New breastfeeding study shows that maternal education, family income and birth weight have a greater impact on IQ than breastfeeding


Not surprisingly, the authors of a new study on breastfeeding and IQ led with the information likely to generate the best headline, Breastfeeding ‘linked to higher IQ’:

A long-term study has pointed to a link between breastfeeding and intelligence.

The research in Brazil traced nearly 3,500 babies, from all walks of life, and found those who had been breastfed for longer went on to score higher on IQ tests as adults.

Experts say the results, while not conclusive, appear to back current advice that babies should be exclusively breastfed for six months.

But the study, Association between breastfeeding and intelligence, educational attainment, and income at 30 years of age: a prospective birth cohort study from Brazil, which shows that breastfeeding might have an impact on IQ of up to 3.76 points also demonstrates that just about anything else has a far greater impact on IQ than breastfeeding.

Consider this graph showing the impact of breastfeeding on IQ stratified by family income:

Lancet graph

The graph shows several interesting things:

1. Breastfeeding for less than a month has no impact on IQ
2. Breastfeeding for more than a year has no impact on IQ in infants from high income families.
And, most importantly, the impact of breastfeeding on IQ is dwarfed by the impact on IQ of

Maternal education

maternal education v IQ

Birth weight

birth weight v IQ

Family income

family income v IQ

(All graphs shows babies that were breastfed for 6 months.)

Arguably, if a mother wants to have the greatest impact on her baby’s IQ, she should go back to work rather than breastfeed.

The BBC piece acknowledges the contribution of many variables to IQ:

Regarding the findings – published in The Lancet Global Health – they stress there are many different factors other than breastfeeding that could have an impact on intelligence, although the researchers did try to rule out the main confounders, such as mother’s education, family income and birth weight.

Dr Bernardo Lessa Horta, from the Federal University of Pelotas in Brazil, said his study offers a unique insight because in the population he studied, breastfeeding was evenly distributed across social class – not something just practised by the rich and educated.

Most of the babies, irrespective of social class, were breastfed – some for less than a month and others for more than a year.

Those who were breastfed for longer scored higher on measures of intelligence as adults.

They were also more likely to earn a higher wage and to have completed more schooling…

Dr Horta believes breast milk may offer an advantage because it is a good source of long-chain saturated fatty acids which are essential for brain development.

But experts say the study findings cannot confirm this and that much more research is needed to explore any possible link between breastfeeding and intelligence.

In Brazil the impact of income of breastfeeding rates is very different than in higher income countries. In the US, for example, breastfeeding is correlated with family income; the higher the family income, the greater the likelihood that an infant will be breastfed. In Brazil, breastfeeding rates were highest at either end of the income spectrum, the very poor were as likely to breastfeed as the very rich. Indeed 80% of the children in the study were breastfed at for at least a full month. And that raises an important question.

In this study, the authors assume that breastfeeding in an independent variable that depends almost entirely on maternal desire. But in a country where breastfeeding is the norm, it may be that the duration of breastfeeding reflects the success of breastfeeding. In other words, women who breastfed for only a short duration stopped not because they didn’t want to continue, but because their babies were showing signs of malnutrition. The fact that babies breastfed for less than a month had lower IQ scores at age 30 might be a reflection of malnutrition in the early weeks, not a lack of breastmilk.

This is a good study. The authors followed a large cohort of infants through adulthood. They carefully controlled for confounding variables. They showed that breastfeeding up to 12 months (but not longer) has a small but measurable impact not merely on IQ, but also on educational attainment and income. But the study also has some significant limitations. The authors did not control for the most important confounding variable, parental IQ. They assumed that income and educational attainment were proxies for IQ, but they did not demonstrate that. One third of the study participants were lost to follow up and they may differ in important ways from those who were available for follow up.

Ultimately, though, the authors showed that the impact of breastfeeding on IQ pales in significance to the impact of everything from birth weight to maternal educational attainment to family income.

The take away message should be:

If you want to improve your future child’s IQ, you should stay in school, work hard and get good prenatal care so you can have a larger infant. If you want to improve your child’s IQ slightly beyond that, you can breastfeed. But it may not be only the breastfeeding that impacts IQ but whether the mother can produce enough breastmilk. Breastfeeding a baby who isn’t getting enough to eat may actually be far worse than not breastfeeding at all.

111 Responses to “New breastfeeding study shows that maternal education, family income and birth weight have a greater impact on IQ than breastfeeding”

  1. Alex Tulchner
    May 5, 2015 at 11:49 am #

    Thank you. That’s all.

  2. sdsures
    March 30, 2015 at 5:01 pm #

    How exactly was IQ measured in this study (both parents and babies)? When I was studying psychology at uni, we were taught that the concept of IQ is nebulous at best.

  3. Seattle Mom
    March 24, 2015 at 11:33 am #

    I liked this article about the struggles of breastfeeding as it was very honest. The comments were all supportive, which was refreshing:

  4. Staceyjw
    March 24, 2015 at 6:11 am #

    So they lost a third of those they were studying, and didn’t even control for parental IQ?

    In nations where the rich stay rich, and the poor stay poor, success doesn’t always mean high IQ. One could be a genius, but being born in a favela generally means being poor your whole life. You can also be well below average IQ wise, gradulate Ivy league, and end up a CEO, or even president (hello GWB!).

    I know that the wealthy get a big IQ bump from all of the privileges they enjoy (ie, food security, etc), but parental IQ still matters. I can’t imagine not controlling for it.

  5. Liz Leyden
    March 23, 2015 at 7:37 pm #

    Recently posted on a Mom’s blog I follow- Fed is Best.

  6. Russell
    March 22, 2015 at 5:38 am #

    By far the worst shortcoming is the failure to control adequately for parental IQ. All of the other confounders especially maternal education and including birthweight are also under genetic influence.
    The likelihood that you can make significant changes to your child’s IQ excepting trauma seems pretty low.
    This is not to say that think nurture is worthless, it clearly isn’t, just that it’s role in attaining full intellectual potential is scientifically dubious.

