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As naturally occurring substances in the body, glucosamine and chondroitin are known to build and lubricate cartilage and strengthen certain cell walls (such as in the intestinal tract). While there are many purported benefits to taking these substances in supplement form, there is no clear scientific evidence of their effectiveness. Nevertheless, glucosamine and chondroitin supplements are popular as complementary and alternative medicine (CAM) therapy for a variety of conditions and disorders.

The most common use of glucosamine and chondroitin supplements is in relief of chronic pain associated with osteoarthritis (degenerative joint disease), particularly osteoarthritis of the knee. In a normal joint, glucosamine and chondroitin (two substances that occur naturally in the body and help build cartilage) work together to keep the joint functioning smoothly. When osteoarthritis or other disorders affect the joint, cartilage and other joint tissue may break down or become inflamed, typically resulting in pain and stiffness of the affected area(s). Weight-bearing joints, such as the knees, hips and spine, are most often affected. Other causes of joint pain for which glucosamine and chondroitin supplements have been used include rheumatoid arthritis, a chronic autoimmune disorder that destroys joint tissue, and temporomandibular joint (TMJ) disorder, a cause of jaw pain.

The Natural Standard Research Collaboration (NSRC) (an international group that rates the effectiveness of complementary and alternative therapies) notes that glucosamine and chondroitin have been used without scientific backing in attempts to treat or prevent many conditions that can be serious and require medical attention.

Patients should consult their physician for treatment of any condition before taking supplements. Some of these conditions include AIDS, angina (a type of chest pain), athletic injuries, back pain, cancer, depression, diabetes, fibromyalgia, joint pain, knee pain, heart disease, inflammatory bowel disease, kidney stones, migraine headaches, immunosuppression, pain, psoriasis, wound healing and osteoporosis.

The effect glucosamine and chondroitin has on diseases, if any, is still being investigated, but there are some theories on how they may work:

• Inflammatory bowel diseases (e.g., Crohn’s disease, ulcerative colitis). These conditions involve inflammation of the lining of the digestive tract. Glutamine – the amino acid that binds with the sugar glucose to form glucosamine – plays a key role in maintaining healthy cells in the intestinal walls (mucosal cell integrity).  The mucous membranes inside the gut help prevent organisms (bacteria and other germs) from permeating those cell walls and causing inflammation and other complications. Some studies indicate glucosamine may strengthen intestinal cell walls and reduce inflammation.
  
  
• Cancer. Chondroitin has been taken by some patients as a cancer-fighting aid. According to the National Cancer Institute’s review of several studies, chondroitin may interfere with the growth of blood vessels in tumors by encouraging cartilage growth. Tumors cannot grow or survive without blood vessels. Or some of the components in the cartilage may be toxic to tumor cells. However, more research is needed to determine the anti-tumor mechanisms involved and long-term effectiveness of the supplement. In addition, researchers in Boston recently found chondroitin to be ineffective in reducing women’s risk of ovarian cancer.
  
  
• Interstitial cystitis. Chronic bladder inflammation. Chondroitin’s potential anti-inflammatory properties may decrease inflammation.

The NSRC offers the following categories for conditions that may be treated with the two supplements:

Although the NSRC has noted strong scientific evidence for the treatment of osteoarthritis with supplements, the National Institutes of Health has found that glucosamine and chondroitin were not any more effective than a placebo when used for mild knee pain. The NIH did find that the supplements appeared effective in reducing pain for people with moderate to severe knee pain.