Chromium is an essential mineral known to potentiate insulin action. Recent reviews of chromium supplementation in humans have shown chromium to improve the efficiency of insulin and blood lipid profiles in most test subjects. Chromium is believed to exert this action by binding with nicotinic acid and amino acids (e.g. glutathione: glutamate, cysteine, and glycine) to form an organic complex called glucose tolerance factor (GTF). GTF is thought to initiate the disulfide bridge that allows insulin to bind to its receptor on cell membrane surfaces. The exact structure of GTF is not known, but complexes with good biological activity have been synthesized from chromium, niacin, and glutathione.

While the absorption of chromium is relatively poor, chelating chromium with various amino acids (or their derivatives) appears to increase its bioavailability. Ascorbic acid also promotes the absorption of chromium.

Chromium concentration in foods is variable, but the best food sources are generally fruits, vegetables, and grain products. Seeds, legumes, and dark chocolate can also contain dietarily significant amounts of chromium.

Since dietary chromium is poorly absorbed, adverse effects are not seen with typical dietary and supplemental intakes.