Breastfeeding, IQ & Success: A few thoughts on the newest study to cause unnecessary worry for parents

“The longer babies breastfeed, the more they achieve in life,” proclaimed an article in The Guardian this morning. And around the world, millions of parents felt their stomachs lurch. Not because of what the study this article referenced actually said, but because they know, from experience, what this study means.

It means that we will continue to be beat over the head with “breast is best” proclamations that have fudge-all to do with our individual realities.

It means that we have to avoid social media for the next few days, unless we want to silently endure smug status updates, or be labeled “defensive formula feeders” if we dare offer an alternative point of view.

It means that those of us who are newly minted moms and dads, still anxiously watching our babies’ chests rise and fall and worrying about the color of their feces and every ounce they gain, will wonder if they should have tried harder/could have done something differently/might have chosen another path.

It means we will witness another media cycle where reporters regurgitate the same mommy-war bullshit, throwing in condescending caveats about how it’s “still a mother’s choice” whether or not she nurses her child.48fc15010a26b03f8586826f99699143

It means that society is still, as always, missing the damn point.

As for the study itself…. what it means is a lot less obvious. Here is the summary:


A prospective, population-based birth cohort study of neonates was launched in 1982 in Pelotas, Brazil. Information about breastfeeding was recorded in early childhood. At 30 years of age, we studied the IQ (Wechsler Adult Intelligence Scale, 3rd version), educational attainment, and income of the participants. For the analyses, we used multiple linear regression with adjustment for ten confounding variables and the G-formula.


From June 4, 2012, to Feb 28, 2013, of the 5914 neonates enrolled, information about IQ and breastfeeding duration was available for 3493 participants. In the crude and adjusted analyses, the durations of total breastfeeding and predominant breastfeeding (breastfeeding as the main form of nutrition with some other foods) were positively associated with IQ, educational attainment, and income. We identified dose-response associations with breastfeeding duration for IQ and educational attainment. In the confounder-adjusted analysis, participants who were breastfed for 12 months or more had higher IQ scores (difference of 3·76 points, 95% CI 2·20–5·33), more years of education (0·91 years, 0·42–1·40), and higher monthly incomes (341·0 Brazilian reals, 93·8–588·3) than did those who were breastfed for less than 1 month. The results of our mediation analysis suggested that IQ was responsible for 72% of the effect on income.


Breastfeeding is associated with improved performance in intelligence tests 30 years later, and might have an important effect in real life, by increasing educational attainment and income in adulthood.


In laymen’s terms, these researchers interviewed a large group (3493) of 30-year-olds who were part of a larger study which began in 1983, when these folks were born. They chose these subjects based on the fact that they had a significant amount of data on their infant feeding patterns and follow-up data, and because they agreed to be interviewed for the project. They gave them IQ tests, and found that those who had been at least “primarily” breastfed for 12 months scored about 3 points higher, on average. (This doesn’t mean that every single formula-fed subject scored lower, or that every single breastfed subject scored higher – we are talking about aggregates here, not individuals.) The breastfed subjects also tended to have a little under a year more schooling and make a bit more money per year.

The researchers (and the media) claim that this is the first study to so clearly show a causal (and dose-related) relationship between nursing and intelligence/success in later life.

The critics claim that because they did not control for maternal (or paternal, for that matter) intelligence, the results are not so convincing. I agree that parental IQ is far more important than most of what they did control for, but they did at least control for a fair number of confounding factors, like socio-economic status, parental education level, income, birth weight, and so forth. They also had the advantage of using a cohort for which breastfeeding wasn’t associated with class; in other words, people across all socioeconomic groups breastfed and didn’t breastfeed, ruling out the concern that some of these positive effects would merely be associative (rich people breastfeed, rich people have better opportunities/resources, etc.).

There could very well be a correlation between those in this study who were breastfed and better outcomes in terms of IQ and success. I do have some questions, though:

1. What were the formulas like in Brazil, circa 1982?

I couldn’t find anything regarding the types of foods used as breastmilk substitutes in Brazil in 1980-1983. At best, they were the same or similar to American brands, which were somewhat different than how they are now. Not vastly so, but enough that it could potentially make a difference. (Then again, most of us were raised on these formulas and don’t seem too damaged because of it, so…. make of it what you will.) The study did not specify what these babies were eating in place of the breastmilk: properly prepared, commercial infant formula? Homemade formulas? Animal milk? This does matter. We need this info before we can begin to make assumptions about the risks of formula, because for all we know we may not even be talking about formula.

