Chromium is not an essential trace element for mammals: effects of a “low-chromium” diet
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Chromium was proposed to be an essential trace element over 50 years ago and has been accepted as an essential element for over 30 years. However, the studies on which chromium’s status are based are methodologically flawed. Whether chromium is an essential element has been examined for the first time in carefully controlled metal-free conditions using a series of purified diets containing various chromium contents. Male Zucker lean rats were housed in specially designed metal-free cages for 6 months and fed the AIN-93G diet with no added chromium in the mineral mix component of the diet, the standard AIN-93G diet, the standard AIN-93G diet supplemented with 200 μg Cr/kg, or the standard AIN-93G diet supplemented with 1,000 μg Cr/kg. The chromium content of the diet had no effect on body mass or food intake. Similarly, the chromium content of the diet had no effect on glucose levels in glucose tolerance or insulin tolerance tests. However, a distinct trend toward lower insulin levels under the curve after a glucose challenge was observed with increasing chromium content in the diet; rats on the supplemented AIN-93G diets had significantly lower areas (P < 0.05) than rats on the low-chromium diet. The studies reveal that a diet with as little chromium as reasonably possible had no effect on body composition, glucose metabolism, or insulin sensitivity compared with a chromium-“sufficient” diet. Together with the results of other recent studies, these results clearly indicate that chromium can no longer be considered an essential element.
KeywordsChromium Rats Glucose tolerance tests Insulin sensitivity Essential trace element
This project was supported by National Research Initiative grant 2009-35200-05200 from the USDA Cooperative State, Research, Educational, and Extension Service to J.B.V. and J.F.R. The authors wish to thank Dyets for working with us to obtain diets with a minimal chromium background concentration and Robert Argent, Jessica Autry, Paul Lara, Kirsten Ansorge, Leigh Ann Pledger, Lauren Bryant, James Shivers, Philip Dishuck, and Kyndal Sonnier for assistance with this work.
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