Does Breastfeeding Boost IQ?
Study Shows Breastfed Kids Score Better on Some IQ Tests
Breastfeeding and IQ: Test Results
When the kids reached age 6 1/2, the children's pediatricians gave them intelligence tests. If they were in school, teachers evaluated their academic performance in reading, writing, math, and other subjects.
The strongest effect, Kramer says, was improvement in verbal IQ. On average, those in the intervention group scored 7.5 points higher on tests measuring verbal intelligence, such as vocabulary, which was statistically significant (meaning not due to chance). They scored 2.9 points higher on those tests measuring nonverbal intelligence and 5.9 points higher on tests measuring overall intelligence.
Kramer says the nonverbal and overall IQ test score differences were not statistically significant -- but just barely. He says the more important point is that he found an overall trend to improvement in the measures in the long-term or exclusively breastfed children.
Teachers rated the breastfed intervention group's reading and math better than the control group children.
"I think it's a modest effect," Kramer says. The IQ advantage for the long-term breastfed children, he says, is similar to what has been found in research for first borns vs. younger siblings.
"It's not the difference between a genius and a mentally retarded child," he says.
Breastfeeding and IQ: Breast Milk or Social Interaction?
Whether the boost in IQ is due to the breast milk itself -- such as healthy fatty acids or other substances -- or the physical and social interaction that is part and parcel of breastfeeding is unknown, Kramer and others say.
"A mother who breastfeeds is likely to spend more time with her child," he says, as well as read to them later and do other activities. "The amount of time, the closeness, the way she interacts with the kids, undoubtedly differs between breastfeeding and non-breastfeeding mothers."
The bulk of studies on the topic, he adds, have shown a positive link. One notable exception: a study published in 2006 in the British Medical Journal concluded that breastfeeding has "little or no effect on intelligence in children." The study involved more than 5,400 children.
Kramer says his study is sounder because of a more rigorous methodology.