Breast-feeding, infant formulas, and the immune system

Objective: Breast-feeding provides many advantages to the offspring, but presently there is an ongoing debate whether or not it prevents allergy any better than certain formulas. This report reviews the mechanisms involved and discusses how breast-feeding may protect against allergy. Data Sources: The review builds on an internet-based literature search in addition to our own data. Results: Human milk is the food best adapted to the needs of the offspring, also because it provides efficient protection against infections and actively stimulates the development of the infant's own immune system. The major host defense system is provided via the secretory IgA antibodies produced in the mammary glands by lymphocytes, which have migrated there from the mother's gut mucosa. Therefore, these antibodies in the milk are primarily directed against the microbes in the mother's gut and her food proteins. As a result, breast-feeding starting directly after delivery will provide an excellent defense against the microbes normally meeting the neonate and needed to induce development of its immune system. The milk also contains numerous components, which seem to enhance the infant's host defense as well as capacity to develop tolerance, helping to avoiding allergic reactivity to foods, etc. Conclusions: Several studies show that breast-feeding prevents allergic diseases, but there are also good disagreeing studies. Supported by animal data, it seems that protection is enhanced in areas with more advantageous fat intake, inter alia lower ratio of n-6/n-3 fatty acids. Breast-feeding seems to protect against future development of allergic diseases, but possibly less so in countries with an untoward maternal fat intake.