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Supplements prescribed to thousands of Britons suffering from arthritis have no effect, researchers have said.
Glucosamine and chondroitin are given out on NHS prescription or bought over the counter by patients to alleviate symptoms of osteoarthritis.
This is the most common type of arthritis in the UK and mostly occurs in the knees and hips.
Today, experts writing online in the British Medical Journal (BMJ) said their review of existing research concluded the supplements are not effective.
They examined 10 existing studies and found no evidence of improvement when supplements were taken alone or in combination.
More than 3,800 patients suffering from osteoarthritis in their hips, knees or both joints took part in the studies.
Patients were typically aged 58 to 66 and had suffered symptoms for between six months and 10 years.
The results showed the supplements had no effect on joint pain or on the degree of narrowing between joints. Narrowing joint space indicates cartilage loss and worsening osteoarthritis.
However, the authors, led by Professor Peter Juni at the University of Bern in Switzerland, said some patients did think the supplements helped them.
Both glucosamine and chondroitin are available on the NHS, with 907,400 prescriptions issued in England in 2009. Many more doses of the supplements are bought over the counter by patients.
This is despite guidance from the National Institute for Health and Clinical Excellence (Nice) saying neither supplement is backed by clinical evidence.
Copyright Press Association 2010