BLACK TEA CONSUMPTION DOES NOT PROTECT LOW-DENSITY-LIPOPROTEIN FROM OXIDATIVE MODIFICATION

Objective: To investigate the in vivo and vitro effects of black tea o n the oxidative modification of low density lipoprotein (LDL). Design: The antioxidant activity of the tea was studied in vitro by measuring the resistance of the LDL to oxidative modification in the presence o f 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 mis (50.7 +/- 5.4 mg flavo noids) of black tea and peripheral venous blood was collected at 0, 30 , 60, 90, 120 and 180 min after consumption. Secondly, to assess the e ffects 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. Results: Black tea extract increased the res istance of LDL in vitro in a concentration dependent manner. There was no significant change in total plasma antioxidant capacity or suscept ibility 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 a s a control against the black tea showed no significant difference in the total plasma antioxidant capacity or susceptibility of LDL to oxid ation between the tea and coffee groups. Serum lipids, including total cholesterol, triglycerides, LDL cholesterol and HDL cholesterol did n ot change significantly throughout the study. Conclusions: The consump tion of moderate quantities of black tea acutely or for one week does not increase plasma total antioxidant capacity or alter the susceptibi lity of LDL to oxidation. Sponsorship: This work was funded by the Dep artment of Agriculture for Northern Ireland. Descriptors: low density lipoprotein (LDL); antioxidants; tea; flavonoids.