Selenium and copper in type 2 diabetes mellitus - more doubt than certainty

Type 2 diabetes mellitus (T2DM) is one of the most common chronic illnesses nearly all over the world and the prevalence of this disorder is still growing. Particularly in industrialized countries, it has become the most serious global medical and public problem, next to cancer and cardiovascular diseases. Despite intensive developments in the research on T2DM pathogenesis, the impact of nutritional factors, and particularly the effect of trace elements, on the development of this disease has not been identified completely, although relationships between some elements, e.g. Zn, Fe, Cr, and T2DM have been described in detail. Critical review of the literature indicates that the majority of inconsistencies appear in studies on Cu and Se: on the one hand, these minerals have strong antioxidant properties and even insulin-mimetic action; on the other hand, an increased risk of T2DM positively correlates with a high dietary intake of Se and Cu or supplementation with these elements. High content of these minerals in diets observed in selected countries and/or increasing popularity of dietary supplementation with Se or Cu, especially among chronically ill patients including ones with T2DM, can cause distortions in the molecular pathways of glucose metabolism. The influence of these minerals on inducing diabetic complications is even more vague and depends on several factors, e.g. the body status of these and other trace elements, the type of complications and the duration of T2DM. The relationship between T2DM and the status of Se and Cu is complex and bidirectional, thus a well-balanced diet providing these trace elements in proper amounts, according to the demand of an organism, may be one of the strategies in reducing the risk of T2DM and its complications.