However, experts say that it has a role in maintaining energy levels to the brain, and have the theory that taking more creatine might actually improve mental performance.

Researchers from the University of Sydney and Macquarie University, both in Australia, tested this by giving creatine supplements to 45 young adult volunteers.

Vegetarians were used for the tests, mainly because meat in the diet is in itself a source of creatine, and it would be difficult to gauge exactly how much an individual had consumed. The volunteers were split up and given either creatine or a "dummy" pill for periods of six weeks.

Their ability to repeat back from memory long sequences of numbers was tested, and a general IQ test also given to the volunteers.

The researchers, led by Dr Caroline Rae, found that the creatine supplements - at least in the short term - seemed to have a positive effect.

She said: "Both of these tests require fast brain power and the IQ test was conducted under time pressure.

"The results were clear with both our experimental groups and in both test scenarios.

"Creatine supplementation gave a significant measurable boost to brain power."

The researchers found that subjects' ability to remember long numbers improved from a number length of approximately seven digits, to an average of 8.5.

Dr Rae believes that the creatine increases the amount of energy available to the brain for computational tasks, improving general mental ability.

Health risks?

Little is known about the long-term effects of taking creatine - there are reports of effects on blood sugar balance.

The supplement is also notorious for creating an unpleasant odour in the vicinity of the taker.

There is no evidence that the mental boost would continue over time, even if the patient carried on taking creatine for months rather than weeks.

Dr Rae said: "Creatine supplementation may be of use to those requiring boosted mental performance in the short term - for example university students."

The study was published in the Royal Society journal Proceedings B.