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The Breast and the BrightestDoes nursing really affect your kid's IQ?

By Emily Bazelon
Posted Thursday, Nov. 8, 2007, at 5:47 PM ET

(Continued from page 1)

Previous studies have also linked breast-feeding to higher IQ, but they generally haven't ruled out the fact that breast-fed kids are also more likely to come from wealthier and better-educated families than formula-fed babies. What has looked like a correlation between nursing and smarts might really have been explained by other more predictable factors. Caspi and Moffitt, however, controlled for the confounding factors of social class and maternal IQ. And they still found a pattern of higher IQs in the breast-fed babies with the C alleles. Nor did the advantage seem related to the mothers' genotypes.

Caspi and Moffitt point out that in the earlier annals of human history, when everyone was breast-fed, "genetic variation in FADS2 could have influenced individual differences in intelligence." In this sense, they say, "It is reasonable to ask whether FADS2 is a 'gene for' IQ." Maybe that helps explain why 90 percent of the population has the C allele—if it promotes intelligence, then it should win out in the process of natural selection. From a pro-breast-feeding point of view, this is all kind of lovely. Some babies have a gene that boosts intelligence, but only when it's activated by the delivery of mother's milk, and so, over time, more babies have the gene. Nature and nurture working in tandem, and to a good end.

OK, enough with the cave folk. What about us? Breast-feeding helps make most kids smarter, if the results of this study bear out in future research. In a birth order study that came out earlier this year, much was made of a three-point IQ edge for firstborns, so the nearly seven-point jump associated with breast-feeding and the C allele looks substantial. But the nursing doesn't help all kids—and so it's actually one more source of heightened inequity. Not just in the sense that kids who aren't breast-fed don't get the boost, a "shame-on-mothers" argument we're used to. No, now we have to add on a genetically based inequity. Of course, life is full of those, but they're still discomfiting, and perhaps all the more so in the presence of this sort of G × E interaction. There are two ways to lose out, genetic and experience-based. And to win, you need both to go your way. (We're talking about averages over populations, not one-to-one correlations, of course, but you can still see the point.)

Then there's the question of genetic testing. You could test a child for the C allele, and if she has it, feel even better about nursing her. You'd also feel worse if you can't. And if your baby is in the 10 percent without the lucky gene variant? You can still nurse, of course, but your rationale would be different—and wouldn't you feel ripped off by nature's grand lottery, and a little bitter about it, at least on a sore-nipple day?

This is the kind of information we may not really want to have. The sinisterish ramifications are even starker in other research that Caspi and Moffitt have done, in which they've found a G × E relationship for a gene that's linked to depression in connection with an experience of serious trauma, like child abuse. Do we want to know who has this predisposition? (A test already exists.) If you were thinking about adopting a child who might have had some hard experiences, wouldn't you choose the child with the protective variant of the gene over the one without it? And what does that mean for the genetically unblessed kid? If you ran an adoption agency, would you give kids the test? Questions for the near future, or, really, for now.

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Emily Bazelon is a Slate senior editor.
Illustration by Robert Neubecker.
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Remarks from the Fray Editor:

As with anything touching on the benefits of breast feeding, Emily Bazelon's article has brought out articulate champions from both sides of the breast-feeding wars. Jheurf relates a harrowing tale of watching his infant's health take a second seat to the cause of promoting breast feeding among new mothers. On the other side of the debate, Sarvis compares the preference for formula feeding to a "voluntary colostomy" movement. Other excellent posts are excerpted below. –G.A.

Remarks from the Fray:

It's not that I think mothers who can't breastfeed are not as good as mothers who can. It's that I think mothers who don't but could ought to at least take the trouble to educate themselves about it, and to give their children at least a few weeks of the one meal you don't have to prepare in a busy day.

I wonder how much of women's reluctance to breastfeed when they are able has to do with the actual difficulty involved, and how much has to do with fear. Fear of saggy boobs leading to sexual rejection, fear of being castigated for displaying boobs, fear of being the sole supplier of meals for another human being, especially at 4 am, fear of bodily fluids, fear of being overwhelmed, fear of being a mammal, fear of men's fear about women's bodies and power, fear of the general public's fear of boobs.

As long as someone's out there lying to women and saying that breast milk is no better than formula, so they can make a few more bucks, it's a lot easier to let your fears overcome every other consideration.

--Isonomist

(To reply, click here.)

I have never met a new mother that didn't have some type of difficulty early on. It is the rare mother and newborn combo that results in flawless breastfeeding right from the start. Yes, it's "natural" but so is walking and you have to struggle to learn how to do that as well. We do mothers a great disservice by telling them that the need to breastfeed, it's so important, etc but not providing support once they give birth.

It's little comments like these that make me wonder - is the author betraying a bias, showing that she really does think that all of the moms that cite difficulty as the reason that they don't breastfeed are full of it? Or am I being defensive and hypersensitive? Why, when it comes to our children are we so invested in what others think?

--gracep117

(To reply, click here.)

It was precisely studies of this kind that purported to show that hormone replacement therapy for post-menopausal women saved lives. Doctors were reassured that every conceivable confounding factor had been taken into account and "controlled for", with the final result being that hormone replacement was a great thing. Women who got hormone replacement in these studies DID live longer and get fewer diseases.

But when more rigorous studies were done, it turned out to be completely wrong. Hormone replacement therapy didn't save lives - it killed! The reason women who took it lived longer in those earlier studies was because they were DIFFERENT than the women who didn't in many other ways that had nothing to do with hormone replacement therapy, despite all the researchers' assurances that everything had been "controlled for".

As a result, a generation of women was exposed to needless risk based on faulty science, and thousands probably died. In my opinion, it is one of the great shames of modern medicine. It was exactly the same kind of study design that led to that tragic result, so think twice before believing stuff like this.

--mnemon

(To reply, click here.)

(11/12)

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