Breast-feeding has been linked--often effusively--to more smarts. In fact, a stack of medical studies in recent years has led many parents to believe that breast-feeding is a must if they want their children to do well in school.
Such conclusions may have been a bit hasty. The latest study on the effects of breast-feeding suggests that many of the earlier studies don't make the grade when it comes to good scientific research.
A paper in the June issue of Pediatrics analyzed 40 studies on the link between breast-feeding and cognitive development, 68% of which concluded that breast-feeding promotes intelligence. The studies showed, among other things, that breast-fed babies score higher on cognitive tests, get better grades in school and have higher IQs as adults than babies who were bottle-fed. Some found that intelligence increases for each additional month that a baby is breast-fed.
But researchers from Yale University and the University of Chicago say their analysis shows that most of the studies had serious flaws. Only two, in fact, met all the authors' criteria for quality research; one of those found a "significant" effect of breast-feeding on intelligence; the other found no correlation.
"The studies have not been very good--and there have been a lot of them," says Dr. Anjali Jain, who co-wrote the analysis. One major problem with the studies, she says, is they often didn't take into account the importance of factors besides breast milk. Some of those factors may be responsible for the intelligence gains. "Breast-feeding itself takes a fair amount of motivation," she says. "Just being a motivated parent is important. But a bottle-fed child could also be [cognitively] stimulated by a motivated mother."
Another flaw with much of the research was that it failed to accurately measure how much breast-feeding took place, such as by recording the amount of time spent breast-feeding or whether the baby also received formula, Jain says.
However, other experts say the evidence for a connection between breast-feeding and intelligence is still persuasive.
Good breast-feeding studies are difficult to do because researchers "can't tell one mother to breast-feed and another she cannot" for purposes of their study, says Dr. Ruth Lawrence, a breast-feeding expert at the University of Rochester School of Medicine. But that doesn't mean health experts should disregard a preponderance of evidence showing a link, she says.
