Experts Still Looking for Glucosamine Attributes

Eager to relieve joint pain and repair the cushioning between bones, millions of arthritis sufferers reach for glucosamine, an over-the-counter dietary supplement.

Despite its popularity, studies examining the effectiveness of this natural therapy have yielded mixed results.

"There is still a lot of uncertainty about glucosamine," says Dr. Steven C. Vlad, a fellow in clinical epidemiology and rheumatology at Boston University School of Medicine.

Glucosamine is a type of sugar that the body produces and distributes in cartilage and other connective tissue.

Chondroitin sulfate, often taken in combination with glucosamine, is a complex carbohydrate that helps cartilage retain water, according to the National Center for Complementary and Alternative Medicine.

These substances are derived from animal tissues, according to the Arthritis Foundation. Glucosamine is extracted from crab, lobster, or shrimp shells, and chondroitin sulfate comes from bovine or shark cartilage.

Study Results on Benefits Vary

Dr. Vlad's own study tried to determine why the results of glucosamine trials differed so widely. Of the 15 studies he reviewed, there was one clear finding: A particular glucosamine preparation, called glucosamine hydrochloride, does not work.

Results among clinical trials involving another common preparation, glucosamine sulfate, showed wider variation than would be expected by chance.

Based on the evidence, Dr. Vlad concludes that supplement industry support could be a source of bias in some of these studies.

Although critics have questioned Dr. Vlad's finding, he stands by the results.

"Numerous analyses have showed that industry funding is correlated with stronger findings and selective publication of positive results," he notes.

More recently, researchers at the University of Utah School of Medicine reported results from a follow-up to an earlier glucosamine study of arthritis patients. Participants in this portion of the study took glucosamine; a combination of glucosamine and chondroitin; the anti-inflammatory drug celecoxib (Celebrex®); or a placebo.

X-rays were taken of patients' knees before the trial began and one and two years later to determine whether glucosamine alone, or in combination with chondroitin, would slow the loss of cartilage.

Lead author, Dr. Allen D. Sawitzke, an associate professor of internal medicine, says he and his colleagues were hoping to show some slowing of the cartilage loss by studying enough patients and gathering accurate measurements. The results, though, were inconclusive.

"So, it's an example of a null study, that is, a study where there is no difference detected, which isn't the same as saying there is no difference," says Dr. Sawitzke.

Some Experts Say Try Glucosamine

Dr. Jason Theodosakis, an assistant professor at the University of Arizona College of Medicine and author of the book, The Arthritis Cure, says the study was flawed in many ways, including the small sample size, short duration, and imprecise X-ray methodology.

Like many physicians, though, Dr. Theodosakis continues to recommend glucosamine and chondroitin. "This study does nothing to discourage that," he says.

Trying glucosamine for 60 days makes sense, especially for patients who cannot tolerate ibuprofen or other nonsteroidal anti-inflammatory drugs, says Dr. Stephen Dahmer, at the VA San Diego Medical Center.

Dr. Sawitzke says he sees some merit in the supplement for pain relief, but there is a lot less evidence to support glucosamine as a way to slow cartilage damage.

Dr. Vlad, however, tells patients he is doubtful it works very well, if at all.

"But I also tell them that it is safe and will not hurt them,” he says. “If they want to try it, they are more than free to do so at any time, with the understanding that no insurance company will pay for it."

Always consult your physician for more information.