Wang Cheng has the perfect remedy for athletes struggling to recover from injury during the Beijing Olympics. “Deer's penis,” she said, proferring a desiccated sample across the counter of the Tongrentang traditional Chinese medicine store in central Beijing.

“Mix it with some alcohol, take it every one or two days, and you'll soon feel better,” Ms Wang, a graduate in Chinese traditional medicine, said.

When asked what her remedy contained however, Ms Wang was stumped. Therein lies a problem for Chinese authorities anxious to avoid a doping scandal during the Olympics.

Chinese Olympic officials have advised national athletes not to take traditional remedies because some contain banned substances such as herbal ephedrine, a stimulant.

But many still take them, including Yao Ming, the nation's star basketball player, who announced in April that he would use traditional medicine to help his recovery from surgery on his ankle. Chinese scientists have studied the remedies - some based on recipes dating back hundreds of years - to find out exactly what they contain.

The Chinese Olympic Committee first published a list of remedies containing banned substances in 2005 and updated it in December. The State Food and Drug Administration ordered traditional medicine-makers in May to print a label that read “Athletes use with caution” on many products.

“In the past many accidents were caused because athletes took these herbs not knowing they could cause problems,” a spokeswoman for the administration told The Times. “The reason why we carried out this work is to realise our promise. We want to make the Beijing Olympics fair, open and clean.”

Last week China reinforced that message when Ouyang Kunpeng, its top men's backstroke swimmer, was given a life ban for testing positive for clenbuterol, a muscle-building agent. A first offence like that would carry a two-year ban usually.

“No matter how excellent an athlete is, he or she will be severely punished if they test positive,” Xinhua news agency quoted Yuan Hong, the head of the Chinese Olympic Committee anti-doping commission, as saying.

There were several doping scandals in China in the 1990s. Among those involved was Ma Junren, a coach who attributed his runners' results to turtle's blood and caterpillar fungus. Scientists who tested his formula found it to be a mixture of water and sugar, but he and six of his athletes were removed from the 2000 Olympic squad for suspected doping.

Chinese sports officials said that most athletes had now replaced the remedies with protein and vitamin supplements used by Western athletes.

But many still believe in traditional medicine, which has now been endorsed by Mr Yao.“There is no reason to dismiss it,” he told a press conference in April. “It's been used in our country for thousands of years.”

Use with care

— Traditional Chinese medicine has been developed over more than two millennia and has named and categorised more than 6,000 medicinal substances, of which 600 are used commonly

— Principal techniques include herbal medicine, acupuncture and tui na, or therapeutic massage

— Remedies include ground-up kidneys to remove toxins, turtle blood to boost circulation and animal feet to strengthen the legs. Ginseng is taken as an aid to recovery from muscle fatigue

— The Italian high jumper Antonella Bevilacqua was disqualified from the 1996 Olympics after testing positive for ephedrine, which she said was in a Chinese weight-loss medicine

Sources: en.beijing2008.cn; Association of Traditional Chinese Medicine; Times archives