Breast milk, but not infant formula, promotes the growth of unique and more beneficial colonies of bacteria in a newborn’s intestinal tract, according to a new study published in the journal Current Nutrition & Food Science.

Led by Dr William Parker – associate professor at Duke University Medical Center, USA – the research investigated whether formula feeding instead of breastfeeding could influence the type and development of intestinal bacteria known to confer several health benefits to the infant.

The scientists discovered that human milk possesses a unique property that makes it more effective in enhancing the infant’s immune system.

‘This study is the first we know of that examines the effects of infant nutrition on the way that bacteria grow, providing insight to the mechanisms underlying the benefits of breastfeeding over formula feeding for newborns,’ said Dr Parker.

The lab tests demonstrated that, unlike infant formula, breast milk promotes healthy colonisation of the newborn’s intestine. It is this intestinal flora that improves digestion and nutrient absorption but, more importantly, it renders the infant more resistant to infection and diseases.

The team explained that the findings revealed that only breast milk feeds the friendly bacteria in such a way that the bacteria multiply along the infant’s intestinal tract to form biofilms, a concentration of thin, adherent linings that act as a shield against pathogens. The lab results showed that infant formulas do not have the same effect on the bacteria which, instead, travel randomly in the infant’s body and, therefore, do not form the protective biofilms.

Previous research have already established that breast milk is superior to infant formula: breastfeeding protects newborns from infections; makes them less prone to allergies; enhances cognitive and social skills and lowers their risks of developing illnesses such as Type 1 diabetes and multiple sclerosis later in life. And now, studies are explaining how crucial an infant’s early diet is on the development of the intestinal microbial universe which is indispensable for proper human digestion.

Study details

The research team grew cultures of bacteria in samples of breast milk, cow’s milk and three popular brands of milk and soy-based infant formulas. These specimens were then incubated with two strains of E.Coliem bacteria, required for the early growth of healthy intestinal flora. They are helpful relatives of the dangerous E.Coli bacteria known to cause food poisoning.

The bacteria started colonising the three samples almost immediately but they developed differently. In the breast milk, the bacteria adhered together to form biofilms whereas those in the two other specimens proliferated wildly but as individual organisms that did not aggregate to form the protective shield. The team concluded that breast milk assists bacterial association through various mechanisms.

Dr Gabriela Panayotti, from Duke, said: ‘This study adds even more weight to an already large body of evidence that breast milk is the most nutritious way to feed a baby whenever possible.’ She added that breastfeeding is also beneficial for the mother as it reduces cancer risks.


    Zhang et al (2013) Human Whey Promotes Sessile Bacterial Growth, Whereas Alternative Sources of Infant Nutrition Promote Planktonic Growth. Curr Nutr Food Sci. 8(3):168-176(9).