  7. Francesca Violi
    March 20, 2015 at 1:07 pm #

    How is weight at birth related with higher IQs in adulthood? I mean, I understand that small weight at birth caused by placental issues, diseases or severe prematurity might impact statistically on some aspects of development. But when we talk healthy, full term babies, is it really significantly likely that a 3,5 kg newborn will be smarter than a 3 kg? Being bigger at birth might not simply mean you have bigger parents, or more generally reflect the genes in your family, ethnicity etc.? I am curious, also because my own children were born at term but pretty small, 2.7 kg (girl), 3.1 kg and 3.3 kg (boys).

    • fiftyfifty1
      March 22, 2015 at 9:44 am #

      ” is it really significantly likely that a 3,5 kg newborn will be smarter than a 3 kg? ”

      On a population level, yes. It’s not a big difference in IQ, and it is not going to hold for individuals, but on a population level, yes.

      It’s similar to adult height and IQ. Short adults, on average, have lower IQs than tall ones. The reason is that shortness can be caused by 2 different things: Genetic shortness or genetic tallness plus adversity (poor nutrition, childhood illnesses etc). People who are short because of genetic shortness don’t experience IQ loss, but those who are short because of adversity often do. But again, the effect is small.

      I’m quite short myself, and I’ve also never had a baby above 3,5 kg. I suppose my whole family is screwed 😉

  8. namaste863
    March 20, 2015 at 7:53 am #

    There are about a million confounding variables here. One I don’t think they adequately controlled for was the test itself. As far as I can tell from reading the methodology of the study, they only administered the IQ test once. I would administer it an absolute minimum of five times per party and compute the mean scores.

    • sdsures
      March 30, 2015 at 5:07 pm #

      Or the median scores. Mean is affected by changes in the extremes.

  9. March 20, 2015 at 3:02 am #

    In other words, women who breastfed for only a short duration stopped
    not because they didn’t want to continue, but because their babies were
    showing signs of malnutrition. The fact that babies breastfed for less
    than a month had lower IQ scores at age 30 might be a reflection of
    malnutrition in the early weeks, not a lack of breastmilk.

    Mightn’t it also be due to the necessity of returning to work as soon as possible, for poor women? Children of the favelas, with less opportunities for the benefits that higher income families could provide, could also be at risk for developmental problems which could impact IQ later, no?

    Also, what was the situation 30 years ago regarding the availability of formula, its quality, and price, for Brazilian women? Breastfeeding, as a “successful norm” might simply have been the only option, not the preferred one.

    I have no idea what life was like, for the rich or the poor, in Brazil 30 years ago, but I am willing to bet that it’s a lot better now.

    • Mariana
      March 20, 2015 at 4:33 pm #

      Yes, 30 years ago formula was not so common, and mostly given by doctor prescription. It was expensive too. Children who could not be breastfed were offered regular cow milk or powdered milk (no formula) often thickened with maize. Children also were given solids early (even breastfed ones), sometimes at 4 months or earlier. Even mothers who breastfeed usually don’t do it exclusevely, or only do it for a small period. It’s common to offer a bottle at night so the baby will sleep longer, often times with oatmeal or maize to make it thicker.

      Culturally, breastfeeding is the norm, but not exclusive breastfeeding.

      Source: born and raised in Brazil.

  10. Ellen Mary
    March 19, 2015 at 11:24 pm #

    Great analysis. 3 points isn’t anything. Seems like it could be used to say that the greatest benefit/cost is to nurse for a year and no longer at the highest income levels. My only complaint is that this is YET another study focusing on BF as an act of service designed to create a better product, instead of a relationship and also a maternal health choice following pregnancy that could have maternal health benefits as well as risks.

    • Cobalt
      March 19, 2015 at 11:34 pm #

      How is a breastfeeding mother’s relationship with her child different or better than a bottle or formula or combo feeding mother’s? Is it really different? Are the differences positive? Are the differences close to universal or overwhelmingly individual?

      I’ve done all of the above, so I know my answer, but I really want to hear yours.

      • Ellen Mary
        March 20, 2015 at 7:52 am #

        I am just saying that the child isn’t a product to be improved. Sure it is a different relationship. I am not going to say it is not different. In some ways for me the differences are negative, my relationship tends to be more ‘business only’ as well as my baby’s. My husband does more actual snuggling, I imagine if feeding were taken out of the equation, from my breast, we might snuggle more. As a positive I felt very good about having to check in with my NB every 2-3 hours & I still feel pretty good about it, it keeps me feeling very connected to him. But every relationship between every mother & babe is different. Am I going to say that my relationship with my baby would be precisely & exactly the same if I were bottle feeding? It wouldn’t be but it would be equally good.

        • anh
          March 20, 2015 at 3:46 pm #

          I don’t doubt that one’s feeding method will have a variety of negative and positive impacts on the relationship. Many women describe loving nursing and enjoying the down time it gave them but sometimes feeling super touched out by it. So many moms describe the time they finally gave their baby a bottle as the first time they truly felt connected with their baby.
          But I really don’t think there is a point of “studying” this impact. Moreover, I think it’s insanely impossible to begin to study it from anything other than maybe a “soft” angle like…I don’t even know…sociology? Like, there are as many different mother-baby relationships as there are mother-babies. billions upon billions upon billions. I’d love to read a collection of essays wherein mothers describe feeding their babies and what it meant. But I can’t see any point in diverting actual research dollars towards “unpacking” that relationship

          • araikwao
            March 22, 2015 at 5:02 pm #

            What does “touched out” mean? Someone else used that phrase in the comments, is it an American thing?

