UK Sport has warned athletes for the first time that they risk failing drugs tests if they take dietary supplements.

But it says that many sportsmen and women are already heeding advice to steer well clear of such products.

Tests carried out last year showed 94 out of 634 samples from non-hormonal dietary supplements were found to contain anabolic-androgenic steroids not listed on the label.

Footballer Jaap Stam tested positive for nandrolone

Under International Olympic Committee rules, any athlete whose urine sample contained these steroids would produce a positive test for a banned substance.

"Athletes taking supplements are doing so at their own risk and personal responsibility," said UK Sport chief executive Richard Callicott.

"I am delighted to see that this message seems to be getting through, as the number of nandrolone findings in relation to total drug tests has fallen significantly since the peak in 1999.

UK Sport has already begun working with supplement manufacturers to ensure that appropriate standards of labelling are met.

Athletes should look at suitable alternatives to taking supplements Michele Verroken director of drug-free sport at UK Sport

But Michele Verroken, director of drug-free sport at UK Sport, says athletes should avoid taking supplements all together and "eat a balanced and healthy diet" instead.

Footballer Jaap Stam, 400m runner Mark Richardson and tennis player Bohdan Ulihrach are some of the high-profile sportsmen to have tested positive for nandrolone.