Benefits of breast-feeding on child's intelligence questioned. (Evidence from Metaanalysis Scrutinized).

The evidence that breast-feeding benefits a child's intelligence remains unconvincing, according to Dr. Anjali Jain of the University of Chicago Children's Hospital and colleagues.

In a metaanalysis of 40 published, English-language studies on the association between breast-feeding and cognitive outcomes, 26 (65%) concluded that breast-feeding promotes intelligence. However, only two studies met all of the investigators' requirements for a high-quality study. One concluded that breast-feeding was associated significantly with higher intelligence, but the other found no such association (Pediatrics 109[6]:1044-53, 2002).

Half of the 14 studies that showed no association between breast-feeding and intelligence did show a statistically significant relationship before the results were adjusted for confounding variables.

Outside of the two high-quality studies, only three of the seven studies in the metaanalysis that controlled for the crucial confounders of socioeconomic status and child stimulation concluded that breast-feeding promotes intelligence.

The investigators defined high-quality studies as those that sufficiently defined breast-feeding, followed full-term infants longitudinally, controlled for socioeconomic status and child stimulation, reported an interpretation of the breast-feeding effect between groups, and measured intelligence by age 2 or later with a standardized instrument by blinded observers.

Dr. Ruth Lawrence, a member of the American Academy of Pediatrics' newly established Provisional Section on Breast-Feeding Executive Committee, said during an interview that the investigators did a good job of applying their criteria for quality studies.

But she called the results ...