Researchers at the University of California, Davis have discovered that breast milk sugars promote the growth of a subspecies of bacteria important to protecting a baby’s intenstinal lining. The NYTimes reports:
Dr. German sees milk as “an astonishing product of evolution,” one which has been vigorously shaped by natural selection because it is so critical to the survival of both mother and child. “Everything in milk costs the mother — she is literally dissolving her own tissues to make it,” he said. From the infant’s perspective, it is born into a world full of hostile microbes, with an untrained immune system and lacking the caustic stomach acid which in adults kills most bacteria. Any element in milk that protects the infant will be heavily favored by natural selection.