Since the 1980s there have been a number of studies of glucosamine sulphate. This research has been of variable quality but it does seem to point to a positive effect.

Glucosamine may help to relieve pain in osteoarthritis of the knee. Some studies even suggest the supplement may be as good as the standard treatment used in mild to moderate arthritis, non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen.

Glucosamine also seems to be fairly safe with few worrying side effects. NSAIDs, on the other hand, carry quite a large risk of side effects, especially irritation of the stomach lining and bleeding from the gut.

Glucosamine seems to be less useful when a person has more severe pain from arthritis.

Research suggests glucosamine may have some effect in slowing the progression of arthritis (known as a chondroprotective effect) by helping to keep joint cartilage healthy.

Possible downsides

One possible extra downside is the cost - glucosamine as a nutritional supplement costs about £10 a month for treatment with the recommended dose of 1,500mg a day.

Glucosamine isn't a registered medicine, so you're able buy it in health food shops and chemists. However, the Prescription Prescribing Authority will reimburse NHS prescriptions for glucosamine. This means that, in theory, your GP can prescribe it. However, many local primary care trust formulary committees don't allow this.

This article was last medically reviewed by Dr Trisha Macnair in October 2007