In 2001, Michael Kramer of McGill University began publishing his research about the Promotion of Breastfeeding Intervention Trial, or PROBIT, which evaluated breast-feeding's effects on 17,000 Belarusian children. Rather than telling a woman how to feed her children, Kramer used women who began breast-feeding at birth. Half of the mothers, though, were encouraged to breast-feed exclusively for much longer by a health professional, while the other half received no such intervention. The women who received more information breast-fed their babies for much longer, allowing researchers to study extended exposure to breast milk.
So far, Kramer's research has shown that breast-feeding is a little bit better than formula-feeding, but it's not the universal panacea that its supporters claim. Extended breast-feeding can reduce the risk of eczema, and it can also reduce the risk of gastrointestinal infection during the first year of life by 40 percent [sources: Rosin; Kramer et al.]. Perhaps most notably, Kramer found that breast-fed babies scored higher on IQ tests; these children scored 7.5 points higher on tests measuring verbal intelligence and 2.9 points higher on tests measuring non-verbal intelligence at the age of 6 and a half [source: Doheny]. Despite the excitement this news generated in parenting circles, Kramer called the effects "modest," pointing out that 7.5 points was "not the difference between a genius and a mentally retarded child" [source: Doheny].
Kramer has suggested that breast-feeding's benefits may not come from the breast milk, but rather from the time mothers spend interacting closely with their child. When Hanna Rosin of "The Atlantic" spoke to Kramer, he talked about how rats lick and groom their pups, suggesting that it's the physical act of breastfeeding, as opposed to the breast milk itself, that gives children a leg up in the world. Such a distinction is important, because many women in the United States pump their breast milk and feed it to their children via a bottle. Are these women wasting their time?