Insulin in human milk and the prevention of type 1 diabetes.

Although controversial, exclusive breast milk feeding was shown to exert a protective effect in preventing type 1 diabetes. In contrast, an early introduction of cow's milk-based formula in young infants may enhance the risk of disease, especially in genetically susceptible children, presumably by an increase of intestinal permeability to macromolecules such as bovine serum albumin and beta-casein, which may arouse autoimmunity. We have shown that human milk contains insulin in substantial concentrations, while insulin is barely detectable (if at all) in infant formulas. Orally administered insulin was demonstrated to promote gut maturation and to reduce intestinal permeability to macromolecules. Furthermore, oral insulin may induce tolerance to insulin and protect against the development of type 1 diabetes. We herewith raise a hypothesis that human milk is protective against the development of type 1 diabetes by virtue of the effects of its substantial content of insulin.