Made in the body, glucosamine is thought to be an important ingredient for both the building and repair of cartilage, ligaments, tendons and lubricating synovial fluid in the joints.
It’s available in supplements, either made from shellfish or synthetically in a laboratory, and often taken in combination with a chondroitin supplement, another component of cartilage.
Dr Sarah Brewer says: ‘Glucosamine is a popular remedy for people who develop joint symptoms such as painful knees and hips which can restrict their movement, especially if they either can’t take or tolerate non-steroidal anti-inflammatory drugs (NSAIDs). Two main types are used in supplements, glucosamine sulphate and glucosamine hydrochloride.’
What does glucosamine do?
Glucosamine is used by the body to make the building blocks of ligaments, tendons, cartilage and synovial fluid which make up a joint. Cartilage is the flexible connective tissue that cushions joints, and in osteoarthritis this becomes thinner, stiffer and flakes away. The theory is glucosamine supplements may slow this down by providing the raw materials to maintain and repair cartilage and by acting as a signal to stimulate the formation of new joint tissues.
A third of people aged over 45, a total of 8.75 million people a year in the UK, see their GP about osteoarthritis symptoms which most commonly affect the hip, knee and finger joints.
Swollen joints, creaky knees and painful hips are common symptoms of osteoarthritis. Glucosamine is often taken as a daily supplement to give relief, as it’s relatively side effect-free compared to NSAIDs such as ibuprofen, which can cause gastric upsets and stomach ulcers. Many people who can’t tolerate NSAIDs’ side effects, or who have other medical conditions which mean they are advised not to take them, choose a glucosamine supplement instead.
Although the evidence on effectiveness of glucosamine in osteoarthritis is mixed, one of the most recent trials published on patients with knee osteoarthritis concluded a combination of glucosamine hydrochloride with chondroitin, had comparable effects to celecoxib, a powerful anti-inflammatory drug, in terms of reducing pain, stiffness and joint swelling, after a six-month course, with a good safety profile.
Preventing sports injuries
Two studies on cyclists and soccer players have shown that glucosamine may prevent the wear and tear of collagen – a fibrous protein found in cartilage and other tissues – so could in theory result in less sports injuries. The results were most effective with doses of 3g a day.
Rheumatoid arthritis (RA) is an autoimmune condition where the body produces antibodies which attack the joints. One study has found that glucosamine can help reduce RA joint pain, although experts say more research is needed in this area.
Getting glucosamine from your diet
Although glucosamine is derived from shellfish and corn, it’s not possible to get enough from dietary sources alone, which is why most people take supplements instead. Supplements are made from chitin, the hard, outer shells of prawns, crabs and oysters. Synthetic supplement versions made in a laboratory are also available for people with shellfish allergies.
Most of the side effects reported with glucosamine are minor, but include wind, bloating, heartburn and skin rashes. Taking supplements with food can reduce these. In people who suffer from seafood allergies, glucosamine made from shellfish sources can trigger an allergic reaction so should be avoided.
Glucosamine can also interfere with the effects of the blood-thinning drug warfarin, so always inform your doctor.
There’s no recommended daily allowance (RDA) for glucosamine or upper safe daily limit set. A range of doses are available, either as pure glucosamine or combined with chondroitin. However, most scientific trials use a daily dose of 1,500mg – two 750mg glucosamine tablets a day is typical.
Studies show glucosamine needs to be taken for two to four months before it is effective, although you may feel the effects sooner.