Chromium Supplementation Does Not Improve Glucose Tolerance, Insulin Sensitivity, or Lipid Profile: A Randomized, Placebo-Controlled, Double-Blind Trial of Supplementation in Subjects With Impaired Glucose Tolerance: Response to Gunton et al.

We read the recent article by Gunton et al. (1) with great interest and feel that it warrants comment. In this study, the authors stated that they “found no beneficial effect of chromium supplementation in the treatment of people with IGT [impaired glucose tolerance].” The results are in conflict with other clinical studies that showed chromium picolinate can enhance or normalize impaired glucose metabolism, as described in a recent review (2). The lack of effect described by the authors may be explained by the apparent low dose of elemental chromium used in the study.

The authors stated that the chromium picolinate “dose (at 800 μg/day) was at the higher end of the ranges used in previous studies” (1). However, chromium picolinate administered at 800 μg per day yields a daily dose of 100 μg per day of elemental chromium (i.e., chromium picolinate contains 12.4% elemental chromium). An elemental chromium dose of 100 μg a day is half of the suggested minimum amount (200 μg) of elemental chromium previously shown to exhibit efficacy in glucose and lipid metabolism (2). A daily dose of 200–1,000 μg of elemental chromium, as chromium picolinate, is the efficacious dosage range used in previous studies.

Bullivants Natural Health Products, the supplier of the study products used by the authors, stated that 400 μg of the chromium picolinate product they produce yields 50 μg of elemental chromium. The study was conducted in Australia, and the 50-μg elemental chromium dose is also the maximum daily dose allowed by the Australian Therapeutic Goods Administration (3).

It was also interesting to note that although the serum chromium levels significantly rose in the active group, the serum chromium levels were not significantly higher in the active group than in the placebo group after 3 months of supplementation (active group 5.2 ± 8.9 nmol/l, placebo group 4.4 ± 4.0 nmol/l). For these reasons, we believe study subjects in the active group may have been administered daily doses of 50 μg elemental chromium, twice daily.

We recommend future studies be conducted in people with impaired glucose tolerance (following criteria defined by the American Diabetes Association) using daily doses of chromium picolinate providing ≥200–1,000 μg of elemental chromium for at least 90 days. We also recommend evaluating efficacy using the 75-g oral glucose tolerance test with calculation of the area under the curve using the trapezoidal method.