          • anh
            March 22, 2015 at 5:32 pm #

            I think it’s an American thing. It’s that feeling you get when you’ve had another human touching you, either attached to your breast, in your arms, hanging on you all day, that you feel like you’re losing your shit

          • demodocus' spouse
            March 22, 2015 at 6:20 pm #

            Don’t know if it’s only American, but that’s about it. I managed to get to that state with both my son and his father. Sometimes, Demodocus has just been holding my hand, elbow, or shoulder too darn much for one day, so I ask him to use his cane for a while.

          • araikwao
            March 22, 2015 at 10:12 pm #

            Oh yeah, that makes perfect sense! I totally remember that feeling too..

    • Valerie
      March 19, 2015 at 11:35 pm #

      “much more research is needed to explore any possible link between breastfeeding and intelligence.”

      I was just thinking… what for? Can’t we spend limited research funds on investigating actual health outcomes? We’re not talking about intellectual disability here, but a couple of points at best.

    • Pink
      March 20, 2015 at 10:00 pm #

      Why not focusing on improving formula instead of studying the impact of breastfeeding again and again without any benefit other than pushing lactating even when impossible for some moms.

      • Nick Sanders
        March 20, 2015 at 10:43 pm #

        Because that would make sense and undercut their ideology/business model?

        • Dr. Chiara
          March 22, 2015 at 11:25 am #

          So you prefer that women spend money on better formula instead of being free to be shown by medicine (it’s easy: just read something about lactation cycle from stimulation to prolactin release after oxytocin and successive milk production in the breast to understand how it works) how to do and enjoy the most natural and healthy thing in life? If a doctor tells a women to give breast each 2-3 hours and 10 mins for each breast or to give her baby water or pacifier when he cries, THIS is killing her breastfeeding, not that she “simply cannot breastfeed”; physiological impairments to breastfeeding are very rare and well documented, and they cannot explain the huge rate of women who are not able to perform such a natural thing; maybe psychological and/or emotional blockages are more probable to explain a percentage of this. And I personally know a lot of women who had “few” milk at the beginning or they reduced their milk production after 2 months just because they were following stupid time schedules and were more worried about their babies sleeping all night long than to ensure the adequate stimulation of their milk production overnight or followed the advice to “put the pacifier in their babies mouth to calm them down” instead of putting their breasts in their babies mouth.
          It’s not a mystery that their milk “disappeared” or “never came”, it’s just bad information and confounded attitude in a good percentage of cases. And, IMHO, offering a better (and scientific) information costs definitely less than trying to improve formula (which, anyway, can be improved and improved as much as you want, but it will NEVER replace a fundamental “ingredient” of breast milk: ANTIBODIES that exactly that child’s mother produces for her baby!!).
          And, btw, the only BUSINESS here is exactly formula production/innovation: THIS moves economy and causes competence and price war, not a FREE thing as breastfeeding (it’s free, it’s good, it’s healthy and it naturally improves the affection, the positive attachment to the mother and skin-to-skin contact).
          I personally agree with the author of this article that the study has some methodological problems and I think there are some more studies showing more evidence that lactation is healthier and better than the formula than this, but I don’t understand how is it possible than in 2015, when it’s possible to study almost any issue for any person, there is still such an ignorance as saying that someone keeps on “pushing lactating even when impossible for some moms”…when for decades what happened was exactly the opposite: someone was pushing mothers to quit lactation (without giving them the necessary information to make it successful) in order to BUY this or this other brand of formula!

          • fiftyfifty1
            March 22, 2015 at 12:13 pm #

            What do you make of the discordant sibling studies that show NO difference between breast and formula in the following outcomes: intellectual abilities, weight, behavioral problems, allergies, illnesses and show WORSE outcomes for breastfeeding with asthma?

          • Amy Tuteur, MD
            March 22, 2015 at 12:43 pm #

            Tell us which of the breastfeeding studies have you read in full and analyzed. None, right? Your personal opinion on breastfeeding is not particularly valuable. Show us the data.

          • The Computer Ate My Nym
            March 22, 2015 at 12:56 pm #

            being free to be shown by medicine

            No shade of patriarchy in that statement, nope, not a bit. “Medicine” doesn’t show anyone anything. Doctors can and should present the options to the patient, listen to what he preferences are, explain the risks and benefits of each course of action, and make a recommendation based on his or her knowledge of the above which the patient can accept or reject.

            Describing it as “being free to be shown” is a rather creepy and Orwellian way to put it. How is being forced to breastfeed no matter what you preference being “free”?

          • Nick Sanders
            March 22, 2015 at 1:09 pm #

            So, you’re saying she should give up 4 to 6 hours of her life every day for marginal benefits at best? That’s really her choice, not yours, isn’t it?

            As far as the “for that baby” bullshit about antibodies or any other component, it’s ridiculous. One person’s body cannot read the state of another’s, let alone custom tailor anything to that. Once the baby is out and there is no direct connection, any changes to it’s condition are completely unknown to the mother’s biology. And yes, breastmilk does contain antibodies, but they aren’t special antibodies designed for the babies needs, they are whatever antibodies the mother has that can get into the breast milk. If the baby encounters a disease the mother never did, well, it’s SOL.

          • Elizabeth A
            March 22, 2015 at 1:41 pm #

            Breast feeding is free only if you discount the value of a woman’s time. It can get quite expensive if you appropriately value that commodity.

            Breast feeding is especially financially challenging in countries like the U.S., which have no provisions for guaranteed or paid maternity leave. (FMLA applies to about 50% of employed women at best, and does not guarantee any compensation during leave time.) It really should not be a mystery why so many women in the U.S. stop breast feeding when their children are 2-3 months of age – that’s the absolute longest that most of them have available for maternity leave.

            If you have to be functional at work all day, getting a good night’s sleep for yourself is not a trivial concern, and that does lead a lot of women to be concerned about getting their babies to sleep through the night very early.

