They explain in an online edition of the American Journal of Physiology, Regulatory Integrative and Comparative Physiology that Green tea's effect on fatty acid uptake, speeding up fat breakdown, is also thought to be the reason why it helps weight loss, another area studied by the Kao researchers, and already targeted by supplement makers.

In the new experiments, on mice swimming in an adjustable-current water pool, endurance exercise performance was boosted up to 24 per cent when the mice were given green tea extract at a dose of 0.5 per cent of their weight for 10 weeks.

It increased 8 per cent with a 0.2 per cent by-weight addition to food, showing that the effect was dose-dependant.

Like the weight loss category, the sports nutrition sector is growing rapidly, significantly outpacing growth in the more traditional vitamins and minerals categories. In the UK, second only to Germany in terms of size, sports drinks and supplements grew 37 per cent in 2002 to reach a retail value of £166 million in 2003, according to Mintel.

But while sports nutrition has been characterized by innovation and become known as one of the most dynamic segments of the nutraceuticals industry, annual growth in the US market - the world's biggest is slowing - and manufacturers are under pressure to develop novel products with new ingredients.

The Kao researchers claim that green tea extract may be one such opportunity, although results have to be confirmed in human trials.

Nor do they yet not understand the precise molecular mechanism by which green tea stimulates fatty acid metabolism, although the researchers suggest the antioxidant properties of tea catechins may play a role.

Source: Diabetes In Control.com: American Journal of Physiology, Regulatory Integrative and Comparative Physiology.