COW MILK FEEDING INDUCES ANTIBODIES TO INSULIN IN CHILDREN - A LINK BETWEEN COW MILK AND INSULIN-DEPENDENT DIABETES-MELLITUS

Exposure to cow milk (CM)-based formulas in early infancy has been ass ociated with an increased risk of insulin-dependent diabetes mellitus (IDDM), but studies on the possible pathogenic mechanism(s) linking CM and IDDM are contradicting. We hypothesized that if CM formulas conta ined bovine insulin (BI), exposure to them could lead to immunization against insulin, which is the only known beta-cell-specific autoantige n in IDDM. We measured immunoglobulin G (IgG) antibodies by enzyme imm unoassay (ELA) to BI and human insulin (HI) in children who received, during the first 9 months of life, either a formula containing whole C M proteins or a formula containing hydrolyzed casein (HC) peptides. BI was detectable by radioimmunoassay (RIA) and immunoblotting in the CM -based formula. At 6 months of age the children who received CM formul a had higher levels of IgG antibodies to BI than children who received either HC formula or children who were exclusively breast-fed (median levels 0.480 versus 0.185, P=0.04; and 0.480 versus 0.160, P=0.04; re spectively). Also, at 9 months of age, children in the CM group differ ed from the HC group (0.403 versus 0.230; P=0.02). Antibodies to BI an d HI showed a positive correlation and cross-reacted in inhibition stu dies, The high incidence of insulin-binding antibodies in young childr en with IDDM may be explained by oral immunization to BI present in CM . Exposure to BI, which differs from HI only by three amino acids, may break the tolerance to insulin.