Glucosamine is a natural compound made from glucose and the amino acid glutamine. The body uses it to build glycosaminoglycans, long sugar chains that form part of cartilage, the smooth, rubbery tissue that cushions the ends of bones in joints. It is also found in tendons, ligaments and the fluid around joints.
Most glucosamine in supplements is extracted from the shells of shellfish such as crab, shrimp and lobster. Shellfish-free versions are also made by fermenting corn, and these suit vegetarians and people avoiding shellfish. On labels you will see glucosamine sulphate, often stabilised with potassium or sodium chloride, or glucosamine hydrochloride.
Glucosamine is one of the best-known joint supplements and is often combined with chondroitin, MSM or collagen. Researchers have studied it extensively, with mixed results. NICE does not recommend glucosamine for osteoarthritis, and it is not routinely prescribed on the NHS, though many people choose it as a food supplement as part of their joint routine.