2. What, exactly, were the politics of breastfeeding in Brazil, circa 1982?

The authors talk about breastfeeding not being associated with SES in this cohort, but what did cause women to choose formula over breastfeeding, and vice versa?

According to a 2013 paper in Revista de Saude Publica, “Campaigns promoting breastfeeding began in Brazil in 1981 with the National BF Promotion Program. The 1980s was marked by significant advances in legal protection for BF, with the approval of the Brazilian Code of Marketing of Breast Milk Substitutes and the inclusion of the right to 120 days maternity leave in the Constitution.” I also found references to a Brazilian television campaign which promoted breastfeeding, initiated in the early 1980s which featured spots aimed at various demographics, using language, images and celebrities that would appeal to these specific groups. This implies that the author’s assertion that their study was able to negate possible confounding factors might be overstating it a bit. Socioeconomic status is not the only thing that could give a child a slight bump in advantages associated with success later in life. If there were fundamental differences in the mothers who chose to breastfeed back in 1983 Brazil, those differences would matter for the purposes of this study.

3. Why is a 3-point bump in IQ and a slightly higher income so important for public health, anyway?

The authors state that these findings are important on a public health and economic level. But let’s get Orwellian here, for just a second: if everyone is breastfeeding, then everyone is getting the 3-IQ point and 1-more-school-year advantage. Everyone is making more money per year.  The playing field is even. I nearly failed Econ, so correct me if I’m wrong, but don’t you need “have-nots” to have “have’s”? If the whole country is smarter, then I guess you’d have an economic advantage… but the breastfeeding research world is quite international in scope. After all, our recommendations come from the World Health Organization, not the Every-Country-For-Herself Organization. If we all are smarter from breastfeeding, that’s great – but it’s not much of an economic argument, is it?

Obviously, I am being entirely facetious with the a paragraph. I am far from convinced that breastfeeding makes you smarter or more successful. But I want to point out how convoluted these arguments in favor of breastfeeding truly are. How offensive they are. The implication is that our life’s worth is measured in IQ and financial reward. How about a study showing how traits like patience, kindness, acceptance, creativity, ingenuity are tied to infant feeding?

This study was funded by public health agencies, so these questions are important. When we confuse public health messaging with messaging about IQ and “success” (a quite narrow definition of it, incidentally), we are heading down a very slippery slope.

4. Why aren’t we asking why and how, instead of droning on about the same old tired shit?

If – and this is a strong if – the author’s hypothesis that the fatty acids in breastmilk may be the cause of this bump in IQ (which they imply is what provoked the longer time in school and the greater income – again, sort of a sloppy connection, considering there’s many people with incredible IQs and low levels of education and career success), then why is the take-away “see, everyone should breastfeed!” and not “how can we improve breastmilk substitutes so that all babies get this advantage?”

The study itself is only noteworthy because it followed a lot of people over a lot of years. But remember: associative data is always associative data. Sure, larger groups make for more dramatic assumptions, but at its core, this is just like any other infant feeding study: it shows that there is a slight advantage for people who were breastfed. It doesn’t show how, it doesn’t show why, and it doesn’t tell us squat about anything on the individual level. It does not in any way prove that tour brilliant formula-fed child would have been 3 points more brilliant if you’d managed to breastfeed her. And even if it did prove without a doubt that breastfeeding added 3 points to every single baby’s IQ, it would not tell us how many IQ points a baby might lose if she was starving for the first 6 months of her life, or if her mother was crying and absent all the time, hooked up to a pump, instead of interacting with her. Or if the breastmilk she was getting was laced with any number of substances. Or if her mom didn’t eat enough kale. Or too much kale. Or if her mom ate dairy and she had an undiagnosed MSPI. Or if her dad was an asshole. Or if she was abused and dropped out of school and did drugs that dulled her senses, rendering her unable to even take the bloody IQ test.

My point is, no matter what this study tells us (and it doesn’t tell us anything we hadn’t already heard), the more important thing is what it doesn’t tell us. Life is about so much more than what you eat in the first few months of your life. That doesn’t mean it doesn’t matter – otherwise I wouldn’t be so crazy about making sure research is done to improve formulas and make sure they are as safe and healthy as possible – but provided your child us getting adequate nutrition, there are just so many other things that can help them along or trip them up.

And don’t hate me for saying this, but you are only one of them. Sure, you’re who they are going to be talking about on the therapists’s couch in 30 year’s time, but they aren’t going to be mad at you for not breastfeeding. They are going to be mad that you missed their school play, that you embarrassed them in front of the cool kids in the parking lot of the mall, that you didn’t support their life’s dream to be a potter specializing in tiny, thimble-sized pots.

