van het Hof K H, de Boer H S, Wiseman S A, Lien N, Westrate J A, Tijburg L B
Unilever Research Laboratorium, Vlaardingen, Netherlands.
Am J Clin Nutr. 1997 Nov;66(5):1125-32. doi: 10.1093/ajcn/66.5.1125.
Epidemiologic studies indicated that tea consumption reduces the risk of cardiovascular disease. We assessed the effect of green or black tea consumption on resistance of low-density lipoprotein (LDL) to oxidation ex vivo and on serum lipid concentrations in healthy volunteers. In a 4-wk parallel comparison trial, 45 volunteers consumed 900 mL (6 cups) mineral water, green tea, or black tea/d. Blood samples drawn while subjects were fasting were obtained before and after the study. The effect on resistance of subsequently isolated LDL to oxidation of adding green or black tea extract to plasma was investigated in an in vitro 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 consumption of green tea slightly increased total antioxidant activity of plasma. The in vitro experiment showed that resistance of isolated LDL to oxidation increased only after incubation of plasma with very high amounts of green or black tea. These amounts, when converted to tea catechin concentrations, were much higher than those expected in vivo. We conclude 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 by which tea flavonoids may reduce the risk of cardiovascular disease other than by increasing the intrinsic antioxidant status of LDL.
流行病学研究表明，饮茶可降低心血管疾病风险。我们评估了饮用绿茶或红茶对健康志愿者体内低密度脂蛋白（LDL）氧化抗性以及血清脂质浓度的影响。在一项为期4周的平行对照试验中，45名志愿者每天饮用900毫升（6杯）矿泉水、绿茶或红茶。在研究前后采集受试者空腹时的血样。在体外实验中，研究了向血浆中添加绿茶或红茶提取物对随后分离的LDL氧化抗性的影响。每天饮用900毫升（6杯）绿茶或红茶对血清脂质浓度、LDL氧化抗性或体内脂质氧化损伤标志物均无影响，尽管饮用绿茶会使血浆总抗氧化活性略有增加。体外实验表明，只有在血浆与大量绿茶或红茶孵育后，分离的LDL氧化抗性才会增加。换算成茶儿茶素浓度后，这些量远高于体内预期值。我们得出结论，连续4周每天饮用900毫升（6杯）绿茶或红茶对血清脂质浓度或体外LDL氧化抗性没有影响。未来的研究应聚焦于茶黄酮类化合物降低心血管疾病风险的机制，而不是通过提高LDL的内在抗氧化状态。
