CONSUMPTION OF GREEN OR BLACK TEA DOES NOT INCREASE RESISTANCE OF LOW-DENSITY-LIPOPROTEIN TO OXIDATION IN HUMANS

Epidemiologic studies indicated that tea consumption reduces the risk of cardiovascular disease. We assessed the effect of green or black te a consumption on resistance of low-density lipoprotein (LDL) to oxidat ion ex vivo and on serum lipid concentrations in healthy volunteers. I n a 4-wk parallel comparison trial, 45 volunteers consumed 900 mL (6 c ups) mineral water, green tea, or black tea/d. Blood samples drawn whi le subjects were fasting were obtained before and after the study. The effect on resistance of subsequently isolated LDL to oxidation of add ing green or black tea extract to plasma was investigated in an in vit ro experiment. Consumption of 900 mL (6 cups) green or black tea/d did not affect serum lipid concentrations, resistance of LDL to oxidation , or markers of oxidative damage to lipids in vivo, although consumpti on of green tea slightly increased total antioxidant activity of plasm a. The in vitro experiment showed that resistance of isolated LDL to o xidation increased only after incubation of plasma with very high amou nts of green or black tea. These amounts, when converted to tea catech in concentrations, were much higher than those expected in vivo. We co nclude that daily consumption of 900 mL (6 cups) green or black tea/d for 4 wk had no effect on serum lipid concentrations or resistance of LDL to oxidation ex vivo. Future research should focus on mechanisms b y which tea flavonoids may reduce the risk of cardiovascular disease o ther than by increasing the intrinsic antioxidant status of LDL.