So do yourself a favor: throw out the newspaper screaming about breastfed babies “growing up to smarter, richer adults”, turn off the Today Show with its smug newscasters, and talk to your child. Because that’s they want. Not your breastmilk. Not 3 IQ points. They want you, and all your imperfections, and all your concerns for their welfare and your anxieties and your dorkiness and your dysfunction. They just want you.

Until they turn 13. But that’s another story.





Suzanne Barston is a blogger and author of BOTTLED UP. Fearless Formula Feeder is a blog – and community – dedicated to infant feeding choice, and committed to providing non-judgmental support for all new parents. It exists to protect women from misleading or misrepresented “facts”; essentialist ideals about what mothers should think, feel, or do; government and health authorities who form policy statements based on ambivalent research; and the insidious beast known as Internetus Trolliamus, Mommy Blog Varietal.

Suzanne Barston – who has written posts on Fearless Formula Feeder.

Related Posts Plugin for WordPress, Blogger...

16 thoughts on “Breastfeeding, IQ & Success: A few thoughts on the newest study to cause unnecessary worry for parents

  1. Also, it ignores the fact that so many other things will have a FAR greater impact on your child than breastfeeding. The way parents support education, or model good work ethic, or opportunities provided to the child, good sleep and general health habits, and stable and healthy home life–these things all have substantial effect on a child’s ultimate success. A few extra IQ points pale in comparison to these things. There seems to be disproportionate emphasis on breastfeeding when so many factors contribute to a person’s success (and happiness) in life.

  2. The other ‘confounding factor’ that the study ignored (apart from… well… pretty much all confounding factors): Self-reported data. I highly doubt that these women were kept under strict monitoring and lock-and-kay to see how they were feeding their babies. If there was a big public push for breastfeeding a few years earlier then there’s a major risk that these women who were participating in a feeding study, seeing this push could possibly have felt pressure to lie to the researchers. After all, if the propaganda is telling you that formula is second best and you’ve got some high-and-mighty academics asking you questions, who wouldn’t feel pressure to conform?

  3. Even assuming the study is flawless, which none really are, IQ is a terrible measure of impact. While the difference of 3 points may have been significant within the study, for most people 3 IQ points hardly matter (a classic case of “statistically significant, but clinically trivial). IQ is a measurement specifically designed to follow a normal curve distributed around the average of roughly 100. This means that most of the population is going to fall in some range closely surrounding 100, so 3 points (say 90 vs 93 or 107 vs 110) really does not move you that far along the curve. Those points really only “matter” at the ends of the curve (say 62 vs 65 or 170 vs 173) in which case, you are likely to be in a group where breastfeeding is the least of your developmental concerns. I can think of many reasons why breastfeeding may be a great idea (for some, if they so choose), but insignificant IQ point gains need to stop being so heavily propagandized.

  4. Thank you for this! I felt horrible all over again after hearing about this study as I debate whether to continue making myself crazy pumping and change to all formula. I most likely have IGT and every ounce I have pumped has been hard won. I feel like I have missed out on my baby and I doubt that is “best.” But then studies like these make you doubt myself even though I know rationally it’s not telling us anything much. It’s just nice to see a balanced review of the study. One caveat though: I am a physician and the email I got about the study said they did control for maternal IQ. You say they didn’t. I’m curious which is true. If they didn’t, I’d like to write to journal watch about their error because that’s pretty important.

  5. I also forgot to mention another thing I noticed about the study. A full 41% of their study participants dropped out of the study, meaning they were initially studied but were lost to follow up 30 years later. In any other study this big a drop out rate is seen as a huge flaw because they could’ve swayed the results significantly. I have heard no mention in the media of this huge flaw either! Why did they drop out? This in itself confounds the data.

    • There were 30 years in between. I imagine they couldn’t find everyone. Also, frankly, if some scientist looked me up tomorrow and said “Hey, we want to find out how long you were attached to your parent’s nipples and how that impacted your life”- I’d slam the door in their face!

      I agree that is another factor, though, you’re getting results from people willing to give the results (and it’s all self-reported), which can impact things there.

  6. I read the study and I found another troubling thing: they didn’t report the number of people in each average (N). They said that there were very few people who breastfed longer than 9 months or so, but then they used statistics to find an average for them. They also published a graph which shows that family income had a much greater impact on IQ than length of breast feeding:

    • Did they not even report it in the full article? They must’ve, surely!

