Babies who are breastfed score better on intelligence tests down the road, according to a new study that suggests support for new moms could boost the brainpower of the next generation.
The study of more than 1,300 moms and their babies, who were breastfed for periods ranging from less than a month to more than a year, found that each month of breastfeeding bolstered a 0.3-point increase in intelligence by age 3 and 0.5-point increase by age 7.
The differences held up even when the researchers controlled for parental intelligence, income, employment and education, and the benefit was biggest when babies were breastfed exclusively for the first six months -- a target endorsed by experts but often untenable for working moms.
"We should do whatever we can do to help women carry out their decision to breastfeed," said study author Dr. Mandy Belfort, a neonatologist at Boston Children's Hospital, assistant professor of pediatrics at Harvard Medical School, and lead author of the study published Tuesday in the journal JAMA Pediatrics.
While three out of four new moms start out breastfeeding, less than half continue for six months or more, according to the U.S. Centers for Disease Control and Prevention. Just 15 percent breastfeed exclusively for six months -- the benchmark set by the American Academy of Pediatrics.
"I can understand as well as anyone the challenges of continuing to breastfeed once a mom goes back to work," said Belfort, who is a mother of three. "I think our findings definitely support an investment in helping moms breastfeed their babies."
The study is not the first to link breastfeeding to later intelligence. A 2010 study published in the journal Pediatrics found that children who were breastfed for six months or more outscored their formula-fed classmates in tests of reading, writing and math at age 10. But how breastfeeding confers its brainy benefits remains unclear.
"I don't think anyone knows the answer to that question," said Belfort, speculating that breast milk may contain some unidentified nutrient that benefits the developing brain. "There may also be something about the bonding between mother and infant during those many, many, many hours that may play a role."
The omega-3 fatty acid docosahexaenoic acid, or DHA, has long been suspected to confer some of breast milk's benefits, leading companies like Mead Johnson to supplement their formulas with the fatty acids. But the scientific evidence for doing so is mixed, with some studies suggesting it has positive effects on brain development and others failing to confirm the benefits.
Similarly, studies comparing the later intelligence of preterm babies fed formula or donor breast milk have generated conflicting results. According to a 2007 Cochrane Database Systemic Review, which tallies the latest scientific data, there was no evidence that preterm infants fed donor milk had long-term neurodevelopmental advantages over those fed formula. The review authors suggested more properly designed trials are needed.
Susan Burger of the New York Lactation Consultant Association said she hopes the increasing evidence for the benefits of breastfeeding will translate into more support for new moms.
"I think it's great that there's another one of these studies," Burger said. "But all the studies in the world aren't going to help if women can't get support."