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Press Release
Arthritis Study Shows Mixed Results for Dietary Supplements
Glucosamine, Chondroitin Sulfate Help Patients with Higher Pain Levels
February 13, 2006
A nationwide clinical trial involving nearly 1,600 patients with osteoarthritis of the knee found little benefit overall for the widely used nutritional supplements glucosamine and chondroitin sulfate, report researchers in the Feb. 23 New England Journal of Medicine. The findings suggest, however, that the supplements may help those with more severe pain.
"The dietary supplements were not effective in treating knee pain due to osteoarthritis in the general study population, but the combination of glucosamine and chondroitin appears to be effective in the subgroup with moderate to severe pain," said lead investigator Daniel Clegg, MD, chief of rheumatology at the University of Utah and the George E. Wahlen Veterans Affairs Medical Center in Salt Lake City.
The trial—funded by the National Institutes of Health and conducted at 16 clinical sites—was the most rigorous trial to date of the dietary supplements, which are taken either alone or in combination by millions of arthritis sufferers in the United States, Europe and elsewhere. Several studies have shown benefits for the supplements, but according to a major analysis published in the Journal of the American Medical Association in 2000, some of those results may have been affected by bias or poor methodology.
The new randomized, double-blind trial involved 1,583 men and women, all age 40 or above, who had been experiencing knee pain for at least six months and showed X-ray evidence of osteoarthritis.
One control group received placebo—a sugar pill with no ostensible therapeutic value—while another control group received 200 mg per day of the pain-reliever celecoxib, sold commercially as Celebrex. The drug is among the newer generation of anti-inflammatories known as COX-2 inhibitors. Concerns arose in 2004 over possible cardiovascular risks of the drugs—which include the now-recalled Vioxx—but celecoxib is generally considered safe at the dose used in this trial.
The remaining three groups of patients received either glucosamine, chondroitin sulfate, or both supplements in combination. The supplements are theorized to work together synergistically.
After six months of treatment, the study team checked how many patients in each group reported a 20-percent or greater reduction in pain, using a questionnaire shown to reliably gauge arthritis pain.
Two-thirds (66.6 percent) of the patients on the supplement combination showed a 20-percent or greater improvement. But this result was almost matched by placebo, which had a response rate of 60.1 percent. The difference was not statistically significant. The individual supplements were slightly less effective than the combination.
Celecoxib, on the other hand, yielded a response rate of 70.1 percent, a statistically significant improvement over placebo.
However, when the researchers looked at the results based on patients' pain levels—1,229 patients had been classified at the study's outset as having mild knee pain, and 354 patients as having moderate to severe pain—the treatment outcome was different.
Most notably, among those with moderate to severe pain, the supplement combo had a response rate of 79.2 percent, compared to 54.3 percent for placebo. The supplement one-two punch numerically outperformed celecoxib, which yielded a response rate of 69.4 percent for this subgroup. For patients with mild to moderate pain, celecoxib performed best, with a response rate of 70.3 percent, versus 62.9 percent for the supplement combo and 61.7 percent for placebo.
According to the authors, the seeming effectiveness of placebo as a treatment is not uncommon in arthritis research, and may have been especially marked in this trial because most of the patients—about 80 percent—had only mild pain to begin with. This same factor, they said, may have made it harder to detect responses to the drug or supplements.
As for side effects from any of the treatments, the authors write that they were "generally mild and evenly distributed among the groups."
Glucosamine and chondroitin sulfate, substances found naturally in the body, help make and maintain cartilage, the rubbery tissue that acts as a shock absorber between bones. Osteoarthritis, the most common form of arthritis, especially among older people, involves the breakdown of cartilage. This leads to inflammation and pain in the joints.
Whether glucosamine and chondroitin-sulfate supplements actually protect or regenerate cartilage has been controversial. Research results have been mixed, and even medical experts who recommend the supplements caution about varying levels of quality control among the more than 200 products on the market that contain one or both of the supplements. Nutrition supplements, unlike medications, are not regulated by the U.S. Food and Drug Administration, although certain manufacturers do state they adhere to pharmaceutical standards. The issue is further complicated because there are different forms of glucosamine: Manufacturers add a stabilizing compound such as hydrochloride or sulfate to the glucosamine base molecule, which contains glucose and the amino acid glutamine.
Study coauthor Domenic Reda, PhD, acting director of VA's Cooperative Studies Program Coordinating Center in Hines, Ill., says further research may help sort out the real benefits of glucosamine and chondroitin sulfate.
"For the moderate to severe group, the combination was quite effective, both clinically and statistically," he noted. "However, only 20 percent of the patients had moderate to severe pain, so we believe the results need to be replicated in a larger trial."
Meanwhile, the bottom line for patients may be to follow the advice of their physician. The authors point out that celecoxib eased pain faster than the supplements, which may be a factor to consider for some patients.
"Given the results of this study, patients would be best-advised to discuss their treatment options with their physicians," said Clegg.
The study was funded by the National Center for Complementary and Alternative Medicine and the National Institute of Arthritis and Musculoskeletal Disease, both components of the National Institutes of Health.
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