Food and immunological development.

The infant's host defence is deficient in IgA for mucosal protection and also in IgG2 for protection against encapsulated bacteria. The baby is provided with about one gram a day of milk secretory IgA antibodies against most intestinal microorganisms and also food proteins. These milk antibodies together with a number of other defence factors in the milk protect the baby against gastrointestinal and respiratory infections. Maternal undernutrition does not necessarily diminish the milk IgA concentration or 24 hour output. The infant seems to be low in secretory IgA antibodies for several months as studied in saliva. It is of great importance to protect mucosal membranes especially the intestinal mucosa, so that its nutrient uptake is not disturbed. Infections in infancy especially in the gastrointestinal tract is an important cause of undernutrition. The human milk antibodies against cow's milk and soy protein may decrease the exposure to these food proteins during weaning and possibly decrease the risk of developing allergy. Soy oil can contain soy protein, which may explain some food intolerance reactions.