Green Tea has become one the most popular health foods mainly because of the flavanols it contains. Both green tea and black tea contain flavanols, the most widely studied being EGCG. Studies suggest the health promoting effects of EGCG are to a large extent mediated by its antioxidant properties. One question that has not been addressed is whether supplements that contain tea extracts have the same bioavailability as the tea consumed as a liquid. This study compared the bioavailability of three types of tea: green tea, black tea, and a supplement containing green tea extract. The green and black tea were prepared with boiling water and allowed to steep for 5 minutes and the supplement was consumed as capsules. All 3 teas had the same EGCG content. Flavanol absorption was greatest with the supplement in capsule form compared to the green and black tea. The green tea supplement also resulted in greater blood antioxidant activity. The study suggests that green tea supplements are more bioavailable than green tea or black tea.

Henning SM, Niu Y, Lee NH, Thames GD, Minutti RR, Wang H, Go VL, Heber D. Bioavailability and antioxidant activity of tea flavanols after consumption of green tea, black tea, or a green tea extract supplement. Am J Clin Nutr. 2004 Dec;80(6):1558-64.