This secondary damage appears to result from disruption of the regulation of calcium levels in the brain, while creatine helps maintain the correct calcium balance.

The danger is people will see this research and think that creatine ought to be taken if they want to protect themselves

British Olympic Medical Centre

In the UK up to one million people attend hospital every year because of head injury, up to half as a result of a car accident and 15% as a result of sports.

Creatine, found naturally in meat and fish, is very widely used by both professional and amateur athletes and is credited by some with giving muscle strength and physical endurance.

The researchers speculate that footballers, boxers, rugby players and others at risk of head injury during sports may benefit from taking it.

Prophylactic use

But experts warn against athletes in contact sports using it prophylactically in a bid to avoid the effects of a brain injury.

Nick Fellows, general manager of the British Olympic Medical Centre said many people already use the supplement inappropriately.

"Some people are using too high a dose and some are using it for too long - what we find is that athletes are actually very ignorant about the basics of nutrition," he said.

"The danger is people will see this research and think that creatine ought to be taken if they want to protect themselves."

It is not possible to be sure what the long term side-effects of creatine use may be, he said.

"There is real concern about what is in some of the supplements from some of these catalogues and magazines," Dr Fellows added.

" It seems certain things are added to supplements to make them appear better so you can't be sure you are getting something that is pure - we have recently found iron tablets spiked with steroids."