Chromium has long been of interest for its possible connection to various health conditions. Among the most active areas of chromium research are its use in supplement form to treat diabetes, lower blood lipid levels, promote weight loss, and improve body composition.
- Type 2 diabetes and glucose intolerance
In type 2 diabetes, the pancreas is usually producing enough insulin but, for unknown reasons, the body cannot use the insulin effectively. The disease typically occurs, in part, because the cells comprising muscle and other tissues become resistant to insulin’s action, especially among the obese. Insulin permits the entry of glucose into most cells, where this sugar is used for energy, stored in the liver and muscles (as glycogen), and converted to fat when present in excess. Insulin resistance leads to higher than normal levels of glucose in the blood (hyperglycemia).
Chromium deficiency impairs the body’s ability to use glucose to meet its energy needs and raises insulin requirements. It has therefore been suggested that chromium supplements might help to control type 2 diabetes or the glucose and insulin responses in persons at high risk of developing the disease. A review of randomized controlled clinical trials evaluated this hypothesis . This meta-analysis assessed the effects of chromium supplements on three markers of diabetes in the blood: glucose, insulin, and glycated hemoglobin (which provides a measure of long-term glucose levels; also known as hemoglobin A1C). It summarized data from 15 trials on 618 participants, of which 425 were in good health or had impaired glucose tolerance and 193 had type 2 diabetes. Chromium supplementation had no effect on glucose or insulin concentrations in the non-diabetic subjects nor did it reduce these levels in subjects with diabetes, except in one study. However, that study, conducted in China (in which 155 diabetics were given either 200 or 1,000 mcg/day of chromium or a placebo) might simply show the benefits of supplementation in a chromium-deficient population.
Overall, the value of chromium supplements for diabetics is inconclusive and controversial . Randomized controlled clinical trials in well-defined, at-risk populations where dietary intakes are known are necessary to determine the effects of chromium on markers of diabetes .
The effects of chromium supplementation on blood lipid levels in humans are also inconclusive [1,8,37]. In some studies, 150 to 1,000 mcg/day has decreased total and low-density-lipoprotein (LDL or “bad”) cholesterol and triglyceride levels and increased concentrations of apolipoprotein A (a component of high-density-lipoprotein cholesterol known as HDL or “good” cholesterol) in subjects with atherosclerosis or elevated cholesterol or among those taking a beta-blocker drug [38-40]. These findings are consistent with the results of earlier studies [41-44].
However, chromium supplements have shown no favorable effects on blood lipids in other studies [45-50]. The mixed research findings may be due to difficulties in determining the chromium status of subjects at the start of the trials and the researchers’ failure to control for dietary factors that influence blood lipid levels [9-10].
Body weight and composition
Chromium supplements are sometimes claimed to reduce body fat and increase lean (muscle) mass. Yet a recent review of 24 studies that examined the effects of 200 to 1,000 mcg/day of chromium (in the form of chromium picolinate) on body mass or composition found no significant benefits . Another recent review of randomized, controlled clinical trials did find supplements of chromium picolinate to help with weight loss when compared to placebos, but the differences were small and of debatable clinical relevance . In several studies, chromium’s effects on body weight and composition may be called into question because the researchers failed to adequately control for the participants’ food intakes. Furthermore, most studies included only a small number of subjects and were of short duration .