We have long known that vaginal birth and breastfeeding are key factors in the development of a healthy immune system in infants. Passing through the vagina exposes the baby to an array of bacteria that help stimulate its unchallenged immune system. Breast-fed babies receive anti-bodies, proteins and other molecules that protect it from infection and teach the immune system to defend the infant.
Recent research at UC Davis has shown that a strain of the bifido bacteria — acquired from the mother — thrives on complex sugars (largely lactose) that were previously thought to be indigestible. The bacterium coats the lining of the immature digestive tract and protects it from noxious bacteria.
This combination of interactions affects the composition of bacteria in the infant gut as it matures. Another example of how evolution has “invented” the perfect nutrition for infants, this research contributes to the notion that evolution has selected for many genes that serve normal birth and breastfeeding by protecting the newborn. Intervening with the normal progression of birth and breastfeeding — while occasionally necessary — interrupts these beneficial adaptations and contributes to allergies and autoimmune disorders.