NUTRITION: Checking out supplement for joint pain
Glucosamine, often recommended for joint pain, is one of the most popular supplements on the market. And, considering the health concerns recently associated with nonsteroidal anti-inflammatory medications, I thought it would be worth looking into whether glucosamine lives up to the hype.
Glucosamine and chondroitin are often combined to treat osteoarthritis, which occurs when cartilage covering the end of the bone near the joint breaks down. Osteoarthritis affects the knees, backs, hips, hands and feet of more than 21 million people older than 45. And about 90 percent of the population will suffer from osteoarthritis by age 75, according to Dr. Roland W. Moskowitz, professor of medicine at Case Western Reserve University's Arthritis Translational Research Program.
What is it?
Glucosamine and chondroitin sulfate are found naturally in the body. Glucosamine is a form of amino monosaccharide (sugar) believed to play a role in cartilage formation and repair. Chondroitin sulfate is part of a large protein molecule that provides cartilage elasticity. The glucosamine and chondroitin in supplements are extracted from animal tissue: glucosamine from crab, lobster or shrimp shells, and chondroitin sulfate from animals such as sharks.
How it works
Glucosamine is believed to stimulate and repair joint cartilage, ease pain and slow deterioration. Chondroitin fights harmful enzymes that destroy cartilage and helps surviving cartilage retain water and elasticity. Most research, however, is focused on glucosamine.
Although many experts say the specifics of how it works aren't known, Dr. Jean-Yves Reginster, director of the World Health Organization Collaborating Center for Public Health Aspects of Rheumatic Diseases, University of Liege, Belgium, says, "Glucosamine has been shown to reverse several of the negative effects of interleukin-1 (IL-1) on the joints. IL-1 promotes both joint inflammation and joint destruction."
Does it work?
According to Reginster, the original crystalline glucosamine sulfate 1,500-milligram once-a-day formulation, approved as a prescription drug in Europe and available as a supplement in the United States, "has been shown to be effective [in treating osteoarthritis of the knee] in two separate long-term clinical trials of three years duration. Besides symptom control, these two trials showed that the compound was able to delay the joint structural changes. This would allow glucosamine sulfate to be possibly classified as the first disease-modifying agent in osteoarthritis."
In a key review of available glucosamine studies by the Arthritis Center at Boston University School of Medicine reported in the Journal of the American Medical Association, the authors concluded: "Trials of glucosamine and chondroitin preparations for OA symptoms demonstrate moderate to large effects, but quality issues and likely publication bias suggest that these effects are exaggerated. Nevertheless, some degree of efficacy appears probable for these preparations."]
One of the authors, Dr. David Felson, professor of medicine at Boston University School of Medicine, has since modified his opinion: "There's a good chance we've been hoodwinked. Most of the successful trials were funded by industry, and all three of the public, nonindustry studies have shown no impact from using glucosamine."
Yet others take a more pragmatic approach. Moskowitz, for example, says, "There's enough evidence that you can't simply dismiss glucosamine." And according to surgeon C. Thomas Vangsness Jr., professor at the University of Southern California Keck School of Medicine, about 25 percent of glucosamine users are probably experiencing a placebo effect, meaning they feel better, but it's not caused by the glucosamine. "And that's OK, too," he adds.
Even the Arthritis Foundation believes there is emerging evidence that for people with osteoarthritis of the knee, glucosamineprovides a number of benefits, including symptom relief, improved function and a slowdown in cartilage damage.
One of the most important clinical trials of glucosamine for osteoarthritis of the knee is the Glucosamine/Chondroitin Arthritis Intervention Trial being conducted by the National Institutes of Health). Although the results will not be reported until the end of this year, glucosamine advocates are anticipating potential negative findings, claiming that the trial is not testing the original glucosamine sulfate 1,500-milligram once-a-day formulation used in the other trials, but rather a previously untested capsule of 500 milligrams of glucosamine hydrochloride taken three times daily.
Is it safe?
One finding that seems to be undisputed is that glucosamine is generally safe. A recent review in the journal Food and Chemical Toxicology found that "glucosamine is safe and does not affect glucose metabolism."
"Glucosamine seems to be a very safe agent, and I certainly do not discourage people from taking it," says Dr. Anisur Rahman, a senior lecturer in rheumatology at University College London. There are, however, a few populations for whom it's not recommended, including pregnant or breast-feeding women and people with liver disease or shellfish allergies.
What's the right dose?
Advocates can't agree -- some suggest 1,500 milligrams of glucosamine once a day; others say 500 milligrams three times a day. Glucosamine sulfate is suggested over glucosamine hydrochloride for best results.
"The latter has been studied insufficiently in clinical trials, and the few studies conducted show fewer benefits," Reginster says.
And what you see isn't always what you get.
An independent study by ConsumerLab.com found that some manufacturers were putting less glucosamine and chondroitin in their products than stated on the labels. Of the 25 brands tested, one-third failed. View the results at www.consumerlab.com/results/gluco.asp.