Chromium absorption, safety, and toxicity

Trivalent chromium (Cr) as Cr chloride is very poorly absorbed (0.5-2%), and many trials with animals and humans have not demonstrated toxicity. Absorption of Cr is affected by various factors in the gastrointestinal tract, including ascorbic acid and fiber components. Different Cr salts as well as different forms of Cr have diverse solubilities. Furthermore, the amount of Cr presented affects absorption, with a lower percentage from higher doses. Many people in the United States have Cr intakes in the 20-30 mu g/day range. Certain medications that inhibit prostaglandin synthesis, such as aspirin and indomethacin, markedly enhance uptake of Cr-51. Buffering compounds, such as magnesium or calcium carbonates or hydroxides reduce Cr-51 absorption. Occupational exposure to hexavalent Cr is a health concern. Hexavalent Cr is potentially a carcinogen when inhaled, but usual acidity of the stomach reduces it to the trivalent form. Despite the general assumption of safety of trivalent Cr, the widespread use of Cr supplements, particularly by diabetic patients, warrants more extensive monitoring of safety for long-term use. J. Trace Elem. Exp. Med. 12:163-169, 1999. (C) 1999 Wiley-Liss, Inc.