Breast milk has benefitted mammals since mammals evolved. New research shows that the development of milk over eons has not only made it the ultimate super food – it has been designed to hijack bacteria to protect infants. The New York Times reports on new research showing that a large portion of human milk, long known to be indigestible to infants, actually influences the composition of bacteria in the baby’s intestines to protect him or her from harm.

Breast milk is made up of the proteins, minerals and sugars that the baby needs to survive. It is also high in fat, protein, and carbohydrates. And while it has gone in and out of fashion over the years, today people generally recognize breast milk as a healthy start for babies in a world filled with dangerous bacteria. In 2006, around 74 percent of all infants born in the United States were breast fed, while around 44 percent were still being breast fed at six months of age.

About 21 percent of human breast milk contains complex sugars that were long thought to have no dietary significance. This has perplexed experts, who sought to understand why such a large component of breast milk would appear useless to a baby. But a new study out of the University of California, Davis, shows that a certain strain of bacterium has a set of genes that allows it to “thrive” on this particular component of milk. And this bacterium goes on to protect the infant. This is key as infants lack the caustic stomach acids that kill most bacteria in adults and also have weaker immunes systems.

Dr. Bruce German is one of the lead researchers on the study. As he told the New York Times, “We were astonished that milk had so much material that the infant couldn’t digest. Finding that it selectively stimulates the growth of specific bacteria, which are in turn protective of the infant, let us see the genius of the strategy — mothers are recruiting another life-form to baby-sit their baby.”

This particular strain of bacteria is called Bifidobacterium longum, and it coats the lining of the infant’s intestine. Experts feel that it’s presence in human breast milk is the result of 200 million years of evolution and natural selection. It is not present in adult immune systems, but hopes are that this new research will provide insight as to how it could be applied. In fact, scientists hope that it could help premature babies and the elderly.

Dr. German and his colleagues will continue to determine the significance of all components of breast milk. In the meantime, he urges mothers to breast feed. As he told the NY Times, “It’s all there for a purpose, though we’re still figuring out what that purpose is. So for God’s sake, please breast-feed.”

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