Diet and the development of clinical diabetes in man.

Current concepts in the aetiology of diabetes mellitus in man (Fig. I) emphasize its heterogeneity (Cudworth & Festenstein, 1978) and the interaction of heredity and environment in the development of all types of clinical diabetes (Keen & Jarrett, 1976). There is little evidence to suggest that nutritional factors might play a significant role in the aetiology of idiopathic insulin-dependent (Type I) diabetes. In this type of diabetes the inherited factors are HLA-linked and probably related to the immune response system and the environmental factors are largely unidentified but are thought to include viral infections. On the other hand, idiopathic insulin-independent (Type 11) diabetes shows no association with the HLA system and there is nothing to suggest that viral infections have anything to do with its development. The inherited element is even stronger than in insulin-dependent diabetes (Pyke & Nelson, 1976) but it is not clear what defect is inherited. That heterogeneity exists within this type of diabetes also is demonstrated by the recent observation that the intense facial flush experienced by some diabetics taking chlorpropamide (CPAF) is a dominantly inherited trait associated with insulin-independent diabetes (Leslie & Pyke, I 978). The demonstration that this reaction can be blocked with naloxone suggests that these patients may have inherited an unusual sensitivity to enkephalins (Leslie et al. 1979). It has long been recognized that obesity and idiopathic insulinindependent diabetes often co-exist. Although at one time it was considered that obesity was an integral part of the diabetic state, arising from, rather than causing diabetes, most people would now agree that obesity probably acts as a diabetogenic environmental factor in those genetically predisposed to develop diabetes (Baird, 1973a,b). In this paper I shall consider whether there is any evidence that, obesity apart, specific nutritional factors are involved in the aetiology of Type I1 diabetes.