Of Brains and Breast Milk

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I called my mother last week to find out something only she would know: how long I was breast-fed. She remembered right away. "Three months," she said. "But I wish it had been longer." It turns out that my brother, who is 10 years younger, was breast-fed for seven months. Maybe, says my brother, that's why he's so much smarter than I am.

He's referring to an article in last week's Journal of the American Medical Association reporting that adults who as babies were breast-fed for seven to nine months had higher IQs than those who were breast-fed for two weeks or less. The study, conducted on 3,253 Danes born from 1959 to 1961, found that their scores on intelligence tests rose gradually the longer they had been breast-fed as babies. The average increase: about 6 points. (The average IQ is 100.)

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Of course, you don't need to be a genius to know that breast-feeding is good for babies. There is simply no better food for newborns. Breast-fed babies have lower rates of hospital admission, ear infection, diarrhea, rashes, allergies and other medical problems than bottle-fed tots. Another paper last week reported that breast-feeding protects against respiratory illnesses.

The debate over how long to breast-feed a child has probably been going on as long as children have been breast-fed. The American Academy of Pediatrics recommends that babies nurse for six months and, if possible, for 12 or more. (Iron-fortified infant formula can be substituted, if necessary, but no cow's milk for a full year.) Twelve months is a long time, however, especially for working mothers. I asked June Reinisch, former director of the Kinsey Institute and one of the authors of the J.A.M.A. study, what she advises. "More is better" as far as IQ is concerned, she says. "Up to nine months."

What is it about breast milk that makes babies so smart? Reinisch suspects there is a component of mother's milk that either protects the central nervous system or stimulates its development. The likeliest candidate: a long-chain polyunsaturated acid known as dha that is found in human milk but not in infant formula or cow's milk. Today's infant formulas, by the way, are fortified with a precursor of dha called ala and may offer some of the same benefits.

But there may be a subtler explanation for why breast-fed babies are smarter. Think of the duration of breast-feeding as a measure of the interest, time and energy that a mother is willing to invest in the child during the whole upbringing period. As the authors note, it may be that "mothers who spend more time breast-feeding during the first year of life also spend more time later interacting with the child."

Whatever the reason, the bottom line is the same. "If you can breast-feed, do it," says Reinisch. For the record, Reinisch is a very smart woman with a Ph.D., yet she was never breast-fed. I was breast-fed only briefly, and while I think I probably could have used a few extra IQ points, my mother assures me that I turned out just fine.

Thanks, Mom. And again, happy Mother's Day.

Dr. Gupta is a neurosurgeon and cnn medical correspondent