There may also be side effects and interactions with other drugs which this study did not address

Arthritis Research Campaign

He tested the supplement on 250 people with osteoarthritis, the most common form of the condition. Each was suffering from moderate to severe pain.

Over a six week period, some were given a 255 milligram dose of the dietary supplement twice a day. The rest were given a placebo.

Two-thirds of those given the ginger pills reported relief from pain - significantly more than those taking the placebo.

Bigger improvements

The ginger group also reported bigger improvements in their levels of pain.

Professor Altman, who is based at the University of Miami Medical School, said: "The effect is similar to that seen with trials using conventional drugs."

Arthritis is usually treated with anti-inflammatory drugs. But these can be associated with severe side effects.

A spokesperson for the Arthritis Research Campaign told BBC News Online that ginger was already taken by some arthritis patients for its mild anti-inflammatory effects.

However, she added: "Although this study is of interest to patients, it actually showed that the beneficial effects of ginger were fairly small and inconsistent.

"The study in question involved only a small number of people over a six week period, and we think a bigger trial over a much longer period of time would need to be conducted before any claims as to the reliability of the product's efficacy were taken too seriously.

"There may also be side effects and interactions with other drugs which this study did not address, and the safety of the product would also need to be assessed more fully."

Common condition

Osteoarthritis is the commonest form of joint disease.

It is generally considered to be due to "wear and tear" of the joints leading to damage of the joint surfaces which gives pain on movement.

The condition is very common in older age groups, but can affect younger people too.

There are many factors that influence its development, including a family history and previous damage to the joint through injury or surgery.

The research is published in the journal Arthritis and Rheumatism.