I'd be extremely surprised if there are not elite athletes using insulin

Dr Rob Dawson

Reports in New Scientist say doctors are hearing increasing numbers of anecdotal reports that it is being used in other sports as well.

Dr Rob Dawson is a GP who runs a confidential needle exchange scheme for bodybuilders and sportsmen.

He says about 10% of the 450 patients he regularly sees have said they use insulin.

And he added: "It's spreading outside bodybuilding. Most get it from friends who are diabetics."

He said insulin use at the Canadian championships was "highly likely". "I'd be extremely surprised if there are not elite athletes using insulin."

Peter Sonksen, who is a specialist in the study of insulin at Guy's, King's and St Thomas' School of Medicine in London added: "If you believe the street talk, it's inevitable."

'Fuel' for athletes

Insulin can help sportsmen in two ways.

Bodybuilders use insulin alongside anabolic steroids to build muscle - the steroids help create new muscle and insulin stops it from being broken down.

Sportsmen may be getting insulin on the black market

Insulin can also help athletes' stamina by providing then with "fuel" - glycogen, which stores carbohydrate energy - by taking insulin and glucose.

But insulin can be fatal if it takes so much sugar from the blood that the brain receives too little oxygen and energy.

The reason sportsmen may be tempted is that insulin is very difficult to spot in drug tests.

The only sure-fire way would be catching people red-handed with the drug

It disappears from the body in minutes, and there is no way to distinguish it from a person's own insulin.

Ban

Since 1998, insulin has only been available on prescription in the UK, and in the same year it was also banned by the International Olympic Committee.

But sportsmen and women who are diabetic can still use the insulin they need.

Michele Verroken, head of the anti-doping programme at UK Sport, said she believed some athletes were getting hold of the substance.

She added: "One of the general concerns is that it's easily obtainable. These things are entirely feasible, and we're trying to close as many loopholes as we can."

A spokeswoman for Diabetes UK said there may be a temptation for diabetics to sell on their insulin, but said there was little they could do if that was what people wanted to do.

The research was first published in the Journal of Endocrinology.