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April 16, 2007 -- Chondroitin, a dietary supplement, works no better than a sugar pill, analysis of clinical data suggests.
In the U.S., chondroitin is almost always combined with glucosamine, another supplement. Annual U.S. sales of the chondroitin/glucosamine combination were $810 million in 2005, according to figures cited by the Council for Responsible Nutrition (CRN), a supplement industry trade group.
And sales "continue to grow at a phenomenal pace," Andrew Shao, PhD, the CRN's vice president for scientific and regulatory affairs, tells WebMD. Shao says only omega-3 supplements sell faster than chondroitin-based supplements.
"Sales continue to grow. This is presumably because consumers are finding a benefit," Shao says.
That benefit appears to be an illusion, suggests Peter Juni, MD, head of clinical epidemiology and biostatistics at the University of Bern in Switzerland.
David T. Felson, MD, MPH, professor of medicine and epidemiology at Boston University, uses stronger language.
"What WebMD readers should take home about the possible efficacy of chondroitin is that it doesn't work," Felson tells WebMD. "The confusion is there was some early evidence suggesting it does work. The better evidence suggests it does not."
Juni's study, and Felson's accompanying editorial, appear in the April 17 issue of Annals of Internal Medicine.
Chondroitin usually comes from animal cartilage. People with osteoarthritis lose cartilage in their joints. Researchers disagree over whether chondroitin taken by mouth ever finds its way to the joint. They also disagree over whether it offers any benefit to people with arthritis.
Juni and colleagues analyzed every clinical study of chondroitin as a treatment for arthritis. The studies focused on chondroitin alone and not in combination with glucosamine.
Early clinical trials showed a fabulous benefit for chondroitin -- in one case finding the supplement was more effective than knee replacement surgery. A close look showed many kinds of problems with these early trials. Three more recent trials avoided these problems.
"Early, methodologically insufficient trials showed overoptimistic benefits for chondroitin," Juni tells WebMD. "The longer people evaluated the drug, the better they evaluated it, the worse the drug looked. In the last few years, large trials showed effects that were nearly or entirely null. It is likely these trials show a reliable estimate of the benefit of this drug, which is zero."
"There is pretty strong evidence it doesn't work any better when combined with glucosamine," Felson says. "There is a huge National Institutes of Health trial and two others showing no effect for chondroitin. And all of the publicly funded studies of glucosamine suggest it doesn't work, either."
Shao disagrees. He says that Juni and Felson are basing their conclusions on just three trials -- and ignoring data from 19 other studies.
"When you can leave out what you want and put in what you want, you get the conclusion that you want," Shao says. "As far as [the Juni study] goes, it is just three of 22 trials. ... Does that mean that they can make a judgment on whether chondroitin works in general for everybody? No."
Neither Juni nor Felson tell their patients to stop taking chondroitin. They do not recommend the supplement. But since it does no harm, they do not argue with patients who say it helps.
"If a patient says he is taking it, I would not bother to tell him to stop," Juni says. "I would say, 'I am not sure the drug is having an effect, but it seems safe, so use it as long as it seems to help.'"
"It is benign stuff, and who am I to know it doesn't help you?" Felson says. "There may be a few patients out there it does help. If you think you are one of these it is fine to keep taking it."
"That is a testimonial to the confidence Dr. Felson and the community of rheumatologists have about the safety of these products," Shao says. "There is a high level of confidence in the scientific community about the safety. Admittedly, we have to disagree on the benefits side."