Black tea consumption does not protect low density lipoprotein from oxidative modification

To investigate the in vivo and in vitro effects of black tea on the oxidative modification of low density lipoprotein (LDL). The antioxidant activity of the tea was studied in vitro by measuring the resistance of the LDL to oxidative modification in the presence of copper. The effects of tea consumption in vivo were investigated in two settings. Firstly, to assess the acute effects of tea consumption, five fasting healthy subjects ingested 600 mls (50.7+/-5.4 mg flavonoids) of black tea and peripheral venous blood was collected at 0, 30, 60, 90, 120 and 180 min after consumption. Secondly, to assess the effects of chronic tea consumption, a randomised crossover trial of tea (126.8+/-13.5 mg flavonoids) and coffee consumption was carried out in ten healthy subjects. Black tea extract increased the resistance of LDL in vitro in a concentration dependent manner. There was no significant change in total plasma antioxidant capacity or susceptibility of the LDL to oxidation over the 3 h period after consumption of black tea. The four-week crossover study in which coffee was used as a control against the black tea showed no significant difference in the total plasma antioxidant capacity or susceptibility of LDL to oxidation between the tea and coffee groups. Serum lipids, including total cholesterol, triglycerides, LDL cholesterol and HDL cholesterol did not change significantly throughout the study. The consumption of moderate quantities of black tea acutely or for one week does not increase plasma total antioxidant capacity or alter the susceptibility of LDL to oxidation.