            But by all means. Rummage around for psychological or emotional blockages to explain a phenomenon that basic economics makes crystal clear.

          • Somewhereinthemiddle
            March 22, 2015 at 1:50 pm #

            “physiological impairments to breastfeeding are very rare” – You need to site a credible source for this information in order for anyone to take you seriously and BFI and LLL are not credible sources. From my experience, this dangerous misinformation not to mention the fact that you are assuming that all women desire to breastfeed which is not the case.

            “If a doctor tells a women to give breast each 2-3 hours and 10 mins for each breast or to give her baby water or pacifier when he cries” – Not sure where you came up with this but I don’t know *anyone* who has been advised by a physician to give a baby water in more than 30 years. Maybe it is standard in other countries and if it is, it is poor practice not because it fails to enourage breastfeeding but that it discourages feeding a hungry baby at all.

            “not a FREE thing as breastfeeding (it’s free, it’s good, it’s healthy and it naturally improves the affection, the positive attachment to the mother and skin-to-skin contact). ” – More misinformation. Breastfeeding is absolutely not free. As a breastfeeding mother myself, the additional food I consume while breastfeeding costs money. The pump I use costs money, the bottles cost money, the storage bags cost money, the replacement parts for appropriately sized flanges, tubing, and other pump parts cost money. For working mothers, their time has a measurable monetary value. Breastfeeding is *not* free.

            “there is still such an ignorance as saying that someone keeps on “pushing lactating even when impossible for some moms”…when for decades what happened was exactly the opposite” – Sure, this may have happened in the past but that was decades ago. In most parts of the world, there are huge public campaigns and policies to promote breastfeeding. This assertion is terribly outdated.

            I’ve breastfed three children for a total of 5 years. I prefer to breastfeed but I do NOT believe in pushing breastfeeding on other women with lies and misinformation. Go back and double check everything that you have spouted here and I think you will find that you have been suckered in by rhetoric.

          • pinktulip99
            March 24, 2015 at 10:30 am #

            A midwife in the hospital where I gave birth said “he’s thirsty, give him some water” when he was 2 days old. That was only 2 years ago, so it does still happen 🙂 this is in Germany. Actually, all the midwives contradicted each other, but luckily ‘cos my German wasn’t great at the time and I was on a private health insurance (so had to pay for midwife visits myself once out) they left me alone and I just got on with feeding him myself. In terms of it not being “free”, well, it is kind of free, but I need to eat loads of cake and ice-cream as it’s made me as thin as a hound!

          • Sarah
            March 22, 2015 at 3:32 pm #

            As if you have the remotest idea whether formula will contain antibodies in the future.

          • demodocus' spouse
            March 22, 2015 at 6:39 pm #

            My doctors pushed breastfeeding. I managed to suppress my growing sense of violation enough to breastfeed my child for 11 months. Until the time I curled up on my bed shuddering at the thought of either son or husband touching me ever again. I could never bond over nursing, because I always hated it.

          • Nick Sanders
            March 22, 2015 at 8:26 pm #

            Wow, that’s truly awful. I’m sorry that happened to you.

          • demodocus' spouse
            March 23, 2015 at 2:42 pm #

            Eh, there are worse things, but thank you.

          • Rebecca
            March 22, 2015 at 7:17 pm #

            Who are you to decide what is “free, good and healthy” for another woman or family? Breastfeeding has many costs. Mother and father exhausted walking a crying and hungry baby at night for one… Because you can’t give baby anything but breastmilk and frankly the quality of milk from a tired mother doesn’t have the hindmilk quality that satisfies baby and prevents gas… (Cluster Feeding anyone?) That’s a pretty vicious cycle, that results in a more and more tired Mom. I just wish I had been able to give myself permission to have offered baby a bottle of formula and gotten us all some rest.

            I am thankful I’m not that dumb anymore and am formula feeding my twin daughters without any fear! Nobody’s exhausted here. I think that’s wonderfully
            *freeing*, good and healthy for us.

          • Who?
            March 22, 2015 at 9:46 pm #

            I prefer people please themselves and have sufficient respect for others to mind their own business when others please themselves.

            Back in the day babies died or were malnourished when their mothers couldn’t feed them enough.

            And-this is interesting to me-many young women now will have been vaccinated as children. Anti-vax people-I don’t know if you’re one, but you might have a view on this-will say that vaccinated people who don’t get the illnesses lose their immunity over time, and that those who get the wild illness don’t.

            If this were so, then anti-vaxxers would not call on antibodies as a primary reason for breastfeeding if the mother was vaccinated.

            Are you (or anyone) aware if this is the anti-vax position?

          • KeeperOfTheBooks
            March 22, 2015 at 11:24 pm #

            How is it better for a child to have a mother who is so physically exhausted that she drops the kid?
            Because back when I was breastfeeding, I was so tired from never sleeping more than an hour and a half or so at a time that I more than once fell asleep sitting straight up and holding DD in front of me. Thank God I caught her before she hit the floor. Likewise, thank God for formula. If I had to deal with that kind of sleep deprivation much longer, I’m not sure that either one of us would be here. Wanting sufficient sleep to function isn’t selfish. Sleep, and enough of it, is a basic human physiological need. Long-term sleep deprivation can do terrible, terrible things to one’s psychological and physical health.

          • Staceyjw
            March 24, 2015 at 5:44 am #

            It’s worth it to spend $ on making formula better, because the fact is that most babies will eat some, at some point, even BF ones!
            It is that simple.

            “The most natural and healthy thing in life”
            You lost me with this. Which was fine because you went downhill from there.

