Those who sell nutritional supplements often claim their pills possess enormous health-promoting powers. Sure, we all need nutrients, especially if we don't eat a well-balanced diet, but taking megadoses of minerals, herbs, supplements and other compounds may provide only marginal benefits.
Scientists, however, are finding that glucosamine and chondroitin, touted for their ability to relieve the pain of arthritis, might actually work. Even "Quackwatch," a not-for-profit corporation created to "to combat health-related frauds, myths, fads and fallacies," concurs. In an article posted on the group's Web site (http://www.quackwatch.org) the founder, Dr. Stephen Barrett, concedes that glucosamine "may stimulate production of cartilage-building proteins," while chondroitin "may inhibit production of cartilage-destroying enzymes."
The evidence that these two compounds are beneficial seems to be mounting.
In the meantime, millions of Americans take glucosamine and chondroitin for arthritic knees, which, according to some studies, seem to repair themselves slightly after several weeks.
An article titled "Glucosamine and Chondroitin Effective for Knee Osteoarthritis," published in the December 2003 issue of the Journal of Family Practice, called glucosamine and chondroitin "viable first-line treatment options to reduce the symptoms of knee osteoarthritis."
Dr. Terry Seaton and his co-authors examined all the studies they could find on glucosamine and chondroitin and consistently saw evidence that these substances might prove beneficial. They found, for example, that patients who took 1,500 mg of glucosamine a day for three years suffered less shrinkage of the space in the knee joint between the shin bone and the thigh bone. That suggests the cartilage that cushions the bones was deteriorating more slowly in those people, so they suffered less of the pain that results when the two bones rub against each other.
"The vast majority of my patients who try glucosamine and chondroitin say they work," said Dr. Seaton, an associate professor of pharmacy at the St. Louis School of Pharmacy. "You need to take them for several weeks before getting the full benefit, but if they're going to have any benefit for you, you'll know in the first month or so."
Glucosamine and chondroitin are often included in the same pill, but they appear to act differently. Glucosamine, extracted from the shells of shellfish, seems to inhibit inflammation and may bolster or even repair knee cartilage. It probably does this, scientists say, by stimulating the production of a protein that gives cartilage its elasticity.
Chondroitin, derived from cow cartilage, seems to help human cartilage maintain its fluid levels. It also appears to prevent certain body enzymes from degrading cartilage in the knee.
The NIH study, known as GAIT (Glucosamine/Chondroitin Arthritis Intervention Trial), focuses on knee arthritis. Participants are divided into five groups and receive either glucosamine alone, chondroitin alone, glucosamine and chondroitin together, celecoxib (Celebrex) only, or a placebo.
"I believe the NIH study will probably be the landmark study in regard to glucosamine and chondroitin and the knee," said Dr. Hayes Wilson, a rheumatologist and medical adviser for the Arthritis Foundation.
Knee arthritis is particularly troubling to women after menopause, but an article published in the spring journal Menopause found that glucosamine reduces the progression of the disease in postmenopausal women.
The popularity of glucosamine and chondroitin soared after the 1997 publication of The Arthritis Cure, by Jason Theodosakis, a sports medicine specialist in Tucson, Ariz. Despite the book's title, Theodosakis does not claim the two supplements will eliminate the symptoms of arthritis, but he does make a compelling case that they provide relief from pain, and may even preserve the precious cartilage that cushions the joints.
Americans spend more than $700-million a year on glucosamine and chondroitin, according to the Nutrition Business Journal. That can be pricey for a nutritional supplement - close to $1 a day for someone taking 1,500 mg per day. Glucosamine is a substance produced naturally by the body, therefore the supplements cause few side effects. There was some concern that glucosamine might raise sugar levels in diabetics, but a study published in 2003 found that was not the case.
Even though the GAIT study won't be finished for at least another year, few risks seem involved in taking the supplements now, doctors say.