DURHAM, N.C. — Its widely known that human milk makes for healthier infants than formula, but not all of the reasons are clear.
Duke University Medical Center researchers may have just found one: Human milk promotes the growth of biofilms of beneficial bacteria that line the intestinal tract of healthy babies, helping digestion and the development of the immune system and acting as a barrier to bad germs.
The study, which appears in this months edition of the journal Current Nutrition & Food Science, is the first the researchers know of that looks at the effects of infant nutrition on the way these bacteria grow, said William Parker, an associate professor of surgery at Duke and senior author of the study.
Among other implications, it could be a step toward engineering healthier formula for babies who cant get human milk, said Parker.
The research team grew key types of bacteria in four types of samples: cows milk, breast milk, several brands of milk- and soy-based infant formula, and an antibody found in human milk known to help establish an infants immune system.
The bacteria grew in all four. But in the cows milk and formula, each of the one-celled organisms floated around freely by itself. In breast milk, they grew in the filmlike colonies that are normally found in the intestinal tract. In the antibody, the results were mixed.
Earlier studies have shown that breast milk has a host of beneficial effects including reducing rates of flu and respiratory infections in infants and protecting against later onset of several diseases.
The results of the new study underline the complexity of how human milk produces benefits for infants, said Dr. Miriam Labbok, director of the Carolina Global Breastfeeding Institute at UNC-Chapel Hills Gillings School of Global Public Health.
This is a really neat finding, Labbok said. Its an interesting thing and one of those wow moments you get when you are studying how human milk and other things work together.
She said the study helps increase understanding of the effects of human milk, and that it could lead to other discoveries.
Labbok was skeptical, though, of the notion that it could lead to better infant formula. The complexity of the effects of human milk on infants means that just pulling out one benefit and trying to mimic it wouldnt work.
Parker said his group doesnt have money to research how the findings might improve infant formula. The Duke researchers are planning to work with N.C. State University scientists to at least explore one question raised by the study: Whether cows milk could do a better job creating the beneficial biofilms.
Its possible, he said, that the scientists might have gotten better results by using something other than store-bought, processed milk, and instead had used, say, milk straight from the animal.