Davies Michael J, Judd Joseph T, Baer David J, Clevidence Beverly A, Paul David R, Edwards Alison J, Wiseman Sheila A, Muesing Richard A, Chen Shirley C
Beltsville Human Nutrition Research Center, ARS-U.S. Department of Agriculture, Beltsville, MD, USA.
J Nutr. 2003 Oct;133(10):3298S-3302S. doi: 10.1093/jn/133.10.3298S.
Despite epidemiological evidence that tea consumption is associated with the reduced risk of coronary heart disease, experimental studies designed to show that tea affects oxidative stress or blood cholesterol concentration have been unsuccessful. We assessed the effects of black tea consumption on lipid and lipoprotein concentrations in mildly hypercholesterolemic adults. Tea and other beverages were included in a carefully controlled weight-maintaining diet. Five servings/d of tea were compared with a placebo beverage in a blinded randomized crossover study (7 men and 8 women, consuming a controlled diet for 3 wk/treatment). The caffeine-free placebo was prepared to match the tea in color and taste. In a third period, caffeine was added to the placebo in an amount equal to that in the tea. Five servings/d of tea reduced total cholesterol 6.5%, LDL cholesterol 11.1%, apolipoprotein B 5% and lipoprotein(a) 16.4% compared with the placebo with added caffeine. Compared with the placebo without added caffeine, total cholesterol was reduced 3.8% and LDL cholesterol was reduced 7.5% whereas apolipoprotein B, Lp(a), HDL cholesterol, apolipoprotein A-I and triglycerides were unchanged. Plasma oxidized LDL, F2-isoprostanes, urinary 8-hydroxy-2'-deoxyguanosine, ex vivo ferric ion reducing capacity and thiobarbituric acid reactive substances in LDL were not affected by tea consumption compared with either placebo. Thus, inclusion of tea in a diet moderately low in fat reduces total and LDL cholesterol by significant amounts and may, therefore, reduce the risk of coronary heart disease. Tea consumption did not affect antioxidant status in this study.
尽管有流行病学证据表明饮茶与冠心病风险降低有关，但旨在证明茶能影响氧化应激或血液胆固醇浓度的实验研究却未取得成功。我们评估了饮用红茶对轻度高胆固醇血症成年人血脂和脂蛋白浓度的影响。茶和其他饮品被纳入精心控制的维持体重饮食中。在一项双盲随机交叉研究中，将每天饮用五份茶与一种安慰剂饮品进行比较（7名男性和8名女性，每种处理下食用控制饮食3周）。制备了不含咖啡因的安慰剂，使其在颜色和味道上与茶相匹配。在第三个阶段，向安慰剂中添加与茶中含量相等的咖啡因。与添加咖啡因的安慰剂相比，每天饮用五份茶可使总胆固醇降低6.5%，低密度脂蛋白胆固醇降低11.1%，载脂蛋白B降低5%，脂蛋白(a)降低16.4%。与未添加咖啡因的安慰剂相比，总胆固醇降低3.8%，低密度脂蛋白胆固醇降低7.5%，而载脂蛋白B、脂蛋白(a)、高密度脂蛋白胆固醇、载脂蛋白A-I和甘油三酯没有变化。与两种安慰剂相比，饮茶均未影响血浆氧化型低密度脂蛋白、F2-异前列腺素、尿8-羟基-2'-脱氧鸟苷、体外铁离子还原能力以及低密度脂蛋白中的硫代巴比妥酸反应性物质。因此，在适度低脂饮食中加入茶可显著降低总胆固醇和低密度脂蛋白胆固醇，从而可能降低冠心病风险。在本研究中，饮茶并未影响抗氧化状态。
