A major constituent of human cartilage that is believed to contribute to cartilage’s elasticity and resilience. Chondroitin is also available as a dietary supplement for treating osteoarthritis (OA).

The supplement form of chondroitin is generally taken from cow cartilage. It is often used in tandem with the supplement glucosamine. Glucosamine is another naturally occurring substance in cartilage, and it is thought to inhibit inflammation and stimulate cell growth.
Over the past decade, people with OA have turned increasingly to chondroitin and glucosamine to relieve joint pain. Studies, however, have not consistently backed up the claims of these supplements. The largest study on the supplements, called GAIT (Glucosamine/Chondroitin Arthritis Intervention Trial), recruited over 1,500 people who had experienced knee pain for over six months and whose x-rays showed evidence of OA. The only group of people within the study that seemed to benefit from the combination of glucosamine and chondroitin were those with moderate to severe OA of the knee. Of these, 79.2% experienced pain relief with the supplements, compared with 54.3% taking a placebo (inactive pill). The group was small, however, and the data were not strong enough to prove the effectiveness of the supplements.

Furthermore, choosing a chondroitin supplement can be tricky, since there is no guarantee that the products contain the ingredients in the amounts stated on the label. Experts recommend looking for the United States Pharmacopoeia (USP) symbol on the label, as an indicator of quality, or looking up the supplement at, which evaluates supplements for quality and purity. There is no “recommended dose” of chondroitin, but most suggest taking 400 milligrams, two or three times a day. Users may need to take it for 6 to 8 weeks before seeing any improvement.

Chondroitin’s side effects appear to be mild and include indigestion, nausea, headache, rash, and hives. Chondroitin is similar in structure to the blood-thinning drug heparin, and taking it in addition to heparin, aspirin, or other blood-thinners can raise the risk of bleeding complications. Children, pregnant women, and women who could become pregnant should not take chondroitin — there are not enough data on the supplement’s effects in these cases. Be sure to tell your doctor if you’re taking chondroitin or other supplements, especially if you’re experiencing side effects. And it is important to remember that chondroitin is meant only to supplement a drug or exercise program, not to replace it.

Robert S. Dinsmoor is a medical writer and editor based in Massachusetts.

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