Objectives: To assess the blood concentration of catechins following green or black tea ingestion and the effect of addition of milk to black tea.
Design: Twelve volunteers received a single dose of green tea, black tea and black tea with milk in a randomized cross-over design with one-week intervals. Blood samples were drawn before and up to eight hours after tea consumption.
Setting: The study was performed at the Unilever Research Vlaardingen in The Netherlands.
Subjects: Twelve healthy adult volunteers (7 females, 5 males) participated in the study. They were recruited among employees of Unilever Research Vlaardingen.
Interventions: Green tea, black tea and black tea with semi-skimmed milk (3 g tea solids each).
Results: Consumption of green tea (0.9 g total catechins) or black tea (0.3 g total catechins) resulted in a rapid increase of catechin levels in blood with an average maximum change from baseline (CVM) of 0.46 micromol/l (13%) after ingestion of green tea and 0.10 micromol/l (13%) in case of black tea. These maximum changes were reached after (mean (s.e.m.)) t=2.3 h (0.2) and t=2.2 h (0.2) for green and black tea respectively. Blood levels rapidly declined with an elimination rate (mean (CVM)) of t1/2=4.8 h (5%) for green tea and t1/2=6.9 h (8%) for black tea. Addition of milk to black tea (100 ml in 600 ml) did not significantly affect the blood catechin levels (areas under the curves (mean (CVM) of 0.53 h. micromol/l (11%) vs 0.60 h. micromol/l (9%) for black tea and black tea with milk respectively.
Conclusion: Catechins from green tea and black tea are rapidly absorbed and milk does not impair the bioavailability of tea catechins.