Immunologic consequences of feeding infants with cow milk and soy products.

Various products and regimens proposed for feeding infants when the mother's milk is not available have been evaluated intensively for capacity to achieve optimal nutrition. The immunologic consequences of feeding the foreign proteins contained in the various products have received much less attention and no systematic investigations have been done for comparable immunologic evaluation. Sera obtained at intervals from normal infants fed cow milk and soybean products from birth in different regimens were analyzed for antibodies to five major milk proteins and a soy protein isolate. Antibody levels increased slowly during the first 4 months, reaching a peak about 6 months of age. In infants fed cow milk products or a soy product from birth to 112 days of age and then given various cow milk products the following antibody responses were observed: The level of serum antibodies attained was highest with pasteurized cow milk and lower with heat-treated cow milk or a milk base formula of lower protein content. Feeding a soy product from birth for 112 days did not prevent a brisk antibody response to cow milk introduced subsequently, comparable to or greater than the antibody response seen when cow milk products were fed from birth. Clinically no immunologic disorders were detected in association with antibody responses to the various products and regimens. The implications of the findings for infant feeding and immunologic disorders are discussed.