            It’s not a mystery why so few moms BF, and fewer do exclusively, and in 2015 it’s not formula advertising. I’m sure there are some moms that would rather BF, and got shitty advice, but that has zero to do with improving the food that most babies eat at some point (formula). FEW babies are BF exclusively for any length of time, and in the US economics plays a much bigger role than bad advice. I also suspect some of the “well, I didn’t have enough milk” is an excuse given to people like yourself, so that a mom isn’t shamed by lactivists (who seem to LOVE to shame moms).

            Also, Please realize that Bf IS NOT a wonderful experience and relationship for every mom and baby. While me and my DD love BF so much she is only now weaning at 3, it was a no go with my son. It simply doesn’t work out well for so many, and even fewer have the *privilege* of being able to BF long term (let alone exclusively).

          • Spiderpigmom
            March 24, 2015 at 12:48 pm #

            “physiological impairments to breastfeeding are very rare”: insufficient supply is extremely common with women with PCOS, and PCOS itself is very common. To cite just one possible cause.

    • fiftyfifty1
      March 22, 2015 at 12:32 pm #

      I agree that I am sick of infant feeding choices being viewed through the lens of “mother sacrificing to create a better product”. No 2 infants are alike. No 2 mothers are alike. No 2 social situations are alike. We know from studies such as the discordant sib studies and the randomized PROBIT study, that there is little if any difference in outcomes between breast and formula when confounders are eliminated. So why not tell women that and let them freely choose the secondary benefits that might apply specifically to them:

      Cost: for some breast will be more economical, for others formula.

      Bonding: some may find a special closeness in breastfeeding, others will obtain that same closeness through bottle feeding.

      Illnesses: Perhaps your child is a preemie and might reduce NEC with breastmilk. Perhaps your child has a metabolic or allergy problem and thrives best on a special formula.

      Fertility: some may want an immediate return of fertility, others who don’t want to use birth control may enjoy the reduction in fertility that can come from breastfeeding.

      Convenience: for some this will be breast, others bottle

      Supply: Some struggle to produce enough breastmilk. Others live in a remote location where formula or clean water are not always in supply.

      Health benefits to mother: Maybe a woman wants to breastfeed to slightly decrease her risk of breastcancer. Other women may want to formula feed because they need to be on a medication that is risky for a breastfed baby.

      Personal preference: enough said

  11. Kazia
    March 19, 2015 at 9:08 pm #

    You know what else makes babies smarter? Talking to them.

    • gingergirl
      March 21, 2015 at 5:04 pm #

      Every time.

      • Amazed
        March 22, 2015 at 2:46 pm #

        I’d like to think that whatever additional “smartness” my mom gave me didn’t come from breastfeeding but all those nights when she was woken up by a fully alert toddler who insisted, “Don’t sleep! Read!” and she actually got up and started reading Thumbelina for the 1367835th time. (My dad found a way out of it by sleeping on his functioning ear, unless Mom was so wiped out (not from liquor!) that she poked him quite roughly to get him on reading duty. He compensated in the evening, though.)

  12. fiftyfifty1
    March 19, 2015 at 5:34 pm #


    The Belarus PROBIT study only showed a higher score on the verbal subtest, which does not, in my opinion, supprt the idea that there is a higher IQ score overall. Overall IQ and Performance IQ were not statistically different. If there really were a nutritional difference that caused improved brain development, it should show itself in multiple realms.

    I find it concerning that the PROBIT study shows very, very little in the way of concrete benefit of breastfeeding (in a nation with clean water and access to commercial formula)…but that the media and even the *researchers themselves* go out of their way to try to spin it as if it does. You can see the bias even in the opening lines of the report where they explain why they did the study:

    “The evidence that breastfeeding improves cognitive development is based almost entirely on observational studies and is thus prone to confounding by subtle behavioral differences in the breastfeeding mother’s behavior or her interaction with the infant.”

    Prone to confounding by subtle behavioral differences in the breastfeeding mother’s behavior or her interaction with the infant??!!! Hello, how about prone to confounding from every damn thing under the sun from parent’s IQs, to income, to the healthy adherer effect !!??
    Basically this opening statement shows that they have already closed their minds to the idea that breastfeeding might not raise IQ at alI. They have already jumped to the conclusion that it MUST, and are just trying to prove whether it is the milk itself or some magically enriching behavioral change that breastfeeding causes mothers to make. Their disappointment that they got a whole lot of not much from the results is palpable.

  13. mostlyclueless
    March 19, 2015 at 4:53 pm #

    One more comment on this — would be helpful to see effect sizes to illustrate the point you (Dr. A) are making here mathematically. If means and SDs are all reported in the manuscript it would not be hard. I would do it myself if I were not so swamped today 🙁

  14. Trixie
    March 19, 2015 at 3:47 pm #

    What types of breast milk substitutes were poor infants in Brazil in 1983 getting? I’m guessing not very good ones. Might that not also have an effect?

    • Trixie
      March 19, 2015 at 3:48 pm #

      Sorry, I see someone else already made this point below.

    • Mariana
      March 20, 2015 at 4:40 pm #

      Regular cow’s milk, usually thickened with maize or rice flour, very ripe bananas (true!), or nursed by another woman. This is what happened to my husband and his sisters, my mother in law had no milk.

      • Trixie
        March 20, 2015 at 11:39 pm #

        Yeah, so that could account for it, right there.

  15. mostlyclueless
    March 19, 2015 at 2:34 pm #

    If I understand these data correctly, breastfeeding 6-12 months increases IQ, but breastfeeding longer than 12 months has no effect / decreases IQ?

    Wonder if we’ll be seeing that on any lactivist blogs…

    • Mac Sherbert
      March 19, 2015 at 2:35 pm #

      I wonder, if that’s because the poor mom’s breastfeed longer???

      • Cobalt
        March 19, 2015 at 3:26 pm #

        Or extended loss of income. Not poverty causing breastfeeding but breastfeeding contributing to poverty.

