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Glucosamine is an important building block needed by the body to manufacture specialized molecules called glycosaminoglycans, found in cartilage.
GS supplementation has significantly reduced symptoms of osteoarthritis in uncontrolled and single-blind trials. Many double-blind trials have also reported efficacy. One published trial has reported no effect of GS on osteoarthritis symptoms. While most research trials use 500 mg GS taken three times per day, results of a three-year, double-blind trial indicate that 1,500 mg taken once per day produces significant reduction of symptoms and halts degenerative changes seen by x-ray examination. GS does not cure people with osteoarthritis, and they may need to take the supplement for the rest of their lives in order to maintain benefits. Fortunately, GS appears to be virtually free of side effects, even after three or more years of supplementation. Benefits from GS generally become evident after three to eight weeks of treatment.
Where is it found?
Who is likely to be deficient?
Which form is best?
GS is stabilized with one of two mineral salts: sodium chloride (NaCl) or potassium chloride (KCl). Although they both appear to effectively stabilize GS, the use of KCl as a stabilizer seems preferable since the average Western diet already provides far too much salt (NaCl) and not enough potassium. However, most of the research has been done with the NaCl-stabilized form.
Concerns have been raised about the quality of GS products on the market. In one study, the amount of glucosamine contained in 14 commercially available glucosamine products varied from 41% to 108% of the amount stated on the label. Even when the weight of the sulfate molecule was included, 11 of the 14 products contained less than the amount of glucosamine stated on the label. Some manufacturers may include the weight of the stabilizing salts (NaCl or KCl) in the total weight of the product, without stating so on the label.
A few trials have evaluated glucosamine hydrochloride (GH), another form of glucosamine, as a single remedy for Osteoarthritis (OA). One trial found only minor benefits from 1,500 mg per day of GH for 8 weeks in people with OA of the knee. However, these people were also taking up to 4,000 mg per day of acetaminophen for pain relief, and that treatment might have masked a beneficial effect of GH. In another study, supplementing with GH (2,000 mg each morning for 12 weeks) significantly improved symptoms, compared with a placebo, in people with knee pain due to cartilage damage or OA. In a four-week study from China, GH was as effective as GS in people with OA of the knee. Another study found that the combination of GH and chondroitin sulfate was more effective than a placebo in people with moderate to severe knee pain from OA, but not in those with mild pain. Despite the reported beneficial effects of GH, some investigators believe that the sulfate component of GS itself helps relieve OA, and that GS would therefore be more effective than GH.
Another form of glucosamine, N-acetyl-glucosamine (NAG), has not been studied in people with osteoarthritis.
How much is usually taken?
Are there any side effects or interactions?
Animal research has raised the possibility that glucosamine could contribute to insulin resistance. This effect might theoretically result from the ability of glucosamine to interfere with an enzyme needed to regulate blood sugar levels. However, available evidence does not suggest that taking glucosamine supplements will trigger or aggravate insulin resistance or high blood sugar. Two large, three-year controlled trials found that people taking GS had either slightly lower blood glucose levels or no change in blood sugar levels, compared with people taking placebo. Until more is known, people taking glucosamine supplements for long periods may wish to have their blood sugar levels checked; people with diabetes should consult with a doctor before taking glucosamine and should have blood sugar levels monitored if they are taking glucosamine.
In 1999 the first case of an allergic reaction to oral GS was reported. Allergic reactions to this supplement appear to be rare.
Some GS is processed with sodium chloride (table salt), which is restricted in some diets (particularly for people with high blood pressure).
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