      But, yes, if there’s a significantly smaller number of breastfeeders, that’s a pretty big problem. It’s been over a year since I even touched statistics so I can’t remember the exact reasons why, but for one thing it’s more susceptible to outliers.

      (also, seriously, *3 points* of IQ? Who cares? That’s hardly the difference between a genius and a dullard!)

  7. “How about a study showing how traits like patience, kindness, acceptance, creativity, ingenuity are tied to infant feeding?”
    That would be interesting indeed, if such traits could be measured. However, what is known is that FF babies are statistically more likely to end up in the criminal justice system … presumably more likely also to be less kind and accepting (if one’s a criminal, that is).
    Saying that though, the Yorkshire Ripper and Hitler were probably both breastfed, so it’s all quite random really.
    Also this study shouldn’t be worded with “achieve more” in life, or have “greater IQ” – it should really talk about “normal” achievement and IQ, seeing as BF is species normal. Ever heard of a shrew feeding its young rhinoceros milk??? Or the other way round? Guess we’d have massive shrews and tiny rhinos ….
    Or should it be worded that formula “lowers IQ” and leads to “less achievement”? Just putting some thoughts out there ….

    • Can you link me to the study that shows that what is “known” is that FF babies are statistically more likely to end up in the criminal justice system? I’d be very interested in seeing it.

      Also, your comparison w/the animals is rather flawed. First off, no one is advocating giving human babies straight animal milk. Formula has cow’s milk in it, sure, but that is just the base. That is why formula was a such a useful development in the 20th century – babies DID die from being fed animal milk as a breast milk substitute. Secondly, even if we WERE using straight cow’s milk, the weight of the animal is a non-issue. What’s important is the ratio of fat/protein/carbohydrate. If newt’s milk was close enough to rhino milk in that respect, it might not be that bad.

      • – study, I admit which is about behavioural problems rather than criminality. However, many criminals we know had behavioural problems as children. – another one about the long-chain fatty acids and effect on behaviour
        A study by Loennerdal, 1994, talks about the toxicity of manganese on the baby’s brain – and higher levels of manganese are found in formula. It’s more about ADHD – but of course, having ADHD is a risk factor for later criminal behaviour.
        And simply that more criminals tend to have lower IQ and are from lower socio-economic groups, and these groups tend to use more formula.
        But then again, formula can also produce brilliance as well. I mean, have you seen that advert they show in the Philippines of the musical prodigy, a little girl voilinist, who drinks a certain brand of follow-on milk? Surely if one’s child drank this, then they’d end up very, very clever, I can’t imagine the formula companies and all the “social responsibility” they claim would mislead us at all?
        The animal milk thing – I was just messing. Perhaps Nestle and Danone, etc. will do some research to find out if there’s a milk closer than cow’s to human milk to improve formula. Though that would cost them a bit – though surely their profit margins aren’t THE most important, it’s the welfare of babies, innit?

  8. I came across your website with some curiosity because although I have breastfeed my children and given them formula, my disappointment in your website is no different than those who breastfeed and only believe that breastfeeding is best. You have a book and tshirts to sell, so frankly I am unsure of your message, maybe it is just about selling your stuff? How about as women we celebrate that there is a wide range of what is acceptable. My opposition to formula companies has always been their marketing to women who may not afford it but then provide trinkets and trash to new moms while they do not donate any formula to food banks. If you can afford formula,, cool but this conversation is not as simple as you make it seem.

  9. I love this website, so don’t get me wrong here. Thank you for what you do! I can’t help being pedantic, though: I can see why you struggled a bit with econ. 🙂 The central insight of microeconomics is that voluntary trade is mutually beneficial. In other words, we don’t actually require have-nots in order for some people to flourish. Everyone can, in fact, be better off all at the same time if they all become more productive. A population-wide IQ bump could absolutely make everyone richer than they are today.

    What frustrates me most about Victora 2015 (this new study) is that it fails to even mention the discordant sibling studies (Evenhouse 2005, Der 2006, Colen 2014), which compare groups of children who were breastfed to a control group of their own siblings who were not breastfed. These studies are of a type generally considered by empiricists to be methodologically superior to studies like Victora 2015, and they find very trivial to *no* effect on IQ. The Victora researchers should, in my opinion, have acknowledged the existence of the discordant sibling research and grappled with their findings in light of these contrary findings.

Leave a Reply

Your email address will not be published. Required fields are marked *