Glucosamine sulfate, glucosamine hydrochloride, N-acetyl glucosamine

Origin: Major component of joint cartilage. Supplements are derived from the shells of shellfish (such as shrimp, lobster and crab) or from vegetable sources.

Dosage: Capsules, tablets, liquid or powder (to be mixed into a drink); 1,500 mg per day for all forms. Often combined with chondroitin. May take one month to notice effect.

Claims: Slows deterioration of cartilage, relieves osteoarthritis (OA) pain and improves joint mobility.

What we know: Glucosamine produced in the body provides natural building blocks for growth, repair and maintenance of cartilage. Like chondroitin, glucosamine may lubricate joints, help cartilage retain water and prevent its breakdown. Similar to NSAIDs for effectiveness of easing osteoarthritis symptoms but may take twice as long as conventional drugs to work.

Studies: Trial results are mixed, but overall, glucosamine appears to reduce pain and improve function in OA. A 2005 review of 20 glucosamine studies found an improvement in joint pain, stiffness and function with one brand of glucosamine (Rottapharm, marketed as Dona, Viartril and Xicil) but not others.

The largest study to date, the 2006 Glucosamine/chondroitin Arthritis Intervention Trial (GAIT) looked at 1,600 people with knee OA. The first phase found that a small subset of patients with moderate-to-severe arthritis experienced significant pain relief from combined glucosamine and chondroitin. The 2008 phase found that glucosamine and chondroitin, together or alone, did not slow joint damage. And in the two-year-long 2010 phase, glucosamine and chondroitin were found as effective for knee OA as celecoxib (Celebrex).

In a small 2012 study, an improvement in symptoms was seen with combined glucosamine and NSAIDs, and a smaller but still significant improvement with glucosamine alone.

Research also suggests glucosamine may slow joint damage. A 2008 retrospective study of nearly 300 patients found those using glucosamine underwent half as many joint replacement surgeries as those on placebo.

Dosage: Capsules, tablets, liquid or powder (to be mixed into a drink); 1,500 mg once daily or in three divided doses to prevent stomach upset. Often combined with chondroitin. May take up to one month to notice effect.

 Glucosamine may cause mild stomach upset, nausea, heartburn, diarrhea and constipation, as well as increased blood glucose, cholesterol, triglyceride and blood pressure. Don’t use glucosamine if you are allergic to shellfish.

New research suggests that people with glaucoma or intraocular hypertension could have worsening eye pressure if they take a glucosamine supplement.