Breast-feeding has little or no effect on children's later intelligence, according to the largest study ever to address this question.
The influence of breast-feeding on cognitive ability has been debated for more than 70 years, with multiple potentially confounding factors having been identified. These include socioeconomic status, birth weight, maternal history of smoking, maternal and paternal education, and race or ethnicity. Maternal intelligence, however, has largely been overlooked as a potential confounder in studies investigating the effects of breast-feeding, according to Geoff Der, a statistician at the Medical Research Council's Social and Public Health Sciences Unit in Glasgow, Scotland.
Analyzing data from 5,475 children and their mothers in the population-based U.S. national longitudinal survey of youth that began in 1979, Mr. Der and his colleagues found that if maternal intelligence was not included as a potential confounder, breast-feeding did appear to exert beneficial effects on children's intelligence, adding approximately 4 points. However, when maternal intelligence was included in the analysis, breast-feeding was associated with an increase of less than half a point (BMJ 2006 Oct. 4 [doi:10.1136/bmj.38978.699583.55]). Previous studies' not having considered maternal intelligence was “surprising given the heritability of intelligence,” he observed.
The researchers also determined that an increase of 15 points in maternal intelligence more than doubled the likelihood that the child would be breast-fed. They furthermore observed that mothers who breast-fed tended to be older and more educated, and to provide a more stimulating home environment.
Despite the lack of association with children's intelligence, breast-feeding remains important for overall growth and development, Mr. Der noted.