Surprising Findings About Breast Milk

A large part of human milk cannot be digested by babies, but it may have a purpose beyond infant nutrition — influencing the composition of the bacteria in the infant's gut.

A particular strain of bacterium, a subspecies of Bifidobacterium longum, possesses a special suite of genes that enable it to thrive on the indigestible component of milk. It coats the lining of an infant's intestine, protecting it from noxious bacteria.

According to the New York Times:

"The indigestible substance that favors the bifido bacterium is a slew of complex sugars derived from lactose, the principal component of milk ... The human genome does not contain the necessary genes to break down the complex sugars, but the bifido subspecies does ... Besides promoting growth of the bifido strain, they also serve as decoys for noxious bacteria that might attack the infant's intestines."

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