Glucosamine and chondroitin are substances naturally found in the body that are also sold as nutritional supplements (nutraceuticals) to help with a variety of conditions.

Most commonly, glucosamine and chondroitin are purported to help strengthen and grow cartilage – the spongy tissue that cushions bones at the joints. People with osteoarthritis (a degenerative joint disease that breaks down cartilage) may take the supplements to relieve chronic joint pain. Some individuals with rheumatoid arthritis, TMJ (temporomandibular joint) disorder and other conditions may also use the supplements for pain relief.

However, none of the uses of the supplements have clear scientific evidence supporting the effectiveness of the products. One large study, conducted by the National Institutes of Health (NIH), indicated that a combination of glucosamine sulfate and chondroitin may help people with moderate to severe osteoarthritis in the knee. However, the supplements were no more effective than a placebo (sugar pill) in relieving mild pain. More studies are necessary to confirm these results.

People with bowel or intestinal tract disorders (e.g., Crohn’s disease, ulcerative colitis, irritable bowel syndrome) may use chondroitin because of its potential anti-inflammatory and immune system stimulating properties. Some studies have indicated that the cartilage building components in chondroitin (made from cow and shark cartilage) may have anti-tumor agents that inhibit cancer growth, according to the National Cancer Institute (NCI).

Both glucosamine and chondroitin occur naturally in the body and primarily act to build and lubricate cartilage and strengthen certain cell walls (such as in the intestinal tract). Unlike vitamins and minerals, which can be found in a variety of fruits or vegetables, there are no natural food sources of glucosamine and chondroitin. Glucosamine supplements are usually made from the shells of crabs, lobsters and shrimp. Chondroitin supplements can be made from the cartilage of cattle or sharks. Both substances can also be made synthetically. Glucosamine and chondroitin supplements may be sold separately or together, and may be combined with other components such as sulfates or manganese.

Supplements of glucosamine and chondroitin are not considered drugs in the United States and are not regulated by the U.S. Food and Drug Administration (FDA). That means there can be a wide variation in the amount of the substances contained in each dose and therefore a significant difference in treatment results. Studies have shown that it may take 12 to 24 weeks for patients taking the supplements to see improvement (if any) in symptoms.

Patients considering supplements should first consult their physician. Experts warn that children and pregnant or breastfeeding women should not use these supplements because there have been no studies about the effect of glucosamine and chondroitin on developing fetuses and children. Other people who may have concerns include individuals with shellfish allergies, asthma or diabetes and people taking certain medications, including anticoagulants and aspirin.