        • Mac Sherbert
          March 19, 2015 at 3:30 pm #

          Either way would explain it. I was thinking a mom in poverty that is already breastfeeding might continue to bf past 6-12 months to avoid to buying milk/formula.

          • Mishimoo
            March 19, 2015 at 6:17 pm #

            I know that I wanted to breastfeed to a year, simply to save money on buying formula, and we’re financially stable. I imagine that the savings (not counting food for mum and opportunity cost) would be even more important to a stay-at-home-mum in poverty because it’s “free”.

          • Cobalt
            March 20, 2015 at 10:55 pm #

            I do it for the money. Thirty to forty bucks a week I don’t spend on formula, the time costs are the same (or less), and after the first 10 weeks it’s less work. I’m with the baby the same amount of time either way, and we have an uncomplicated nursing relationship, biologically speaking. The downside is the “touched out” feeling I get sometimes, but I’m willing to deal with that for the financial benefit.

    • fiftyfifty1
      March 19, 2015 at 4:13 pm #

      And this is not at all a new finding. Other studies have shown the same effect, where the longer you breastfeed past a year, the further and further IQ goes down.
      Do I think this effect is real, that somehow breast milk poisons your brain past 12 months? Of course not. But I also don’t believe that breastmilk boosts your intellect either. It’s all residual confounding. Actually patterns like this with no plausible biological mechanism are the *hallmark* of confounding.

  16. Cartman36
    March 19, 2015 at 1:27 pm #

    Having a high IQ doesn’t necessarily translate to success in life. Plus 3.7 points on an IQ scale isn’t really a big difference.

  17. DaisyGrrl
    March 19, 2015 at 12:55 pm #

    “Breastfeeding a baby who isn’t getting enough to eat may actually be far worse than not breastfeeding at all.”

    THIS should be on the walls of every BFHI hospital’s break room, on every breastfeeding pamphlet, etc. With the intense pressure to breastfeed, I feel like many public health officials are forgetting rule #1: FEED THE BABY!

    • threefoldgoddess
      March 19, 2015 at 2:04 pm #

      This! I had to bring formula to my admin assistant stuck in a BFH when her breastfeeding wasn’t working and they would not give her formula. Her baby has been screaming for SIX HOURS and the nurses and LCs refused. BTW, my admin assistant has been up for over 48 hours at this point. She called me in hysterics and I told her I would take care of everything. Bought a couple of RTF bottles and told the nurses they would keep bringing them to her and I was not leaving the hospital while she was there, because I could not trust she’d get the proper care. And I sat in that waiting room and kept checking on her. The nurses kept trying s*** but my glares kept them from saying a word and kept getting bottles for her.

      Took a week for her milk to come in, and she EBF for six months (our company gave three months paid maternity then the 3 months for the federal leave) and then pumped/BF until 18 months. That week of formula gave her a great breastfeeding relationship.

      BTW, we filed grievances everywhere we could and did get some interesting letters back about how they were supposedly going to change policies. I’ll believe it when I see it. What they did was obviously child abuse by letting a newborn starve.

      • moto_librarian
        March 19, 2015 at 2:14 pm #

        Thank you for filing grievances! This madness has to stop.

      • Kelly
        March 19, 2015 at 2:17 pm #

        Crying for six hours because the baby is hungry is ok but when they decide to sleep train at four months or older, it is child abuse? Six hours is a long time. That poor baby.

        • Cobalt
          March 19, 2015 at 2:26 pm #

          Sleep training is”convenient” for the mother, and if it’s convenient for the mother, it must be catastrophically and irreparably harmful for the baby.

        • ERnurse
          March 19, 2015 at 3:38 pm #

          Yes, havent you heard? The best mothers are the most miserable ones! This is why if you refuse to sleep train at the expense of the whole family, you win the best-mom-award.

          • Kelly
            March 19, 2015 at 3:49 pm #

            I was reading a blog about something else and they all were trying to get advice on getting their kids to sleep. This one lady spent two and a half hours every night getting her one year old to sleep. That is insanity.

          • ERnurse
            March 19, 2015 at 3:50 pm #

            That is insane. Sleep deprivation has a negative impact on babies too, not just parents!

          • Kelly
            March 19, 2015 at 3:58 pm #

            They just can’t see what they are doing to the child or themselves. This is “gentle parenting.”

          • Amy M
            March 19, 2015 at 8:22 pm #

            It’s all fun and games, until one of them “gently” falls asleep behind the wheel and drives into a tree. This makes me nuts, because sleep deprivation is not taken very seriously in the US at least, and it should be. It’s a real thing, and it has serious consequences.

          • theadequatemother
            March 20, 2015 at 7:43 pm #

            there was a study of the reaction time of resident physicians after a night of call (no sleep) and their reaction times were the equivalent of the drunk. Driving tired = driving drunk.

          • araikwao
            March 20, 2015 at 5:51 am #

            Ugh. There’s an awful, guilt-inducing (to me, at least) pic out there on the internet that tells you what wonderful neurological development happens at various time points during uninterrupted sleep. What research it is based on I have no idea, probably some sanctimommy made it up, but my crappily-sleeping kids would be needing intensive early intervention if it were true. Somehow, they are both super-bright little buttons. Must be the breastmilk 😛

          • ERnurse
            March 20, 2015 at 6:21 am #

            I’m not a fan of the mom-guilting in any form. In the current attachment-parenting trend, I have often seen the guilt go the opposite way- moms who sleep-train their babies in an effort for everyone to get more sleep are told that they are causing ” permanent psychological damage” by doing so, even if they only let them cry for 2 minutes, and instead they must continue to go just “deal with” crazy sleep schedules that leave the whole family sleep-deprived. Of course, some babies don’t sleep well no matter what you try and it’s not always in your control… Sanctimommies are crappy no matter which side they are on.

