Glucosamine and chondroitin: Weighing the claims and the research on arthritis

Glucosamine and chondroitin are taken by more people with osteoarthritis than any other "joint" supplement. But a slew of recent research casts doubt on how well they work. Here's what you need to know.

Both are components of human cartilage, the smooth covering on knee bones and other joints that acts as a shock absorber. In osteoarthritis, cartilage softens, cracks and wears out, allowing knee joints to rub together.

• Glucosamine is thought to be involved in cartilage growth; supplements are derived from the shells of crabs and lobsters.
• Chondroitin gives cartilage its elasticity; supplements are usually derived from animal cartilage.

The claim. Proponents say that glucosamine and chondroitin relieve pain by maintaining cartilage so joint bones don't grind against each other.

The research. There's plenty of conflicting data out there. Belgian researchers recently found that glucosamine had no effect on pain or joint deterioration in people with osteoarthritis in their hips. And a large American study of 1,583 people with osteoarthritis found that this duo didn't ease joint pain any better than placebo pills.

But when researchers looked at the 20 percent of study participants with moderate to severe arthritis pain, they found a benefit: 79 percent of those taking the supplements (who took 500 milligrams of glucosamine plus 400 milligrams of chondroitin three times a day) had at least a 20 percent reduction in pain, compared to 54 percent taking placebos.

What about joint protection? Other studies suggest that these supplements may help maintain joint space — the distance between bones. More joint space means less grinding, less damage and less pain.

In a Belgian study of over 300 women with osteoarthritis, those who took glucosamine for three years showed no narrowing of the space between knee bones, while those taking a placebo saw the gap grow smaller.

The glucosamine group also reported a 14 percent improvement in pain and stiffness from the beginning to the end of the study, while the placebo group was a little worse by the end.

Are they safe? Yes. Long-term studies have found only mild side effects such as intestinal gas and softer bowel movements.

What should I take? The Arthritis Society suggests this pair may be worth a try, but cautions that the data offer no real guarantees.

Take a supplement containing 500 milligrams of glucosamine and 400 milligrams of chondroitin sulfate three times a day. Try it for three months to see if you're getting any noticeable benefit. If not, stop taking the pills.