Chromium for Type 2 Diabetes?

Summarized by Robert W. Griffith, MD
August 28, 2006

Summary

A study showing that chromium picolinate, taken as a supplement, helps control type 2 diabetes stands in opposition to two previous studies that suggest it's ineffective.

Introduction

Chromium is a metal that's found in some foods, such as meats, animal fats, fish, brown sugar, coffee, tea, some spices, whole-wheat and rye breads, and brewer's yeast. There has been controversy about its use by people with diabetes. There's a lack of rigorous studies to support any evidence of benefit. But a new study from Louisiana State University, published in the journal Diabetes Care, suggests that chromium picolinate may indeed confer significant benefits on body weight and insulin sensitivity.

What was done

Thirty seven subjects were included in the study; they all had type 2 diabetes which was not adequately controlled; fasting blood glucose levels had to be between 125 and 175 mg/dL. After baseline evaluation, they were given long-acting glipizide (Gucotrol-XL®, a sulphonylurea) together with a placebo capsules for 3 months, to ensure clinical stability. Then they were allocated randomly to receive either glipizide plus chromium picolinate (100 micrograms chromium daily) or to continue on glipizide plus placebo, for a further 6 months. There were 17 subjects in the chromium group and 12 in the placebo group.

Measurements made at the start and end of the 6-month test period included urine chromium levels, insulin sensitivity, body weight, body fat (using dual energy X-ray absorptiometry), abdominal fat (by computerized tomography), blood glucose, glucose tolerance, HbA1c, and lipid levels.

What was found

The average age of the subjects was 60, and their average body mass index (BMI) was 30 kg/m² (indicating overweight verging on obesity). Their average HbA1c at baseline was 9.7%. Seventeen of the 25 participants were men.

Chromium was nearly undetectable in the urine collected at baseline, but levels increased significantly in those given chromium picolinate. The following changes were detected in the measures made at the start and the end of the 6-month treatment period:

Changes over 6 months	Chromium	Placebo
Increase in body weight	+ 0.9 kg (2 lb)	+ 2.2 kg (4.8 lb)
Increase in body fat	+ 0.12%	+ 1.17%
Total abdominal fat	12.2 cm/2	32.5 cm/2
Insulin sensitivity	28.8	15.9
Change in HbA1c	- 1.16%	- 0.4%
Fasting glucose decrease mg/dL	- 31.0 mg/dL	- 11.3 mg/dL
Free fatty acids	- 0.2 mmol/L	- 0.12 mmol/L

All the above changes were statistically significant, indicating that the addition of chromium picolinate improved glucose control, insulin sensitivity, and abdominal fat accumulation, compared with the placebo.

There were no serious or untoward adverse effects of chromium picolinate medication reported.

What do these results mean?

The findings in this study have to be set against two negative studies published in 2005¹. In a 6-month, double-blind trial of chromium picolinate (500 and 1,000 microgram daily) in 46 obese poorly controlled type 2 diabetics, researchers found no effect on weight, blood pressure, HbA1c, or lipid profile compared with placebo. The other study reported no benefit on glucose tolerance, insulin resistance, or lipids in 40 patients with impaired glucose tolerance given 800 micrograms daily for 3 months, despite evidence of increased serum chromium levels. Clearly these results need to be reconciled with those from the study summarized here. Hopefully, a 4-year study of 1,000 micrograms daily of chromium picolinate in lean to obese individuals with type 2 diabetes, sponsored by the National Institutes of Health (NIH), will provide some answers.

Chromium supplements are believed to be the second most frequently taken nutritional supplement, used by an estimated 10 million people in the USA. There is probably no question of safety, therefore. Chromium is poorly absorbed and rapidly excreted from the body, so that toxicity is only to be expected in people with impaired kidney function.

What's a poorly controlled type 2 diabetic to do with this information? As the lead investigator in this most recent study says, a daily supplement of 400-800 micrograms of chromium "seems to be the dose that is safe and well tolerated" in studies showing a positive effect; it's extremely unlikely to do harm. People already taking chromium should probably continue to do so (it's relatively inexpensive). On the other hand, there isn't sufficient evidence, yet, to recommend that patients not already taking chromium should begin now. Why not wait for the result of the NIH-sponsored study in a year or so?

The best and safest source of chromium is food. Whole grains, ready-to-eat bran cereals, seafood, green beans, broccoli, prunes, nuts, peanut butter, and potatoes are rich in chromium. And more enjoyable than supplements.

Source

• Chromium picolinate supplementation attenuates body weight gain and increases insulin sensitivity in subjects with type 2 diabetes. J. Martin, ZQ. Wang , XH. Zhang ,  et al. , Diabetes Care, 2006, vol. 29, pp. 1826--1832

Footnotes
1. Kleefstra N, Houweling ST, Jansman FG, et al. Chromium treatment has no effect in patients with poorly controlled, insulin-treated type 2 diabetes in an obese western population: A randomized, double-blind, placebo-controlled trial. Diabetes Care 29: 521-525, 2006. Gunton JE, Cheung NW, Hitchman R, et al. 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. Diabetes Care 28:712-713, 2005.

Related Links
Chromium - The Controversy Continues
UC Berkeley Wellness Guide to Supplements: Chromium
NIH Supplements Fact Sheet: Chromium

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