Later studies fail to back earlier research
The Irish Times
Health Supplement, p. 13
22 April 2008
DOES IT WORK?: Chondroitin and osteoarthritis
CHONDROITIN CAME to public attention in combination with glucosamine as a treatment for osteoarthritis. Last week’s column looked at the growing evidence that glucosamine alone may be effective for some people with osteoarthritis.
Safe, effective treatments for osteoarthritis are needed as it is the most common form of arthritis, leading to much pain and interfering with daily activities, especially among the elderly. Treatment has been limited to pain-relievers and anti-inflammatory drugs, although exercise, weight-loss and physiotherapy play an important role in therapy.
Chondroitin is a naturally occurring component of cartilage in most mammals. Osteoarthritis involves the breakdown of cartilage, so consuming chondroitin was anticipated to strengthen cartilage and even repair damaged cartilage. Most commercial chondroitin is made from the cartilage of cows. Chondroitin has become a very popular dietary supplement for osteoarthritis both on its own and in combination with other supplements.
Evidence from studies
During the 1990s, several studies were published on testing chondroitin for osteoarthritis. All reported that patients using chondroitin had either more pain relief or better mobility compared with those getting a placebo (or sugar pill). A specific product containing chondroitin, glucosamine and manganese was found to be particularly helpful.
Sales of chondroitin grew steadily as arthritis sufferers learned about these encouraging results. However, these early studies were relatively small and short, none lasting more than a year. Many involved fewer than 100 patients, with the largest having about 150.
Since 2001, seven high-quality studies have been published, with five finding chondroitin to be no better than placebo. Many of these enrolled hundreds of patients, with two having more than 600. Some of them lasted nearly three years. Overall, the higher-quality studies have found no benefit for patients taking chondroitin.
The situation is somewhat confusing now. When all 20 years of research are summarised, chondroitin appears to be more beneficial than placebo. However, when only higher-quality studies of chondroitin are examined, the benefits disappear. Since the higher the quality of the study, the more reliable its findings, the best evidence suggests that people with osteoarthritis will get little benefit from chondroitin.
Chondroitin usually has few adverse effects, though some people develop heartburn and nausea. There have been concerns that chondroitin may interfere with blood-clotting, but this has not been found in research studies.
However, people taking blood-thinning medication should alert their doctors and pharmacists before taking chondroitin (or any dietary supplement). As chondroitin is made from bovine cartilage, concerns have been expressed that it could transmit animal diseases to humans. No cases of disease transmission from chondroitin products have been reported.
Chondroitin can be relatively expensive. This is partly because it has to be extracted from animals, and partly because it is so difficult to absorb from the digestive tract. This leads to only 10-20 per cent of the dose getting into the body. Because of this, however, it appears that some producers are willing to cut corners with their products to save on their costs.
Studies have also found huge variation in the quality of products. Independent testing has even found a few chondroitin products that contained no chondroitin whatsoever. Use only brands made by reputable manufacturers and never purchase chondroitin from unapproved sources.
In February 2008 the Osteoarthritis Research Society International issued new guidelines for the treatment of osteoarthritis. The best approach combines medications with non-pharmacological approaches. The report found much less evidence favouring the use of chondroitin compared with that for glucosamine. Chondroitin combined with glucosamine appears to be no better than glucosamine alone.
However, the guidelines still concluded that some patients might find chondroitin helpful. In that case, a trial period might be warranted during which the arthritis symptoms should be carefully monitored.
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