Both the Kramer study and the sibling study did turn up one interesting finding: a bump in “cognitive ability” among breast-fed children. But intelligence is tricky to measure, because it’s subjective and affected by so many factors. Other recent studies, particularly those that have factored out the mother’s IQ, have found no difference at all between breast-fed and formula-fed babies. In Kramer’s study, the mean scores varied widely and mysteriously from clinic to clinic. What’s more, the connection he found “could be banal,” he told me—simply the result of “breast-feeding mothers’ interacting more with their babies, rather than of anything in the milk.”

The IQ studies run into the central problem of breast-feeding research: it is impossible to separate a mother’s decision to breast-feed—and everything that goes along with it—from the breast-feeding itself. Even sibling studies can’t get around this problem. With her first child, for instance, a mother may be extra cautious, keeping the neighbor’s germy brats away and slapping the nurse who gives out the free formula sample. By her third child, she may no longer breast-feed—giving researchers the sibling comparison that they crave—but many other things may have changed as well. Maybe she is now using day care, exposing the baby to more illnesses. Surely she is not noticing that kid No.2 has the baby’s pacifier in his mouth, or that the cat is sleeping in the crib (trust me on this one). She is also not staring lovingly into the baby’s eyes all day, singing songs, reading book after infant book, because she has to make sure that the other two kids are not drowning each other in the tub. On paper, the three siblings are equivalent, but their experiences are not.

What does all the evidence add up to? We have clear indications that breast-feeding helps prevent an extra incident of gastrointestinal illness in some kids—an unpleasant few days of diarrhea or vomiting, but rarely life-threatening in developed countries. We have murky correlations with a whole bunch of long-term conditions. The evidence on IQs is intriguing but not all that compelling, and at best suggests a small advantage, perhaps five points; an individual kid’s IQ score can vary that much from test to test or day to day. If a child is disadvantaged in other ways, this bump might make a difference. But for the kids in my playground set, the ones whose mothers obsess about breast-feeding, it gets lost in a wash of Baby Einstein videos, piano lessons, and the rest. And in any case, if a breast-feeding mother is miserable, or stressed out, or alienated by nursing, as many women are, if her marriage is under stress and breast-feeding is making things worse, surely that can have a greater effect on a kid’s future success than a few IQ points.

So overall, yes, breast is probably best. But not so much better that formula deserves the label of “public health menace,” alongside smoking. Given what we know so far, it seems reasonable to put breast-feeding’s health benefits on the plus side of the ledger and other things—modesty, independence, career, sanity—on the minus side, and then tally them up and make a decision. But in this risk-averse age of parenting, that’s not how it’s done.

* * *

In the early ’90s, a group of researchers got together to revise the American Academy of Pediatrics’ policy statement on breast-feeding. They were of the generation that had fought the formula wars, and had lived through the days when maternity wards automatically gave women hormone shots to stop the flow of breast milk. The academy had long encouraged mothers to make “every effort” to nurse their newborns, but the researchers felt the medical evidence justified a stronger statement. Released in 1997, the new policy recommended exclusive breast-feeding for six months, followed by six more months of partial breast-feeding, supplemented with other foods. The National Organization for Women complained that this would tax working mothers, but to no avail. “The fact that the major pediatric group in the country was taking a definitive stance made all the difference,” recalls Lawrence Gartner, a pediatrician and neonatologist at the University of Chicago, and the head of the committee that made the change. “After that, every major organization turned the corner, and the popular media changed radically.”