          • Allie P
            March 20, 2015 at 4:58 pm #

            My sleep trained, combo fed, crib-dwelling, nanny having baby is four, and currently cuddled next to me right now, eating apples and reading half the small words on the screen. I even put her in a GASP stroller sometimes. According to attachment parenting tenets she should be a stupid serial killer. Spend time with your kids, make sure they are adequately nourished and well looked after by you and their other caretakers, and you’re doing great.

          • araikwao
            March 22, 2015 at 5:04 pm #

            Yes, I agree it typically goes the other way, but I know when I was trying and trying to get my babies to sleep and I saw that infographic, I just had to close it, because it was something else to beat myself up over.

        • threefoldgoddess
          March 19, 2015 at 3:47 pm #

          Yeah, and a NEWBORN at that. Apparently baby started crying less than an hour after birth. I just hope there was no lasting damage. He is an adorable, giggly two year old now so I guess he wasn’t irreparably scarred.

          • Kelly
            March 19, 2015 at 4:12 pm #

            I am sure he is fine because she got help.

      • Mac Sherbert
        March 19, 2015 at 2:32 pm #

        That’s terrible, but yeah for you helping her! The hospital I gave birth in has recently said it’s going to try to obtain Baby Friendly status. 🙁

        My nurses were great and when I asked for formula they brought it without ever questioning why I wanted it. The LC later came in and told me to keep supplementing until the breastfeeding was working because the baby was starting to lose too much weight and her bili levels were a little high. It’s just horrible to think it could go from supportive to what your friend experienced once they go baby friendly. Maybe I should write a letter in protest of them going baby friendly.

        • Cartman36
          March 19, 2015 at 3:38 pm #

          I plan on finding the home number for the hospital legal counsel in case I have this issue for my next child.

        • threefoldgoddess
          March 19, 2015 at 3:45 pm #

          The sad thing was that on her maternity tour, they told her that they supported mothers choosing what worked best for them. She even had a pamphlet that said this. Then they did that to her. I’m just glad she thought to call me. While I’m her boss, we have a great working relationship that is like a friendship and she has no family anywhere nearby. It my job to protect her from people harassing her at work, so it was natural for me to do it at the hospital. In fact, it was quite pleasurable to see those power-hungry nurses and LCs squirm and look away as I laid down the new ground rules 😉

        • rh1985
          March 19, 2015 at 8:14 pm #

          it’s sad but it almost seems like the only way to guarantee you’ll get formula is to say you won’t be BF at all, period.

        • Allie P
          March 20, 2015 at 4:51 pm #

          My hospital has also gone Baby friendly, and seeing as I plan to give birth there again, I’m not happy about what I’m hearing about these places.

      • Cartman36
        March 19, 2015 at 3:36 pm #

        One of the things people conveniently forget when talking about how “easy” breastfeeding is compared to formula is that not every working mother has a company that is willing to support her in breastfeeding. When I went back to work at 3 months, I had a private office with a lock, I purchased a small refrigerator to store milk, and I paid for a breast pump out of pocket. A lot of women work at places that don’t have these amenities or cannot afford them. .

        • threefoldgoddess
          March 19, 2015 at 3:41 pm #

          *nods* Our company is very cool for breastfeeding mothers. When my admin assistant came back, she had an office she could lock and still be able to do her work, so she didn’t have to cut into paid time. We also had a mini-fridge in there. But I know we are an outlier, not the norm.

        • KarenJJ
          March 19, 2015 at 7:31 pm #

          Yep. Breastfeeding mothers didn’t get access to a private office. One mum pumped in the disabled toilets. Breastfeeding didn’t work out for me so it became a moot point in the end in that I raised it but didn’t pursue it (I’d managed to negotiate two months of paid maternity leave for all the women at my company and decided not to push my luck any further).

        • rh1985
          March 19, 2015 at 8:12 pm #

          Also, some women just don’t respond to a pump. One of the moms from my new mom’s group at the doctor’s office had an easy time BF while on maternity leave. She had 3 months off then initially only worked half the week. So she had time to establish BF. She had a comfy place to pump. She just got almost nothing from the pump. An entire day of pumping, she’d be lucky enough to get enough for a single bottle. After a couple of weeks, she gave up and decided he’d have formula while she worked and she’d BF when she was home for as long as her supply lasted.

          • Medwife
            March 20, 2015 at 1:22 am #

            I’m trying to get a long distance friend to ease off pumping and nursing Q2hrs around the clock. She’s got a 3 week old and is desperate to increase her supply. It breaks my heart because she’s got this beautiful healthy baby, a sweet husband, supportive family, and she is driving herself straight towards rip roaring PPD out of exhaustion. She mists have so little time of simply cuddling with her baby. Same old story I keep reading here and seeing from time to time in my clinic.

          • March 20, 2015 at 3:43 am #

            Perhaps if you point out to her that the single biggest factor in producing an adequate milk supply is the avoidance of maternal exhaustion, she might be willing to ease up a bit.

  18. demodocus' spouse
    March 19, 2015 at 12:33 pm #

    I’m shocked, utterly shocked. Higher socio-economic status has more long-term advantages than being breastfed for a year?! (Note sarcasm)

  19. Mel
    March 19, 2015 at 12:22 pm #

    This reminds me of the studies that come out every so often about the effect that being a twin or triplet has on IQ.
    Since I’m a twin, I should be about 7 IQ points lower than I would be if I had been a singleton.
    I prefer having a twin to being marginally smarter.
    I’d prefer feeding a baby in a mutually satisfying way than struggling through months of semi-successful breast feeding to have a marginally smarter kid.

    • Amy M
      March 19, 2015 at 12:27 pm #

      Huh…how much of that is because a lot of twins are born prematurely? It’s pretty well known that prematurity can have negative impacts on neurological development.

