Unlike infant formula, breast milk promotes more beneficial growth of gut flora, the colonies of friendly bacteria that help absorb nutrients and develop the immune system. This may explain why it is better than formula at protecting newborns from infection and illness, according to a new US study published as an epub ahead of print in the journal Current Nutrition & Food Science this week.
Senior author William Parker, associate professor of surgery at Duke University Medical Center, Durham, North Carolina, in the US, told the press:
“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 breast feeding over formula feeding for newborns.”
“Only breast milk appears to promote a healthy colonization of beneficial biofilms, and these insights suggest there may be potential approaches for developing substitutes that more closely mimic those benefits in cases where breast milk cannot be provided,” he explained.
Researchers have already established that breast-milk feeding reduces diarrhea, flu and respiratory infections in babies, and lowers their risk of developing allergies, type 1 diabetes, multiple sclerosis and other diseases later in life. And, more and more studies are suggesting some of this could be due to the effect of early diet on the development of the microbial universe in the gut without which human digestion doesn’t function.
For their study, Parker and colleagues grew cultures of bacteria in cow’s milk, infant formula, and human breast milk.
For the cow’s milk they used whole milk sold in grocery stores, for the infant formula they used three popular brands of milk and soy-based products. The breast milk was donated by volunteers.
They separated the breast milk into various components, including proteins, fats and carbohydrates. And they also ran some tests comparing breast milk with a purified form of secretory immunoglobulin A (SIgA), infant formulas and cow’s milk. SIgA is an antibody that is abundant in human breast milk, and helps develop the infant’s immune system.
They incubated the SIgA, cow’s milk, human breast milk and infant formulas with two strains of E. coli, two types of bacteria that are essential for the early development of gut flora colonies. They are friendly relatives of the E. coli bacteria that cause food poisoning.
It only took minutes for the bacteria to start growing, in all the samples. However, the colonies developed differently in the different samples.
In the human breast milk sample, the bacteria clung together and formed biofilms: an essential layer of flora that acts as a barrier against pathogens and infection.
This did not happen in the cow’s milk and infant formula samples: the bacteria in those cultures grew prolifically, but as individual organisms, more like plankton that you find in the ocean than a biofilm of associated cells.
In the SIgA sample, the results were in between the two, suggesting SIgA on its own is not enough to cause aggregation that is enough to make a biofilm.
Also, bacterial aggregation occurred over a broader range of bacterial concentrations in the breast milk sample than in the SIgA: “affecting the aggregation of bacteria at concentrations 1000-fold less than could be mediated by SIgA,” note the authors.
They conclude that their study shows human breast milk uses “multiple mechanisms to facilitate bacterial association”. In contrast, infant formula and cow’s milk encourage more plankton-like colonies of bacteria.
The authors suggest the study gives some important clues about how human milk might protect against infections and illnesses.
Parker said the findings could also help develop infant formula that is better at mimicking nature.
“This could have a long-lasting effect on the health of infants who, for many reasons, may not get mother’s milk.”
He said more research was needed to find out why human breast milk encourages the clumping of E. coli bacteria to produce a biofilm, and whether it does this to other strains of bacteria.
Parker said additional studies should explore why human whey has the clumping effect on the bacteria, and whether it has a similar effect on strains of bacteria other than E. coli.
The Fannie E. Rippel Foundation and a pre-college research fellowship from the Howard Hughes Medical Institute helped finance the study.
Written by Catharine Paddock PhD