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2007-9-3 23:50:27 |
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In some countries such as the U.K., milk is commonly added to tea. But German scientists have found that adding milk to tea cancels the protective effects of tea against cardiovascular diseases. Early experimental and clinical studies have found that drinking tea helps protect cardiovascular diseases. The benefits are due to the presence of antioxidative polyphenols in tea. But the effect of milk used in tea has remained unknown until now. In the study, scientists from the University of Berlin's Charit¨¦ Hospital assigned 16 women half a liter of black tea, or tea with 10 percent skimmed milk added, or hot water as control. Ultrasound was used to measure the dilation of an artery in their arm before and two hours after the consumption. The "flow mediated dilation" of the artery was significantly improved by black tea compared with water while "addition of milk completely blunted the effects of tea," The scientists found. Results of further research on rat aortic rings showed that tea induced vasorelaxation and increased the activity of endothelial nitric oxide synthase by phosphorylation of the enzyme. Nitric oxide is known to promote dilation, which is good for the cardiovascular health. The scientists also found that the protective effects of tea were completely inhibited by caseins, the major proteins present in milk through formation of complexes with tea catechins. The scientists concluded that "milk counteracts the favorable health effects of tea on vascular function." The study appears online in the European Heart Journal. |
