A single dose of tea with or without milk increases plasma antioxidant activity in humans

Objective: To investigate the effect of black and green tea consumption, wi th and without milk, on the plasma antioxidant activity in humans. Design: In a complete cross-over design, 21 healthy volunteers (10 male, 11 female) received a single dose of black tea, green tea (2 g tea solids in 300 ml water) or water with or without milk. Blood samples were obtained at baseline and at several time points up to 2 h post-tea drinking. Plasma wa s analysed for total catechins and antioxidant activity, using the ferric r educing ability of plasma (FRAP) assay. Results: Consumption of black tea resulted in a significant increase in pla sma antioxidant activity reaching maximal levels at about 60 min. A larger increase was observed after consumption of green tea. As anticipated from t he higher catechin concentration in green tea, the rise in plasma total cat echins was significantly higher after consumption of green tea when compare d to black tea. Addition of milk to black or green tea did nor affect the o bserved increases in plasma antioxidant activity. Conclusions: Consumption of a single dose of black or green tea induces a s ignificant rise in plasma antioxidant activity in two. Addition of milk to tea does not abolish this increase. Whether the observed increases in plasm a antioxidant activity after a single dose of tea prevent in vivo oxidative damage remains to be established.