Sharon Donovan of the University of Illinois examined molecules called HMOs, which are not food for babies, but do feed beneficial bacteria in the gut. Donovan says these bacteria can protect against infection and strengthen the immune system.
Human milk abounds in HMOs, but formula doesn't have them, so other sugars called prebiotics are added. Donovan compared HMOs with the formula version, and found bacteria did better on HMOs.
"We're just looking at one small aspect, but we know that breastfeeding and breast milk does a lot of other things for the infant," Donovan said in a statement.
The study was published in the Journal of Nutrition.