At least 7 million Americans take chondroitin, alone or combined with other supplements, for joint pain, current industry figures suggest.
Now, a new study suggests that the supplement may be doing little, if any good.
The study, called a meta-analysis, combines data from 20 prior studies examining the benefits of chondroitin on knee or hip arthritis.
What the analysis found was that chondroitin was only minimally beneficial, if at all, in treating joint pain from arthritis and should not be recommended as treatment.
Many experts say it is little surprise that so many patients are interested in dietary supplements such as chondroitin because current treatments for arthritis are limited and poor.
However, reliable research on chondroitin has thus far been scant -- leading many in the field to question its true effectiveness.
"[This study] accomplished something that is very challenging because the studies of chondroitin are not consistent," said Dr. David Felson, professor of medicine and public health at the Boston University School of Medicine.
"Some of the largest studies have shown no efficacy of chondroitin. Other studies have shown very impressive efficacy. So the question is, what do you believe?"
Arthritis is a degenerative joint disease that affects more than 20 million people in the United States.
It is the most common type of joint disease and a major cause of joint pain because of deterioration of cartilage, which serves as a cushion at the ends of bones that allows for smooth joint movement.
"Originally, the premise behind the use of chondroitin and glucosamine was that they provided the basic elements of healthy cartilage," said Dr. Dennis Boulware, professor of medicine at the University of Alabama at Birmingham.
But Dr. Eric Matteson, chair of the division of rheumatology at the Mayo Clinic in Rochester, Minn., stated, "There is no biologically plausible way that [chondroitin] can work to repair joints damaged by arthritis."
The reason for this, he says, is that even if one were to consume a large amount of the substances that make up cartilage, it seems unlikely that these building blocks would be able to reach the joint where they would be useful, as the cartilage in many joints has no blood supply.
"The substance has to be made and used by cartilage cells to work," Matteson added. "Cells damaged by arthritis cannot do this."
Moreover, Boulware said, "If they really believed that premise, then bald men should eat more healthy hair."
Other research suggests that many patients may not even be getting what they bargained for from their supplement pills. Some chondroitin supplements do not even contain any of the advertised product, as recently discovered by Consumerlabs.com, a leading provider of independent test results and information on health products.
Despite the findings of the new study, some continue to tout the benefits of chondroitin.
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