

  3. […] Reports on breastfeeding sibling study are vastly overstated […]

  4. What I did like about the other study is not that they disagree with breast feeding health benefits, but that they at least nod at the other factors that go into raising a kid. We focus so strongly on feeding in the beginning that instead of making mothers feel our collective support we make them feel persecuted (on either side). Women defending the breast, women defending the right to bottle feed….you know what is more important? That baby is loved. That baby got fed and is warm. All the breast milk in the world doesn’t fix the damage a terrible home life can create. Bottle nor breast guarantee a good support in life. Which is better? Breast. All the studies point that way. It’s natural. I still have a right to chose bottle for my own reasons. My daughter was bottle, my son is breast.

    Now, I will say this article above is put together far better than the other one was!

    Marilyn Robidoux

    March 1, 2014 at 5:07 pm

    • Hear hear. I sat in pre-natal class with my wife as a bunch of women were given the implicit message that they were not real women or good mothers if they did anything but breast feed. And a lot of these women; young women, bought into that message wholeheartedly. I was appalled.

      Craig Smith

      March 2, 2014 at 3:31 am

    • I wholeheartedly agree. Christina Smiley prefaced a conference on breastfeeding that I went to with these words (I am paraphrasing): What is most important is the mother-child relationship. Breastfeeding alone cannot make a strong infant-maternal bond. This study to some degree (with its flaws) can, I hope, alleviate the stigmatization that some mothers feel about bottle-feeding. I also really loved that the author addressed how important it is that we work towards creating an environment that is more conducive to breastfeeding and mothering an infant, such as longer maternity leave.

      Stephanie Haskins

      March 2, 2014 at 12:10 pm

  5. Could it also be that bottle feeding one sibling, or factors associated with the choice to bottle feed ( such as maternal employment) , have a negative effect on all siblings? For example, if I am bottle feeding die to employment, my breast fed child will also be in day care. Or if my bottle fed child has constant ear infections, I am less available to my breast fed child.

    legoideas

    March 1, 2014 at 5:28 pm

  6. Thank you for this very insightful piece. I always find reports re: breastfeeding interesting as it was not an option for my son, who was internationally adopted from Ethiopia at almost a year old. I have yet to see any reports which include those children and would be curious as to the findings. It amazes me how these babies overcome severe malnutrition, formula being their only option, and grow into such healthy, intelligent, thriving kids. It’s such an extreme turnaround. I’m constantly amazed that my son not only has no illeffects from his start in life, but at almost 4 he is even outperforming what is expected of his age group in intelligence and growth. I, of course, support breastfeeding rights. But I also have a hard time having hard feelings towards formula as it successfully saves the lives of millions of starving children.

    meagantodd2013

    March 1, 2014 at 5:35 pm

  7. Thank you for this insightful piece. I always find breastfeeding research interesting as it was not an option for my son. He was adopted from Ethiopia at almost a year old. I would be interested to see a study which includes these kids in some way as well. I certainly support breastfeeding rights, but I have a very hard time having hard feelings towards formula. It is literally saving the lives of millions and millions of starving babies. And the turnaround is so incredible. Now , at almost 4, my son has not only caught up, but has surpassed what is expected of his age in growth, health, and ability. And all due to formula saving his life. I know many other infant adoptees who have grown into amazing children as well. I am obviously eternally grateful to the nutrition that formula gave my son. I still give to a formula fund in Ethiopia to this day.

    meagantodd2013

    March 1, 2014 at 5:50 pm

    • You might want to rethink your donations to that formula fund, as companies as Nestlé tend to ignore WHO recommendations in developing countries by aggressively marketing their baby foods as a ‘better alternative’ to breastfeeding and distributing samples in hospitals to new mothers. The result for many mothers and babies is a loss of their breastfeeding relationship, all of the family income going to the very expensive formula, mothers having to dilute the feeds to make ends meet, or – even worse – not having access to clean water, causing diarrhea and death. You say millions of babies are saved by formula, but breastfeeding experts will tell you that formula also kills on a large scale.

      Anne Hofstede

      March 3, 2014 at 4:17 am

    • Meagan, the evidence doesn’t support that millions and millions of children of babies have starved without formula in developing areas of the world. Far more women do breastfeed and breastfed infants are the least affected by famine of any member of the family. Infants and young children start to falter when they are started on solids or given substitutes for human milk because of bacterial contamination. Women who usually suffer under famine conditions more so than their fully breastfed infants. When something happens to the infants mother, wetnursing is often a viable option because more women have lactated and therefore can easily relactate in the event that something happens to the infants mother.

      In your case, the act of adoption itself is a marvelous gift to any child that has lost his parents. I’m not clear why your son needed formula since a 1 year old should have been able to eat foods and, if needed, drink cow’s or goats milk. Had there been a grocery store where you could have bought human milk (if you can make cow’s milk safe you can use the same processes to make human milk safe) I’m sure you adopted son would have grown equally well. And of course if you are in a developed area you have clean water and sanitation that makes the use of formula far less risky than in Ethiopia.

