It has been speculated that chromium supplementation might improve insulin sensitivity in patients with type 2 diabetes. This theory stems from the fact that this essential trace mineral has been shown to aid glucose metabolism, and its deficiency is known to lead to glucose intolerance and insulin resistance.

A 6-month double-blind study that was recently published in Diabetes Care (2006;29:521-525) sought to determine the effects of chromium supplementation on glycemic control in a group of 53 patients (aged <75 years) with type 2 diabetes who had a hemoglobin (Hb) A1c level >8% and required >50 units per day of insulin. All had a body mass index >25 kg/m2 (mean [± SD], 34 ± 5.2). Patients were randomized to 1 of 3 groups: 250 µg chromium picolinate twice daily (n = 17), 500 µg chromium picolinate twice daily (n = 17), or placebo (n = 19). The primary end point was a change in HbA1c.

The patients were asked not to make any changes to their diet or their insulin dosages. No alterations were made in cholesterol-reducing, antihypertensive, or oral hypoglycemic regimens during the 6-month study period. The supplements used in the study were made with chromium picolinate containing 12% chro­mium. The participants took 1 supplement tablet with breakfast and another one with dinner.

At study onset, the duration of diabetes, diabetes treatments, other medication use, and insulin requirements were recorded. Patients were weighed, their height was measured, and their blood pressure was taken. Levels of serum creatinine, hemoglobin, alanine aminotransferase, HbA1c, serum total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, and plasma chromium were also determined. All of these measurements (with the exception of height) were taken again at 1, 3, and 6 months.

A total of 46 patients completed the study. No significant differences were reported over the 6-month study period for the 3 groups. Supple­men­tation with chromium picolinate 250 or 500 µg had no effect on weight, blood pressure, HbA1c, or lipid profile compared with placebo, according to lead investigator Nanne Kleefstra, MD, of Isala Clinics, Weezenlanden, Zwolle, the Netherlands, and colleagues.

“Based on our results, there is no convincing evidence that chromium therapy in an obese Western diabetic population will improve glycemic regulation or the parameters of the insulin resistance syndrome,” they wrote.

They added, however, that these results may not apply to every diabetic population, since this analysis only included patients with poorly controlled diabetes who required large quantities of insulin.

The most frequently available form of chromium supplements are chromium salts (ie, chromium polynicotinate, chromium picolinate, chromium chloride), which enhance absorption compared with chromium isolate.

Although no recommended daily allowance has been established for chromium, the estimated safe and adequate daily dose is 120 µg/day, according to the Institute of Medicine.