Breastfeeding gives IQ boost, for some

Many people claim that breastfeeding makes babies brainy. And yes, the evidence suggests it does -- but only if the baby carries the right gene.

Terrie Moffitt from King's College London and her colleagues analyzed the DNA of two groups of people, 1,000 born in New Zealand during the 1970s, and 2,200 born in the United Kingdom during the 1990s. They were looking for variations in a gene called FADS2, which makes an enzyme involved in fatty acid metabolism. Participants were also asked whether they'd been breastfed.

The 10 percent of participants who carried a less common variant of the gene scored similarly in IQ tests, regardless of whether they had been breastfed or not. By contrast, of the 90 percent of people carrying a more common form of the gene, those who were bottle-fed scored on average 6.8 points lower in IQ tests than those who were breast-fed. The mother's genotype, IQ or social class did not affect the result.

Fatty acids contained in breast milk are thought to be important for brain development, and the more common variant of FADS2 processes these fatty acids more efficiently. Moffitt believes this could explain the differences in IQ, although larger studies are needed to confirm it.