Glucosamine and chondroitin sulfate — two dietary supplements popular with people suffering osteoarthritis — did no better than a placebo in slowing the rate of cartilage loss in the knees, according to a large multicenter study led by University of Utah doctors.

The findings are being published in Arthritis & Rheumatism.

But lead investigator Dr. Allen D. Sawitzke said he would neither encourage nor discourage patients from taking the supplements. "We didn't run into safety issues, so if a patient wants to try them, I don't see a reason to say no. But I can't recommend it; there's no supportive data that says it works," the associate professor of internal medicine at the U. said.

The just-released findings were a follow-up on the randomized Glucosamine/chondroitin Arthritis Intervention Trial (GAIT), which looked at whether people got pain relief with the dietary supplements. In this add-on study, using a subset of patients who wanted to continue the trial an extra 18 months, researchers targeted chondroitin's and glucosamine's other arthritis-related claim: reducing the structural damage of osteoarthritis.

At least 21 million Americans have osteoarthritis, and many of them take one or both of the supplements. The original GAIT study, published in the New England Journal of Medicine in 2006, found no pain relief benefit over placebo, except in a subset of subjects with moderate to severe osteoarthritis knee pain, who got significant pain relief with a combination of the two supplements.

This time, they measured the rate of joint-space width loss and found no significant effect from glucosamine, chondroitin, a combination of the two, celecoxib or a placebo. They did find a trend toward improvement for those with moderate osteoarthritis of the knee who took glucosamine, but with the slow rate of deterioration for all of the participants and without statistically significant improvement for any of them, they couldn't draw conclusions, he said.

The result was complicated by the fact that the damage occurred much more slowly than the researchers had expected, regardless of which of the remedies was taken. And none of them performed statistically better than placebo, but "that's not the same as saying none worked," Sawitzke said. "We had difficulties measuring. The good news is it gets worse slower than we thought. The bad news is we didn't measure enough people to show a difference. Our ability to measure was worse than expected, and the progression was less than expected."

The other centers in the study were The Arthritis Research and Clinical Centers in Wichita, Kan.; University of Arizona in Tucson; Case Western Reserve University in Cleveland; Cedars-Sinai Medical Center in Los Angeles; Indiana University in Indianapolis; University of California, Los Angeles; University of California, San Francisco; and University of Pittsburgh. The national Center for Complementary and Alternative Medicine and the National Institute of Arthritis, Musculoskeletal and Skin Diseases also funded the study.

---

E-mail: lois@desnews.com