Critical Review Chromium in Human Nutrition: A Review

This review summarizes the results of 15 controlled studies supplementing defined Cr(III) com pounds to subjects with impaired glucose tolerance. Three of these (3-4 /*mol Cr/d for >2 mo) produced no beneficial effects: serum glucose, insulin and lipid con centrations remained unchanged. The remaining 12 in terventions improved the efficiency of insulin or the blood lipid profile of subjects (ranging from mal nourished children and healthy middle-aged individuals to insulin-requiring diabetics). In addition, three cases of impaired glucose tolerance after long-term total parenteral alimentation responding to Cr supplementation have been reported. Chromium potentiates the action of insulin in vitro and in vivo; maximal in vitro activity requires a special chemical form, termed Glucose Tolerance Factor and tentatively identified as a Cr-nicotinic acid complex. Its complete structural identification is a major challenge to chromium research. The de velopment and validation of a procedure to diagnose chromium status is the second challenge. Such a test would allow the assessment of incidence and severity of deficiency in the population and the selection of chromium-responsive individuals. The third challenge is the definition of chromium's mode of action on parameters of lipid metabolism that have been reported from some studies but not others. Future research along these lines might establish whether chromium deficiency is a factor in the much discussed "Syndrome X" of insulin resistance. J. Nutr. 123: 626-633, 1993.