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.
Effects of butter and 2 types of margarine on blood lipid and lipoprotein concentrations were compared in a controlled diet study with 23 men and 23 women. Table spreads, added to a common basal diet, provided 8.3% of energy as fat. Diets averaged 34.6% of energy as fat and 15.5% as protein. Each diet was fed for 5 wk in a 3 x 3 Latin-square design. One margarine (TFA-M) approximated the average trans monoene content of trans fatty acid-containing margarines in the United States (17% trans fatty acids by dry wt). The other margarine (PUFA-M) was free of trans unsaturated fatty acids; it contained approximately twice the polyunsaturated fatty acid content of TFA-M (49% compared with 27% polyunsaturated fatty acids). The tub-type margarines had similar physical properties at ambient temperature. Fasting blood lipids and lipoproteins were determined in 2 samples taken from the subjects during the fifth week of each dietary treatment. Compared with butter, total cholesterol was 3.5% lower (P=0.009) after consumption of TFA-M and 5.4% lower (P< 0.001) after consumption of PUFA-M. Similarly, LDL cholesterol was 4.9% lower (P=0.005) and 6.7% lower (P< 0.001) after consumption of TFA-M and PUFA-M, respectively. Neither margarine differed from butter in its effect on HDL cholesterol or triacylglycerols. Thus, consumption of TFA-M or PUFA-M improved blood lipid profiles for the major lipoproteins associated with cardiovascular risk when compared with butter, with a greater improvement with PUFA-M than with TFA-M.
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