Origin: Chondroitin is a component of human connective tissues found in cartilage and bone. In supplements, chondroitin sulfate usually comes from bovine trachea or pork by-products.

Dosage: Capsules, tablets and powder; 800 mg to 1,200 mg daily in two to four divided doses. Often combined with glucosamine. Allow up to one month to notice effect.

Claims: Reduces pain and inflammation, improves joint function and slows progression of osteoarthritis.

What we know: Believed to enhance the shock-absorbing properties of collagen and block enzymes that break down cartilage. Helps cartilage retain water and may reverse cartilage loss when used with glucosamine.

Studies: A large NIH trial of glucosamine and chondroitin showed that the supplements are more effective for decreasing pain when combined than alone. A study of 300 people with knee osteoarthritis who received either chondroitin alone or placebo showed that chondroitin may slow progression of knee OA. A review of more than a dozen studies showed significant improvement in pain and inflammation and improved joint function. Some taking it are able to decrease NSAID dosage.

Some chondroitin tablets may contain high levels of manganese, which could be problematic with long-term use. Because chondroitin is made from bovine products, there is the remote possibility of contamination associated with mad cow disease. Chondroitin taken with blood-thinning medication like NSAIDs may increase the risk of bleeding. If you are allergic to sulfonamides, start with a low dose of chondroitin sulfate and watch for any side effects. Other side effects include diarrhea, constipation and abdominal pain.