Glucosamine is available as a nutritional supplement in health food stores and many drug stores. Glucosamine supplements are manufactured in a laboratory from chitin, a substance found in the shells of shrimp, crab, lobster, and other sea creatures. In additional to nutritional supplements, glucosamine is also used in sports drinks and in cosmetics.
Glucosamine is often combined with chondroitin sulfate, a molecule naturally present in cartilage. Chondroitin gives cartilage elasticity and is believed to prevent the destruction of cartilage by enzymes. Glucosamine is sometimes combined with methylsulfonylmethane, or MSM, in nutritional supplements.
Why Do People Use Glucosamine?
Glucosamine supplements are widely used for osteoarthritis, particularly knee osteoarthritis. In osteoarthritis, cartilage -- the rubbery material that cushions joints -- becomes stiff and loses its elasticity. This makes the joint prone to damage and may lead to pain, swelling, loss of movement, and further deterioration.
Since the body's natural glucosamine is used to make and repair joint cartilage, taking glucosamine as a nutritional supplement is thought to help repair damaged cartilage by augmenting the body's supply of glucosamine.
There is promising evidence that glucosamine may reduce pain symptoms of knee osteoarthritis and possibly slow the progression of osteoarthritis. For example, a study published in the journal Archives of Internal Medicine examined people with osteoarthritis over three years. Researchers assessed pain and structural improvements seen on x-ray. They gave 202 people with mild to moderate osteoarthritis 1,500 mg of glucosamine sulfate a day or a placebo.
At the end of the study, researchers found that glucosamine slowed the progression of knee osteoarthritis compared to the placebo. People in the glucosamine group had a significant reduction in pain and stiffness. On x-ray, there was no average change or narrowing of joint spaces in the knees (a sign of deterioration) of the glucosamine group. In contrast, joint spaces of participants taking the placebo narrowed over the three years.
One of the largest studies on glucosamine for osteoarthritis was a 6-month study sponsored by the National Institutes of Health. Called GAIT, the study compared the effectiveness of glucosamine hydrochloride (HCL), chondroitin sulfate, a combination of glucosamine and chondroitin sulfate, the drug celecoxib (Celebrex), or a placebo in people with knee osteoarthritis.
Glucosamine or chondroitin alone or in combination didn't reduce pain in the overall group, although people in the study with moderate-to-severe knee pain were more likely to respond to glucosamine.
One major drawback of the GAIT Trial was that glucosamine hydrochloride was used rather than the more widely used and researched glucosamine sulfate. A recent analysis of previous studies, including the GAIT Trial, concluded that glucosamine hydrochloride was not effective. The analysis also found that studies on glucosamine sulfate were too different from one another and were not as well-designed as they should be, so they could not properly draw a conclusion. More research is needed.
Still, health care providers often suggest a three month trial of glucosamine and discontinuing it if there is no improvement after three months. A typical dose for osteoarthritis is 1,500 mg of glucosamine sulfate each day.
Other conditions for which glucosamine is used include rheumatoid arthritis, inflammatory bowel disease (Crohn's disease and ulcerative colitis), chronic venous insufficiency, and skin conditions, although further evidence is needed.
Side Effects and Safety of GlucosamineMost studies involving humans have found that short-term use of glucosamine is well-tolerated. Side effects may include drowsiness, headache, insomnia, and mild and temporary digestive complaints such as abdominal pain, poor appetite, nausea, heartburn, constipation, diarrhea, and vomiting. In rare human cases, the combination of glucosamine and chondroitin has been linked with temporarily elevated blood pressure and heart rate and palpitations.
Since glucosamine supplements may be made from shellfish, people with allergies to shellfish should avoid glucosamine unless it has been confirmed that it is from a non-shellfish source. The source of glucosamine is not required to be printed on the label, so it may require a phone call to the manufacturer.
There is some evidence suggesting that glucosamine, in doses used to treat osteoarthritis, may worsen blood sugar, insulin, and/or hemoglobin A1c (a test that measures how well blood sugar has been controlled during the previous three months) levels in people with diabetes or insulin resistance.
Theoretically, glucosamine may increase the risk of bleeding. People with bleeding disorders, those taking anti-clotting or anti-platelet medication, such as warfarin, clopidogrel, and Ticlid, or people taking supplements that may increase the risk of bleeding, such as garlic, ginkgo, vitamin E, or red clover, should not take glucosamine unless under the supervision of a healthcare provider.
The safety of glucosamine in pregnant or nursing women isn't known.