So what is glucosamine, anyway. Vlad, a fellow in clinical epidemiology and rheumatology at Boston University School of Medicine. Vlad's own study tried to determine why the results of glucosamine trials differed so widely. These substances are derived from animal tissues, according to the Arthritis Foundation. "There is still a lot of uncertainty about glucosamine," said Dr.

Chondroitin sulfate, often taken in combination with glucosamine, is a complex carbohydrate that helps cartilage retain water, according to the U.S. Glucosamine is extracted from crab, lobster or shrimp shells, and chondroitin sulfate comes from animal cartilage, such as tracheas or shark cartilage. Results among trials involving another com preparation, glucosamine sulfate, sho wide variation -- more than would be expected by chance.

Of the 15 studies he revie there was one clear finding. Despite its popularity, studies examining the effectiveness of this natural therapy have yielded mixed results. It's a type of sugar that the body produces and distributes in cartilage and other connective tissue. A particular glucosamine preparation, called glucosamine hydrochloride, doesn't work.

National Center for Complementary and Alternative Medicine.