      My twins seem to have similar intelligence to each other, and every evaluation they’ve had (school-wise) shows they are pretty bright, so I guess the formula wasn’t such a big deal. I don’t know what their IQs are, but I don’t really care either—they are learning to read and do math just fine, they love learning, and they are basically happy kids. That’s what is important.

      • Mel
        March 19, 2015 at 12:45 pm #

        Yeah, we’ve never worried about it. My sis and I were very premature, very sick unexpected twins 30-odd years ago and were mostly formula fed.

        We’re also very intelligent both in terms of tested IQ and lifetime achievements.
        So, yeah. Probabilities awesome at large scales. In terms of n=1 where you are n, it’s not so important.

        • The Bofa on the Sofa
          March 19, 2015 at 1:48 pm #

          Yeah, we’ve never worried about it.

          To be fair, there IS no reason to worry about it since there isn’t anything you can do about it.

          Even if it did affect your IQ, it’s not like you can fix it by going back and being full term and breastfed.

  20. Lemongrass
    March 19, 2015 at 12:22 pm #

    These people were also drinking formula from over 30 years ago…formula has come a long way since then! Indeed, didn’t the study author say he thought it was the DHA in breast milk that increased IQ? Well, lots of formula companies have started adding DHA to their formulas in the last few years.

    • The Bofa on the Sofa
      March 19, 2015 at 12:23 pm #

      That was my reaction as well. Well, if the key is all the long-chain saturated fats of breastmilk and that is what makes it better than formula, that’s easily remedied.

      • Guesteleh
        March 19, 2015 at 1:43 pm #

        My son was born eight years ago and Costco was already adding DHA to their budget, loved-it-so-much formula. Will be interesting to see IQ results in future BF studies.

    • AllieFoyle
      March 19, 2015 at 12:50 pm #

      Good point.

    • Mac Sherbert
      March 19, 2015 at 2:03 pm #

      I’ve asked a similar question before in connection to another study on Breastfeeding and IQ. I seem to remember someone posting that DHA was in formula in Europe (and maybe other countries) long before it was added to formula in the US????

  21. alannah
    March 19, 2015 at 12:06 pm #

    It would be interesting to see a comparison between FF and BF with an ‘intention to treat’ analysis.

    That means that women who attempt BF but are unsuccesful stay in the BF group so that the impact on IQ of dehydration/starvation/failure to thrive from unsuccessful attempts at BF doesn’t end up in the FF group.

    Such a study would also reveal the true incidence of lactation failure in a population of mothers who choose to BF. I have a sneaking suspicion it’ll be much higher than the 3% the lactivists keep citing.

    A pity that this kind of study will only get funded when pigs sprout wings.

    Also, does anyone in this excellent group of commenters know what kind of formula was available to low SES women in Brasil in the early 1980s?

    • Cobalt
      March 19, 2015 at 12:10 pm #

      First, excellent point on the intent to treat angle.

      Second, not only formula availability, but also preparation. If you’re poor and “stretching” formula with extra water or adding other inappropriate foods to fend off starvation, malnutrition is likely.

    • Mel
      March 19, 2015 at 12:25 pm #

      In dairy cows, primary lactation failure is around 8-10%. Secondary failure varies by age of dam.

      Remember, though, that dairy cows are MUCH more strongly selected for milk production than humans are and so the rates may well be LOWER than in humans.
      To quote my husband: “It doesn’t seem right that we know more about lactation failure in cows than we do in humans…..”

      • Cobalt
        March 19, 2015 at 12:42 pm #

        Lactation failure in cows is more important economically than lactation failure in humans, at least in developed nations. Cow’s milk feeds more people at any given time than breastmilk does, and more cheaply.

      • Guesteleh
        March 19, 2015 at 1:42 pm #

        I love your cow posts. Always super informative and interesting.

      • Sarah1035
        March 19, 2015 at 2:11 pm #

        I wonder if you shamed and humiliated the cows that weren’t producing enough if they would give more milk, seems to work in humans.

        • Cobalt
          March 19, 2015 at 2:32 pm #

          If the threat of burgerdom doesn’t work, I don’t know what will.

      • Mac Sherbert
        March 19, 2015 at 6:16 pm #

        Speaking of cows…Saw this today. If it was a human, I’m sure the breastfeeding advocates would insist this cow is able to nurse all four calves instead of having 3 of them sent to the neighbors.

    • Roadstergal
      March 19, 2015 at 2:50 pm #

      “the impact on IQ of dehydration/starvation/failure to thrive from unsuccessful attempts at BF doesn’t end up in the FF group.”

      That’s a very good point. Babies that are starved to the point of hospital admission from unsuccessful BF end up in the FF cohort, just as homebirth trainwrecks end up on the OB’s statistics.

  22. Amy M
    March 19, 2015 at 12:04 pm #

    I am under the impression that IQ isn’t static either (as in your IQ score that you get at 10 can be different at 20). Not only might testing the same person on different days lead to variable scores, but in terms of lifestyle. For example, I think I read that exercise and playing musical instruments are all beneficial for brain development. Could that sort of thing affect IQ as well? If so, I would think it would have a greater impact than what a baby ate for the first 6mos-1yr, because people can exercise and play music their whole lives.

  23. Cassandra Rose Leathem
    March 19, 2015 at 11:53 am #

    Thank you! I just saw this study and read through the summary in the lancet, your page was my first stop after that. I appreciate that you take it piece by piece so that all of the factors are laid out clearly. I shared it in my breastfeeding groups, we’ll see how many rants and crunchy crazies I get personal attacks from. (I am breastfeeding by the way, because I am lucky enough to have the privilege to stay home with my little one)

    • Guesteleh
      March 19, 2015 at 1:40 pm #

      Your profile pic is absolutely adorable.

  24. jhr
    March 19, 2015 at 11:51 am #

    Since normal neurological development is severely compromised by starvation, making sure that the infant is receiving adequate nutrition is the only gold standard here.

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