YES says Betty Vohr, M.D., professor of pediatrics at Brown University and director of the neo-natal follow-up clinic at Women & Infants Hospital of Rhode Island in Providence. I'm a firm believer that breast milk makes babies smarter, and a study I co-authored helps prove this. Much research has already shown the beneficial effects of breast milk on mental development in normal-weight babies; we decided to study the effects in high-risk, extremely low-birth-weight babies (2 pounds, 3 ounces or less at birth). We followed 1,035 of them from birth through 18 months, at which time we studied their mental development.
During each infant's months-long stay in the hospital, we recorded his total daily nutritional intake, including IV fluids, formula or breast milk. We then controlled for factors known to affect mental development, including the mother's age, educational level, marital status and ethnicity, plus medical complications in the infant. We observed significant improvements in the babies who received breast milk: For every 1/3 ounce per 2.2 pounds of body weight per-day increase in breast milk intake, the child's mental index increased by 0.53 points, which equates to a half-point gain in IQ. Babies who received the most breast milk showed the most gain in IQ: 5.3 points.
Whether babies are born full term and at normal weight, or premature and at extremely low weight, increased amounts of breast milk raise a child's IQ. The benefit is likely due to long-chain polyunsaturated fatty acids found in breast milk.
NO says Geoff Der, M.Sc., a statistician with the Social and Public Health Sciences Unit of the Medical Research Council in Glasgow, Scotland. While I agree that breast milk has untold benefits for mothers and their babies, I'm fairly comfortable saying that increased IQ isn't one of them. In a recent study, we looked at more than 5,000 children born to 3,000 mothers and compared those who were breastfed with those who weren't. We found that the children who were breastfed did better on tests of mental development than those who weren't--they scored about 4.5 IQ points higher. But when we took into account the mother's IQ, 70 percent to 75 percent of that advantage disappeared.
We then looked at a few more factors, such as the mother's education and age, as well as the amount of stimulation the child received in the home and whether the family income was above the poverty line. When we took these factors into account, the advantage for the breastfed children pretty much disappeared--down to half an I.Q. point or less.
To test our theory that family background has more impact than breast milk on a child's IQ, we then studied 332 pairs of siblings in which one was breastfed and the other wasn't. Again, there was very little difference. An important caveat: Our study was conducted in developed countries and with full-term babies of normal birth weight. Things may be different in the developing world or for premature and low-birth-weight children.