Breast Milk and Infant Formula Affect Microflora Differently

Published studies have found preferred health outcomes in breast-fed infants over formula-fed infants. Now, Duke University researchers have discovered key differences in how infant immune systems may respond to each type of early nutrition.

To assess how milk and infant formula might interact with immune systems differently, the researchers inoculated samples of breast milk, infant formula (milk-based and soy-based), cow’s milk, and an abundant antibody in breast milk (SIgA) with two strains of E. coli. Duke University explains the results online:

Within minutes, the bacteria began multiplying in all of the specimens, but there was an immediate difference in the way the bacteria grew. In the breast milk, bacteria stuck together to form biofilms-thin, adherent layers of bacteria that serve as a shield against pathogens and infections. Bacteria in the infant formula and cow’s milk proliferated wildly, but it grew as individual organisms that did not aggregate to form a protective barrier. The bacteria in SIgA had mixed results, suggesting that this antibody by itself isn’t enough to trigger the beneficial biofilm formation.

The SIgA sample offered "mixed results," so there is likely something else in breast milk that causes bacteria to form into a biofilm. Duke University explains that if bacteria congregate into this biofilm organization, it can more effectively support nutrient absorption and immune system development. Lead author and associate professor of surgery at Duke, William Parker, PhD, says this knowledge should promote a new approach to developing infant formulas that more closely mimic breast milk.

More research is warranted on why human breast milk has this effect on the body’s microflora, and whether or not this effect happens against bacteria other than E. coli.

The Duke study on breast milk versus infant formula is now published in the August issue of Current Nutrition & Food Science.