The results, which suggest a heart-healthy benefit for the tea, add to an ever-growing body of science linking consumption to a wide range of health benefits, including lower risk of certain cancers, weight loss, and protection against Alzheimer's.
The health benefits, which have mainly focused on green tea, have been linked to the polyphenol content of the tea. Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent. Oolong tea is semi-fermented tea and is somewhere between green and black tea.
The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.
The new research, published in the current issue of the European Journal of Clinical Nutrition (Vol. 60, pp. 1330-1336), was led by Keiichi Abe from Institute for Health Care Science, Suntory Ltd, and included researchers from the University of Tokushima and Providence University, Taiwan.
The scientists recruited twelve healthy aduls (nine women, averag age 22) and randomly divided them into two groups, one to receive 38 g of fat from potato chips (19 g within 30 minutes of eating lunch and dinner) and 750 ml of a placebo- or polyphenol-enriched oolong tea at three meals in a double-blind placebo-controlled crossover design.
A seven-day washout period separated the ten-day intervention periods, and blood samples were collected after days 8, 18, 25 and 35. Three faecal samples were also collected in order to measure lipid excretion levels.
The Japanese-Taiwanese researchers report that faecal lipid excretion was significantly increased during the polyphenol-enriched oolong tea period, compared to placebo (19.3 versue 9.34 g/3day, respectively).
The polyphenol-enriched oolong tea period was also associated with a 50 per cent increase in cholesterol excretion, compared to the placebo-teat group (10.8 versus 1.2 g/3day, respectively).
High cholesterol levels, hypercholesterolaemia, have a long association with many diseases, particularly cardiovascular disease (CVD), the cause of almost 50 per cent of deaths in Europe, and reported to cost the EU economy an estimated €169bn ($202bn) per year.
"The results of this study indicated that polyphenol-enriched oolong tea could increase lipid excretion into feces when subjects took high-lipid diet," concluded the researchers.
More research with a larger study population is needed, in addition to mechanistic studies to elucidate the underlying mechanism by which the polyphenols appear to reduce fat absorption. But the results are in agreement with other studies that have linked red wine consumption, polyphenol-rich green tea or pine bark extracts to improved cardiovascular risk factors.
This study is good news for both the tea market and the tea extract market. European demand for tea extracts is currently surging, having reached 500 metric tonnes by 2003.
This has seen companies such as DSM, with its Teavigo boasting 95 per cent purity of EGCG, and Taiyo International, with its Sunphenon claiming more than 90 per cent purity, position themselves firmly in specific catechin markets.
The global tea market is worth about €790 (£540, $941) million. Green tea accounts for about 20 per cent of total global production, while black tea (green tea that has been oxidized by fermentation) accounts for about 78 per cent.