<Research on breast-feeding>

  A new study is adding more evidence to the connection between breast-feeding and intelligence. The study links intelligence in adults to how long they were fed their mother’s milk as a baby. It found that babies who were breast-fed for 9 months grew up to be more intelligent than those breast-fed for less than one month.

  Researchers at Copenhagen University Hospital in Denmark carried out the study. The Journal of the American Medical Association reported the findings. Other studies have examined the link between mother’s milk and intelligence in children.

  Organizers of the new study say theirs is the first to show a link between breast-feeding and adult intelligence. The organizers say their study also examined other considerations, such as a mother’s education and economic situation. The study involved more than 3,000 young Danish men and women. They were born in Copenhagen between 1959 and 1961. When the children were one year old, the mothers were asked how long they had breast-fed their babies.

  In the 1970s and 1980s, researchers used two tests to measure the intelligence of those children. One test was given to almost 2,300 men when they entered the Danish military. Their average age was 19. A different test was given to about 970 men and women. Their average age was 27. The Danish and American scientists found that babies who had been breast-fed for 9 months did better on the intelligence test as adults. Breast-feeding longer than 9 months had no additional effect on the test results.

  It is not clear why breast-fed babies may perform better in intelligence tests as adults. However, the scientists note that mothers’ milk contains substances not found in cow’s milk or milk products for babies. For example, breast milk contains two fatty acids that appear to support brain development. They are among hundreds of nutrients found in breast milk and not in other milk products.

  The scientists say the physical and emotional relationship between a mother and child that develops during breast-feeding also might be important. They say women who breast-feed their babies may spend more time with them.