What they are
Glucosamine and chondroitin are key components for building healthy cartilage. They contribute to the creation of substances called proteoglycans, which act as a sponge within cartilage to hold in the water necessary for springy, resilient joints.

Glucosamine, as the name reflects, is a combination of glucose (a sugar) and an amino acid. Chondroitin is a complex chain of linked molecules called mucopolysaccharides. Glucosamine and chondroitin are sold as separate supplements or as a mixture, which may be the most beneficial way to take them.

Where they come from
The body makes small amounts of glucosamine and chondroitin. The glucosamine in a supplement bottle, however, is derived from chitin (from crab, shrimp, and lobster shells). Chondroitin supplements use cartilage from pigs, chicken, fish, or cows as a source material.

Why they're used
Osteoarthritis is the primary reason people use glucosamine and chondroitin as dietary supplements. They can be taken orally or applied as a topical cream to a sore joint (Journal of Rheumatology, 2003, vol. 30, no. 3). In addition to joint health, glucosamine and chondroitin can be used to promote wound healing and to treat the pain, swelling, and joint noises of temporomandibular joint syndrome (TMJ). Currently, researchers are exploring how glucosamine may help reduce the frequency and intensity of migraines and how chondroitin may help benefit the cardiovascular system. As a nasal spray, chondroitin may even help reduce snoring.

How they work
When you take glucosamine as a supplement, most of it ends up in joint tissues. Glucosamine enters an area in the joints called the chondrocytes?cartilage-building factories?where it is used to create new, healthy crops of proteoglycans.

Research supports the use of glucosamine and chondroitin to treat TMJ, migraines, atherosclerosis, kidney stones, and even snoring. Chondroitin has an additional benefit. Its negative electrical charge means that each chondroitin molecule is pushed apart slightly from nearby molecules. This creates small spaces within the cartilage matrix that are then filled with water. The water that fills in the spaces acts as a shock absorber for the compression caused by joint movement. This action makes the pairing of glucosamine and chondroitin particularly beneficial for easing osteoarthritis pain.

Scientific support
There is little doubt that glucosamine and chondroitin help heal joints and prevent and treat osteoarthritis. One group of scientists tracked down every study of glucosamine and chondroitin conducted between 1980 and 2002. After scrutinizing the results, they reported that both compounds, even when taken independently of each other, were exceptionally effective in treating osteoarthritis (Archives of Internal Medicine, 2003, vol. 163, no. 13).

The other effects of glucosamine and chondroitin have not been studied as extensively, but scientifically sound and promising research does exist supporting their role in wound healing, TMJ, migraines, atherosclerosis, kidney stones, and snoring.

Most research has been based on the glucosamine sulfate form, but glucosamine HCl and N-acetyl-glucosamine are available in supplements that also may be effective. Unlike glucosamine, chondroitin generally is available in only one form: chondroitin sulfate.

The standard glucosamine dose is 1,500 mg per day. The standard dose of chondroitin is 1,200 mg per day.

A monthly supply of glucosamine or chondroitin alone costs approximately $20. A combination product ranges from $20 to $50 per month.

Side effects
These supplements are exceedingly safe. No serious side effects have been reported, aside from an occasional case of stomach upset in about 3 percent of users.

Oregon-based freelance writer Victoria Dolby Toews, MPH, is the author of User?s Guide to Sexual Satisfaction (Basic Health Publications, 2003) and User?s Guide to Glucosamine and Chondroitin (Basic Health Publications, 2002).