Stick-and-ball model of the glucosamine molecule (from the Wikimedia Commons, image by Benjah-bmm27)
Osteoarthritis, the “wear-and-tear” type of arthritis, affects a great many of us as we grow older. Knee pain is a common symptom. The diet supplements glucosamine and chondroitin have been proposed as a more “natural” treatment than pharmaceuticals, and they are components of a number of proprietary “joint health” formulations like Osteo Bi-Flex. The GAIT study (Glucosamine/Chondroitin Arthritis Intervention Trial), compared glucosamine, chondroitin, a combination of the two, and a pharmaceutical (celecoxib) to a placebo in patients with knee pain from osteoarthritis. The only one that worked better than placebo was celecoxib. I wrote about the GAIT trial in 2008. The study was reported in the media as both negative and positive. The positive reports emphasized the subgroup analysis: in one of ten subgroups, patients with moderate to severe pain, the combination of glucosamine and chondroitin outperformed placebo. But in the subgroup of patients with mild to moderate pain, it did not. The authors themselves commented that their study was not powered to draw any conclusions from subgroups and that further studies would be required. (The “power” of a study is a measure of its ability to show an association or relationship between two variables if such a relationship exists.) Now a further study with sufficient power claims to have confirmed the subgroup findings. This may encourage some people to try glucosamine/chondroitin, but I remain skeptical.
Glucosamine is widely used for osteoarthritis pain. It is not as impossible as homeopathy, but its rationale is improbable. As I explained in a previous post,
Wallace Sampson, one of the other authors of this blog, has pointed out that the amount of glucosamine in the typical supplement dose is on the order of 1/1000th to 1/10,000th of the available glucosamine in the body, most of which is produced by the body itself. He says, “Glucosamine is not an essential nutrient like a vitamin or an essential amino acid, for which small amounts make a large difference. How much difference could that small additional amount make? If glucosamine or chondroitin worked, this would be a medical first and worthy of a Nobel. It probably cannot work.”
Nevertheless, glucosamine (alone or with chondroitin) is widely used, and there are some supporting studies. But they are trumped by a number of well-designed studies that show it works no better than placebo, as well as a study showing that patients who had allegedly responded to glucosamine couldn’t tell the difference when their pills were replaced with placebos. The GAIT trial was a large, well-designed, multicenter study published in The New England Journal of Medicine that showed no effect in knee osteoarthritis. A subsequent study of hip osteoarthritis also showed it worked no better than placebo.
A new study shows that glucosamine works no better than placebo for osteoarthritis pain in the low back. It was published in the JAMA: Effect of Glucosamine on Pain-Related Disability in Patients with Chronic Low Back Pain and Degenerative Lumbar Osteoarthritis: A Randomized Controlled Trial, by Wilkens et al. (more…)