Q: Is there any evidence that glucosamine and chondroitin can prevent arthritis?
A: This is an excellent question, and it raises an issue of great interest to people who already have arthritis or are worried they may someday develop the disease. Unfortunately, there's no clear-cut answer.
It's important to point out that "arthritis" is a term used to describe more than 100 different diseases. Some of the more common ones include osteoarthritis (also called degenerative joint disease), rheumatoid arthritis and gout. Glucosamine and chondroitin have been studied as a treatment for people who already have osteoarthritis (particularly of the knee). But there's almost no information about their use in other joint diseases.
The interpretation of studies of glucosamine and chondroitin in osteoarthritis are somewhat controversial. But here's how I would summarize the findings:
1. They may be effective as mild pain relievers.
2. Their ability to help arthritic joints heal or improve is uncertain.
3. They seem to have a good safety profile. However, they are not regulated or tested, as prescription drugs must be, so the purity and potency of a particular brand of glucosamine or chondroitin may not be reliable.
The ideal dose and whether they work best when combined (compared with being taken alone) are also unknown.
Finally, it's important to know what type of prevention you have in mind. In "primary prevention," someone who's never had a condition (such as osteoarthritis) takes a medicine or other treatment hoping to prevent that condition from ever developing. As above, there is no scientific evidence that glucosamine or chondroitin is effective for primary prevention of any type of arthritis.
"Secondary prevention" is also controversial. That refers to the ability of these supplements to prevent existing arthritis from getting worse. For example, at least one study found that among a group of patients with osteoarthritis of the knee who took glucosamine, X-rays seemed to improve, and not get worse. But many experts questioned the X-ray methods and whether the apparent improvement may not have been real. A carefully conducted follow-up study did not confirm a protective role for glucosamine or chondroitin.
I don't think there is convincing evidence that glucosamine, chondroitin or the two in combination can prevent osteoarthritis from getting worse. But, stay tuned. Researchers continue to study these popular supplements.
(Robert H. Shmerling, M.D. is a practicing physician in rheumatology at Beth Israel Deaconess Medical Center, Boston, Mass., and an Associate Professor in Medicine at Harvard Medical School.)
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