Chromium is an essential trace mineral that potentiates insulin action and thus influences carbohydrate, protein, and fat metabolism. The biologically active form of chromium, sometimes called glucose tolerance factor (GTF), occurs naturally in brewers yeast. GTF has been proposed to be a complex of chromium, nicotinic acid (vitamin B-3), and possibly the amino acids glycine, cysteine, and glutamic acid. Although many attempts have been made to isolate or synthesize natural GTF, none have been entirely successful. Adequate chromium nutrition is essential for the formation of GTF and subsequent control of blood glucose levels. Studies have shown that supplemental chromium may be useful for the maintenance of healthy blood sugar. Chromium appears to act by increasing insulin binding, insulin receptor numbers, and rate of insulin receptor phosphorylation. Chromium absorption is typically less than 2% efficient and variable depending on its chemical form. Studies have demonstrated that chromium picolinate has a bioavailability comparable to that of chromium polynicotinate, and higher than that of chromium chloride. Tissues retain anywhere from 2 to 8 times more chromium from chromium picolinate compared to chromium chloride. The typical dietary chromium intake in the U.S. can vary considerably depending on eating habits. Meats and unrefined whole grain cereal products, especially bran, are good sources of chromium. However, most self-selected diets contain less than 50 mcg per day, which is below the minimum of the Estimated Safe and Adequate Daily Dietary Intake established by the National Research Council, Food and Nutrition Board. Chromium requirements may be increased with high intake of refined carbohydrates and simple sugars, strenuous physical exercise or work, infection, or physical trauma.