LETTERS

Is further research needed on glucosamine?

The review “Do glucosamine and chondroitin worsen blood sugar control in diabetes?” (J Fam Pract 2006; 55:1091–1093) is timely and important, given that glucosamine is a popular supplement with potential to adversely affect glucose homeostasis. The authors state that short-term glucosamine administration does not affect glycemic control and speculate that long-term effects are unlikely to be different. However, they advocate for additional investigations (including long-term studies) in patients with poorly controlled diabetes or glucose intolerance.

A recent paper of ours sheds some light on the health concerns of glucosamine supplements at standard doses (500 mg orally, 3 times daily).¹ This paper and others² have shown that peak plasma concentrations of glucosamine achieved after a 500 mg oral dose are 1000- to 10,000-fold less than the mM concentrations of glucosamine used in cell-based, animal, or human studies demonstrating effects of glucosamine to cause insulin resistance.^2,3 Moreover, giving glucosamine to humans at standard oral does of 500 mg 3 times daily does not cause any changes in steady-state levels of plasma glucosamine. It’s unlikely that exogenously administered glucosamine will be transported into cells where it may impact on glucose homeostasis. Indeed, endogenous glucosamine production (~12 g/day) is considerably higher³ than standard oral doses of glucosamine supplements.

In our study, using state-of-the-art methods to measure insulin sensitivity and endothelial function, we did not observe any evidence that glucosamine supplements at standard doses for 6 weeks cause or worsen insulin resistance or endothelial dysfunction in healthy or obese subjects. We do not believe that more studies evaluating the safety or efficacy of oral glucosamine for longer durations in patients with poorly controlled diabetes are warranted.

Ranganath Muniyappa, MD, PhD
and Michael J. Quon, MD, PhD
Diabetes Unit, Division of Intramural
Research, National Center for Complementary
and Alternative Medicine,
National Institutes of Health, Bethesda, Md;
muniyapr@mail.nih.gov

REFERENCES

1. Muniyappa R, Karne RJ, Hall G, et al. Oral glucosamine for 6 weeks at standard doses does not cause or worsen insulin resistance or endothelial dysfunction in lean or obese subjects. Diabetes 2006;55:3142–3150.
2. Biggee BA, Blinn CM, McAlindon TE, Nuite M, Silbert JE. Low levels of human serum glucosamine after ingestion of glucosamine sulphate relative to capability for peripheral effectiveness. Ann Rheum Dis 2006;65:222–226.
3. Anderson JW, Nicolosi RJ, Borzelleca JF. Glucosamine effects in humans: a review of effects on glucose metabolism, side effects, safety considerations and efficacy. Food Chem Toxicol 2005;43:187–201.

The Journal of Family Practice ©2007 Quadrant HealthCom Inc.