      What happens when you give to a formula fund in Ethiopia is that it disrupts breastfeeding and is far more deadly than it is here. When you have poor water and sanitation, the increase in the death rates between infants who are fed formula and those who are fed human milk are far greater. One study shows a five fold increase. The estimate is that there are 1 million more deaths per year from using formula under such circumstances. A far better donation would be to give to a fund that develops a local human donor milk bank. Again, lest you get squeamish – if you have ever been to a dairy farm (I grew up near many) you would realize the amount of sterilization procedures are required to make cow’s milk clean enough to not transmit disease — you can do the same thing for human milk.

      Plenty of studies have shown that malnourished children can catch up to a certain extent when they are provided better nutrition and a more enriched learning environment. That seems rather obvious. What is not clear is that you say your son “caught up” which seems to indicate that, if he were fed formula in Ethiopia that his malnutrition was due to having had to have been fed formula when not enough banked human milk was available.

      Susan

      March 4, 2014 at 4:46 pm

      • I do not think you understood the OP’s comment. OR, more likely, you chose to act as if you didn’t know what she was talking about. She stated she adopted her son at a year of she. Do you know how long an international adoption can take? Most likely he was in an orphanage overseas or some other type of foster situation. It’s not as if he were with his birth mother and able to breastfeed up until the day his new mom brought him home. He was likely on formula during that time. Besides, being from the situation he was in, who are we to say his pediatrician did not recommend to the adoptive mom to continue on formula past a year of age, due to prior poor nutrition or other factors?

        Erin

        March 2, 2015 at 1:45 pm

  8. I am all for breastfeeding. In fact, I was so committed to breastfeeding that I took 90MG of Domperidone everyday for one year so that I could exclusively breastfeed my baby. HOWEVER, you know as well as I do that statements such as “evidence continues to mount that formula feeding increases risk of Sudden Infant Death Syndrome” is misleading just as you point out about the study you are critiquing. Formula feeding does not increase SIDS, rather there is a stronger association of SIDS with formula fed babies is than breast fed babies. If you are going to critique a message as misleading, please be just as critical about your own message.

    Jen

    March 1, 2014 at 6:38 pm

  9. […] Reports on breastfeeding sibling study are vastly overstated, Breastfeeding Medicine — an official response to the much-discussed study that found less benefits to breastfeeding in the long term […]

    Saturday Surfing

    March 2, 2014 at 3:18 am

  10. I agree with Elisa, above. I work as an IBCLC in a large pediatric practice. With the public health push for breastfeeding, I have worked with many families who are interested in breastfeeding their second child, even though they formula fed their older child. I love their openness to change! However, these moms are much less likely, at least in my experience, to be committed to exclusively breastfeeding, and are also much less likely to persevere through breastfeeding difficulties in order to acheive exclusive breastfeeding for six months. It would be very interesting to know how much breast milk the breastfed siblings received, and for how long.

    Linda Ebright

    March 2, 2014 at 8:31 pm

  11. […] study in question doesn’t actually speak to any of these concerns— Bimla Schwarz and I have blogged about the limitations of the analysis and its implications. Yet these issues of shame, guilt, autonomy and informed consent are crucial to understand and […]

  12. […] I am absolutely appalled, though not surprised, that TIME, the New York Times, and other large name media outlets have linked onto a study published online in Social Science & Medicine that concludes there is no significant difference between siblings where one was breastfed and the other bottle-fed.  The study is flawed, biased, and lacks the peer review necessary to give the data any worth, which is both misleading and outraging the medical community. […]

  13. […] *) Kijk hier de uitzending terug Aanleiding was dit soort berichtgeving in de papieren en online media Het betreffende onderzoek is door velen al gebruikt om de vloer aan te vegen, bijvoorbeeld door: Breastfeeding Medicine, Physicians blogging about breastfeeding: Reports on breastfeeding sibling study are vastly overstated […]

    Auto | Eurolac!

    March 6, 2014 at 6:04 am

  14. Thank you for your post. I couldn’t agree with you more. Especially the following statement:

    “Mothers should have access to complete, objective, noncommercial information about what we know (and don’t know) about the risks and benefits of different feeding methods”.

    My question is, what constitutes “complete, objective”, and non-commercial ? As it is now, feel that most information about infant feeding is is incredibly biased towards breastfeeding. Further mores much of the information out there is misleading.

    Women are often told that they are putting their babies “at risk’ for serious conditions like diabetes, asthma, obesity, and cancers when the research is mixed at best as to whether breastmilk is protective. To support these claims, the breastfeeding and medical community often cites old, unconvincing research , ignores newer studies that don’t find breastfeeding protective, and commonly substitutes associations for causal relationships

    Of course women are going to feel guilty if they choose not to breastfeed or choose not power though all difficulties and pain; their choice may cause harm to their babies.

