Study: Breast-Fed Babies Grow Up Smarter

If you breast-feed, your baby might grow up to be a smarter adult, according to a new study.

How long a baby is breast-fed may be associated with the child's intelligence level later in life, according to an article in the May 8 issue of the Journal of the American Medical Association.

Erik Lykke Mortensen from Copenhagen University Hospital in Denmark and June Machover Reinisch from the Kinsey Institute for Research in Sex, Gender and Reproduction at Indiana University in Bloomington, Ind., studied the relationship between duration of breast-feeding and intelligence in young adults.

A number of studies suggest a positive association between breast-feeding and cognitive development in early and middle childhood. But other studies of childhood and adult intelligence show that intelligence is quite unstable during the first decade of life, it is possible that children who were bottle-fed may catch up and attain the same intelligence level of children who were breast-fed.

"Independent of a wide range of possible confounding factors, a significant positive association between duration of breast-feeding and intelligence was observed in two independent samples of young adults, assessed with two different intelligence tests," the authors wrote. They found that IQ levels rose the longer the person had been breast-fed as a child, with six months of breast-feeding representing the peak of intelligence.

The researchers said that their findings suggest that there are no additional positive effects of breast-feeding after nine months.

Researchers aren't sure why the association exists between breast-feeding and intelligence.

They said that breast milk may contain nutrients not found in cow's milk or formula that stimulate brain development, which the leads to greater intelligence. They also suggested that the physical and psychological contact between mother and child during feedings contributes to later intelligence.