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Chromium, Glucose Tolerance, and Insulin Sensitivity
With Comments from Russell H. Greenfield, MD
Dr. Greenfield, Medical Director, Carolinas Integrative Health Carolinas HealthCare System Charlotte, NC, Clinical Assistant Professor, School of Medicine, University of North Carolina, Chapel Hill, NC, is Executive Editor of Alternative Medicine Alert.
Source: Gunton JE, et al. Chromium supplementation does not improve glucose tolerance, insulin sensitivity, or lipid profile. Diabetes Care 2005;3:712-713.
Goal: To determine the effect of supplementation with chromium picolinate on glucose tolerance, insulin resistance, and lipid profile in people with impaired glucose tolerance.
Design: Randomized, double-blind, placebo-controlled trial.
Subjects: Forty subjects (24 females) with proven impaired glucose tolerance recruited from tertiary referral centers in Sydney, Australia.
Methods: Patients were randomized 1:1 to receive either chromium picolinate 400 mg twice daily or placebo over three months. Fasting levels of insulin, chromium, cholesterol, and triglycerides were determined prior to intervention.
Results: At trial’s end the only differences noted were a small increase in serum chromium levels in the active group and a small rise in cholesterol levels in the placebo group.
Conclusions: Chromium supplementation offers no significant benefit to people with impaired glucose tolerance.
Study strengths: Although the sample size was small, the study was sufficiently powered to identify clinically relevant differences between treatment arms.
Study weaknesses: Compliance assessed by tablet count; 800 mg/d is a higher dose than used in some studies, but it is nonetheless a lower dose than what is commonly used in clinical practice (1,000 mg daily).
Of note: An estimated 10 million Americans use chromium supplements, making them the second most popular nutritional supplement; dietary requirements for chromium are controversial, and the present RDA is 0.05-0.20 mg; while many studies of chromium for the treatment of diabetes have been published, results have been inconsistent; subjects were asked not to use chromium supplementation outside the study parameters.
We knew that: The association between chromium deficiency and development of diabetes was first noted in patients receiving long-term parenteral nutrition (diabetes resolved following chromium supplementation, and chromium is now routinely added to TPN solutions); the most appropriate biomarker of adequate chromium status has yet to be identified; chromium is found in many foods including wheat germ, brewer’s yeast, many meats, and a number of vegetables; chromium has been touted as a weight-loss/body-building supplement with little supportive research; one published study suggested that chromium picolinate can cause DNA damage (likely due to the picolinate moiety), but this has not been shown to be true in humans.
Clinical import: With a seemingly ever-increasing incidence of Type 2 diabetes, patients are exploring a wide variety of supplements, especially chromium, to help control the malady and limit complications. This small, but adequately powered, study showed no significant benefit attributable to a moderate dose of chromium picolinate in people with impaired glucose tolerance. Results of studies on chromium for the treatment of diabetes and dyslipidemia have been inconsistent, the dosages used have often not approximated the dosage employed clinically (true even for the present study), and good data are scarce for weight loss and other advertised indications. Unfortunately, a reliable normal range for chromium levels has not yet been established, and it is possible that supplementation may benefit those patients with Type 2 diabetes who are also chromium-deficient. For those using chromium, the picolinate form is perhaps the most popular, but many practitioners steer their patients to GTF (glucose tolerance factor) chromium in part because of the concerns raised about picolinic acid in the single laboratory study cited above. That stated, the data supporting supplementation with magnesium in the setting of insulin resistance/diabetes appear more convincing.
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