The findings lend strong support to the flurry of activity in green tea supplements, growing fast in the US and set to make a strong impact in Europe too.
Green tea, traditionally consumed in Asia, has been the focus of much research in recent years, associating its powerful antioxidant compounds with anti-cancer activity, anti-bacterial effects and heart health. But until recently, green tea extracts imported from China and India have generally been used in beverages.
In a randomized, crossover study on 30 adults, researchers from the University of California, Los Angeles compared the antioxidant effects on plasma eight hours after subjects had consumed green tea, black tea or a green tea extract supplement.
"Flavanol absorption was enhanced when tea polyphenols were administered as a green tea supplement in capsule form and led to a small but significant increase in plasma antioxidant activity compared with when tea polyphenols were consumed as black tea or green tea," they write in this month's issue of the American Journal of Clinical Nutrition (vol 80, no 6, pp1558-1564).
All three products tested provided similar amounts of the antioxdiant catechin, epigallocatechin-3-gallate.
"Our observations suggest that green tea extract supplements retain the beneficial effects of green and black tea and may be used in future chemoprevention studies to provide a large dose of tea polyphenols without the side effects of caffeine associated with green and black tea beverages," said the researchers.
A number of green tea extracts suitable for supplements have recently come onto the European market. DSM, which launched its highly purified EGCG product Teavigo last year, has recently gained approval from the Italian ministry of health for its safe use in supplements, food and cosmetics. The first supplement containing the ingredient is expected to launch early next year.
Other companies marketing extracts to supplement makers include France's Greentech and Japan-based Taiyo Kagaku with its Sunphenon range of six different green tea extracts.
Growth in green tea use by food and beverage manufacturers has boosted output from China, where overall tea production rose by 3 per cent to an estimated 791 000 tonnes of tea in 2003. Green tea accounted for a 73 per cent of this output, according to FAO figures.