Dose Response Benefits and Safety of Elevated Intakes of Trivalent Chromium by Humans. Richard A. Anderson, USDA/ARS, Beltsville Human Nutrition Research Center, Nutrient Requirements and Functions Laboratory, Beltsville, MD 20705
The beneficial effects of supplemental chromium are associated with the degree of glucose intolerance. Consumption of diets in the lowest quartile of normal intake (less than 20 Tg/d) by control subjects with good glucose tolerance results in no change in glucose and insulin variables. However, consumption of these same diets by people with marginally impaired glucose tolerance leads to negative effects on glucose and insulin metabolism that are reversed by 200 Tg/d of supplemental Cr as Cr chloride. People with diabetes appear to have still higher requirements for Cr. Improvements in blood glucose, hemoglobin A1c, insulin and cholesterol are greater in people with type II diabetes receiving 1000 Tg/d of Cr as Cr picolinate than in those receiving 200 Tg/d. The Estimated Safe and Adequate Daily Dietary Intake (ESADDI) for Cr as established by the U.S. National Research Council is 50 to 200 Tg. The reference dose for Cr established by the U.S. EPA is 70,000 ug/d. However, the reference dose is based primarily on insoluble forms of chromium such as chromic oxide and may not apply to soluble forms of Cr. Recent dose response studies using rats given water soluble, Cr chloride, and lipid soluble, Cr picolinate, failed to demonstrate any signs of toxicity in rats consuming up to 100 mg of Cr per kg of diet. There was a linear increase in tissue Cr concentrations with significantly greater incorporation for Cr as Cr picolinate. On a per kg basis, these levels are several thousand times the upper limit of the ESADDI for humans. Absorption of Cr by humans and animals is usually less than two percent and in vitro studies or studies involving injected Cr may have little relevance to the toxic levels of Cr taken by normal means. There is a large safety factor relating the beneficial effects of Cr to the reference dose and no studies have documented any toxic effects of trivalent Cr in nutrition studies involving supplemental Cr up to 1000 Tg/d.