Effectiveness of Glucosamine and Chondroitin for Osteoarthritis

TO THE EDITOR: This article repeated a common misconception about the Glucosamine/Chondroitin Arthritis Intervention Trial (GAIT), interpreting it as showing that the combination of glucosamine and chondroitin is effective for treating moderate to severe osteoarthritis.1 The study found that glucosamine and chondroitin, separately or in combination, were not more effective than placebo. Only one of 10 subgroups showed statistically significant results, and these were for moderate to severe arthritis. With 10 subgroups, it is likely that chance alone would produce false-positive results in one of these groups. The authors of the study warned that it was not powered to differentiate among subgroups, and that no clinical recommendations should be made based on that finding.1

The AFP article recommends a combination of glucosamine and chondroitin as the third step in a stepped-care approach for the treatment of osteoarthritis. This is not justified by the evidence. In addition, the rationale is suspect because glucosamine and chondroitin are produced by the body. The amount added by taking supplements is only a minuscule fraction of what is already present. These are not essential nutrients like vitamins, of which taking a small amount is likely to make a large difference.

Dr. Hall is a contributing editor to both Skeptic magazine and the Skeptical Inquirer. She is a weekly contributor to the Science-Based Medicine blog and is one of its editors. She has also contributed to Quackwatch and to a number of other respected journals and publications. She is the author of Women Aren’t Supposed to Fly: The Memoirs of a Female Flight Surgeon and co-author of the textbook, Consumer Health: A Guide to Intelligent Decisions.