    And of course, health care workers are going to do their best to encourage women to breastfeed and power though all if they feel that their infants are “at risk” for chronic disease if formula is given. .

    Again, I too feel that women need accurate information, but as it is now, they get propaganda and scare tactics , which in turn puts way too much pressure on women to breastfeed and continue to breastfeed at all costs.

    I hope that the breastfeeding community will take a good hard, objective look at the evidence to support claims made in breastfeeding promotional materials, and come up with something that is more ‘complete and objective’, not to mention truthful and evidence-based.

    Anne Risch

    March 7, 2014 at 1:04 pm

  15. […] Response to Study that Benefits of Breastfeeding have been overstated. A new study published in the journal Social Science & Medicine suggested that some of the benefits of breastfeeding have been overstated. The study used sibling comparisons to estimate the effect of breastfeeding on long-term BMI/obesity, asthma, hyperactivity, attachment, compliance, and academic achievement and competence. Significant media attention surrounding the study has resulted in inaccurate and incomplete reporting on the proven impact of breastfeeding on public health, prompting responses from around the globe, including from the: “Reports on breastfeeding sibling study are vastly overstated” from Physicians on the Breastfeeding Medicine Blog. The biggest problem with this conclusion is that the study ignored anything that happened in these families before their children reached the age of 4, disregarding well-established links between ear infections, pneumonia, vomiting and diarrhea and the amount of human milk a baby receives. There’s strong biological evidence for these relationships, because formula lacks the antibodies and other immune factors in breast milk that block bacteria from binding to the infant gut and airway. For preterm infants, formula exposure raises rates of necrotizing enterocolitis, a devastating and often deadline complication of prematurity. And evidence continues to mount that formula feeding increases risk of Sudden Infant Death Syndrome. Furthermore, mothers who don’t breastfeed face higher rates of breast cancer, ovarian cancer, diabetes, high blood pressure and heart attacks. None of these outcomes were addressed by the recent sibling study. […]

  16. […] good thing. Breastfeeding advocates and researchers have done a good job of proving this, despite a shoddy study claiming that the ‘benefits’ of breastfeeding have been […]

  17. […] are in favour (or just Google it), and those which look at the design flaws of the study here, here, here and here.  Basically it raises some interesting questions about all sorts of different […]

  18. […] for child health and well-being were not statistically significant, the researchers say [2] https://bfmed.wordpress.com/2014/03/01/reports-on-breastfeeding-sibling-study-are-vastly-overstated/ [3] […]

  19. […] both baby and mother. Experts Alison Stuebe, MD, MSc and Eleanor Bimla Schwarz, MD, MS offer some helpful insights into the breastfeeding sibling study: namely, many of the protective health effects which are afforded by breastfeeding show up in the […]

  20. […] are in favour (or just Google it), and those which look at the design flaws of the study here, here, here and here.  Basically it raises some interesting questions about all sorts of different […]

  21. Reblogged this on Nutrition and Food Facts.

    Filippo Dibari's blog about Nutrition and Food

    August 12, 2014 at 11:33 am

  22. […] *) Kijk hier de uitzending terug Aanleiding was dit soort berichtgeving in de papieren en online media Het betreffende onderzoek is door velen al gebruikt om de vloer aan te vegen, bijvoorbeeld door: Breastfeeding Medicine, Physicians blogging about breastfeeding: Reports on breastfeeding sibling study are vastly overstated […]

  23. […] forms of randomized controlled studies and cohort studies in a hierarchy of study designs), one that ignores the essential and very important difference between those siblings: whatever changed in the family that led one child to be breastfed and another formula fed. We […]

  24. […] and epidemiologic methods seems incongruous with last spring’s gleeful reporting of the breastfeeding sibling study, which was widely reported as “confirming” that breast-feeding benefits have been […]

  25. […] [2] https://bfmed.wordpress.com/2014/03/01/reports-on-breastfeeding-sibling-study-are-vastly-overstated/ […]

  26. […] Still, if you were to ask my opinion these days on these matters, you would find me singing the praises of writers like Gayle Tzemach Lemmon or Amy Sullivan who point out that the breastfeeding cult has gone so far in one direction as to become profoundly anti-feminist and anti-choice. Not to mention the fact that formulas have come so far (and continue to improve) that most researchers now conclude that in countries with access to safe drinking water, there really are few (if any) long term differences between breastfeed babies and formula fed babies. The 2014 long term study of sibling groups certainly went a long way to dispel the notion that breas…. […]

  27. […] body of scientific knowledge supporting breastfeeding. It’s important to note that usually the studies these authors cite to make their points are flawed studies to begin with. Flawed studies = flawed outcome.  Breastfeeding wouldn’t be considered “a public health […]


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