Chinese athletes who hope to compete in next month's London Olympics are blaming a series of humiliating performances on not being able to eat meat for fear of banned chemicals.

The coach of China's women's national volleyball team says his players have not eaten any meat for three weeks out of fear they could test positive for clenbuterol, a banned substance used to raise Chinese livestock.

The volleyball team once ranked number one in the world was soundly defeated at the World Grand Prix tournament that concluded near Shanghai on Sunday, losing three straight matches to the United States.

The coach, Yu Juemin, blamed his team's dismal performance on a lack of protein, saying his players did not have enough strength and were experiencing muscle spasms during the games.

The Communist Party-run Global Times newspaper on Tuesday said the issue “poses quite a problem” for all Chinese athletes, with the Olympic games set to begin at the end of July.

The paper quoted local reports as saying some athletic teams have even been raising their own pigs, chickens and ducks to avoid being contaminated by the illegal additive, which is banned by the International Olympic Committee.

But many on Chinese social media say the athletes' failure is no excuse for their poor performance. Others are wondering how such a commonly used additive could be considered unacceptable for athletes, but available to the general population.

Clenbuterol, a fat-burning chemical that makes pork leaner but is carcinogenic in humans, has been at the center of some of China's numerous food safety issues in recent years.

Chinese athletes fear that even a single serving of meat contaminated with clenbuterol could be enough to disqualify them from the Olympics.