阅读理解 British scientists may have discovered the reason why red wine appears to protect the heart．They say natural chemicals found in red wine appear to protect against blocked blood vessels(血管)．The chemical substances are called poly-phenols(多酚)．They come from the outer covering of grapes．They are not present in other alcoholic drinks． Researchers say their discovery explains why many people in southern Europe can eat fatty foods and still have a low risk of heart disease．People in France, for example, have lower rates of heart disease than Americans do．Yet the traditional French diet includes butter, cheese and other foods high in cholesterol(胆固醇)．This led the British scientists to examine another important part of the French diet－red wine．Several earlier studies have suggested that people who drink proper amounts of alcohol may reduce their risk of heart disease． The British team experimented with cells from the blood vessels of cows．The scientists studied the effects of twenty-three kinds of red wine on the cow cells．They found that poly-phenols from all of the red wines stopped production of a protein called endothelin(内皮素)．This protein causes blood vessels to become smaller．Scientists believe endothelin is linked to hardening of the blood vessels, which is a cause of heart disease． The scientists found that the decrease in endothelin levels was linked to the amount of poly-phenols in the wines．The British team performed similar experiments with two other kinds of wine, white and rose．These wines contain little or no poly-phenols because the grape skins are removed before the wine is made．White and rose wines had no effect on endothelin levels． The scientists also studied the effect of non-alcoholic juice made from red grapes．They found that grape juice slowed the production of endothelin, but was much less effective than the red wines． | 
