These substances are derived from animal tissues, according to the Arthritis Foundation. Vlad, a fellow in clinical epidemiology and rheumatology at Boston University School of Medicine. It's a type of sugar that the body produces and distributes in cartilage and other connective tissue. 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. Despite its popularity, studies examining the effectiveness of this natural therapy have yielded mixed results. A particular glucosamine preparation, called glucosamine hydrochloride, doesn't work.

National Center for Complementary and Alternative Medicine. Of the 15 studies he revie there was one clear finding. Chondroitin sulfate, often taken in combination with glucosamine, is a complex carbohydrate that helps cartilage retain water, according to the U.S. Based on the evidence, Spike concluded that supplement industry support could be a source of bias in some. So what is glucosamine, anyway.

"There is still a lot of uncertainty about glucosamine," said Dr.

Vlad's own study tried to determine why the results of glucosamine trials differed so widely.