Chromium is a trace mineral essential nutrient that has been promoted for the prevention and treatment of diabetes based on the fact that chromium deficiency is associated with glucose intolerance. Ten million Americans spend $150 million a year for chromium supplements, making it the best selling mineral supplement after calcium. However the mechanism by which chromium relates to glucose is unknown. Chromium concentrations cannot be measured with accuracy in the body and the amount of normal dietary intake of chromium is uncertain since such a small amount of chromium is absorbed from food that the actual uptake from food is very difficult to measure.
One uncontrolled study showed improvement on a test that is a marker of the stages leading up to diabetes (called the glucose tolerance test) in three out of six diabetics given 1000 micrograms of chromium, with no effect on non-diabetics. Another study compared placebo to trivalent chromium at 200 microgram per day for six weeks followed by a cross over (placebo patients then took chromium). There was no effect on the glucose tolerance test. Another study randomized 76 patients with atherosclerotic disease to 250 micrograms of chromium chloride or placebo for 7-16 months. In the patients with diabetes, there were no differences between the chromium treated patients and the placebo group.
One study randomly assigned 180 Chinese subjects with Type-2 diabetes to two doses of chromium picolinate or placebo for four months. Glucose control was improved with the higher dose of 1000 micrograms per day of chromium as well as on measures of blood glucose and insulin levels. This is the only controlled study of chromium, however, that showed benefit, and more controlled studies need to be done to see if these early results can be replicated. Also, the fact that this was a Chinese sample means that they can’t necessarily be applied to American or European populations, since there may be differences in nutritional status (i.e. chromium supplementation may be replacing a chromium deficiency in the Chinese). For instance, prior studies showing beneficial effects of another trace metal selenium in Chinese could not be replicated in the US.
In summary, there really isn’t good evidence at this point that chromium is helpful for diabetes.