It has been shown in animal models that dietary factors modify the cytokine profile of islet-infiltrating immune cells, which have an effect on the development of autoimmune diabetes. Weaning to hydrolyzed formula instead of cows' milk formula decreases the incidence of autoimmune diabetes in animal models because of a shift to Th2 cytokine profile in islet-infiltrating T cells. In humans, the evidence from epidemiologic case-control studies and from the first prospective follow-up studies of children at genetic risk of type 1 diabetes is contradictory, and further prospective follow-up studies with longer follow-up times are needed. Furthermore, the available data suggest that risk ratios related to dietary risk factors are relatively low, which implies that the etiologic fraction of an individual dietary factor is small. Despite this, the elimination of an identified risk factor could result in prevention of type 1 diabetes in many children yearly.