The study, published in the Annals of Internal Medicine, looked at data from 20 clinical trials encompassing 3,846 patients.
"People had the idea that this could be the magic bullet for osteoarthritis, but it cannot be," said Dr. Peter Juni, a medical epidemiologist at the University of Bern in Switzerland and one of the authors of the study.
The study suggests that there is no point in starting patients on chondroitin, said Dr. David Felson, an osteoarthritis researcher at Boston University who wrote an editorial accompanying the study.
But because there are no serious side effects from the supplement, "If patients say they benefit from chondroitin, I see no harm in encouraging them to continue taking it," he wrote.
Chondroitin sulfate is a compound found in cartilage that is believed to help make joints more elastic. In the U.S., it is usually sold with glucosamine, another compound in cartilage that some believe plays a role in repairing joints.
Americans spent $810 million in 2005 on glucosamine-chondroitin supplements, according to the Nutrition Business Journal.
Juni's team looked at the effect of chondroitin without glucosamine.
Of the 20 trials, the researchers focused on three of the largest and most complete studies, which included 1,553 patients.
They found virtually no difference in pain reduction between the chondroitin and placebo groups. The researchers also looked at X-rays of the patients' joints and found little difference between the two groups.
Juni said the three studies included more patients with advanced osteoarthritis than low-grade osteoarthritis.
Because several smaller studies had shown an improvement for low-grade sufferers, Juni acknowledged that some patients could benefit from chondroitin.
Andrew Shao, a nutrition scientist with the Council for Responsible Nutrition, a Washington-based trade group for supplement makers, said the study was too narrow because it focused on three trials and excluded glucosamine, which may have dampened the effectiveness of chondroitin.
"The conclusion of this particular meta-analysis is not the final word for chondroitin," Shao said.
From the April 23, 2007, Prepared Foods e-Flash