Role of green tea in reduction of cardiovascular risk factors

Abstract

Tea is widely consumed worldwide. There is accumulating evidence that tea consumption may be associated with reduced cardiovascular risk, an association that could be attributed to its flavonoid content. Green tea, the most common type of tea consumed in Asia, contains a large amount of nonoxidized flavonoids, named catechins. Green tea consumption has been associated with reduced incidence of cardiovascular mortality, stroke, and myocardial infarction. Although there is some inconsistency in the results, large, well-designed observational studies have shown this inverse association. However, the association of green tea with coronary artery disease is less well-established. The protective effect of green tea on cardiovascular events may be mediated by beneficial effects of green tea on various classical and novel cardiovascular risk factors. There is evidence that green tea reduces total and low-density lipoprotein (LDL) cholesterol and oxidized LDL cholesterol, enhances insulin sensitivity, and may prevent development of diabetes mellitus. There is also evidence that green tea reduces oxidative stress and reverses endothelial dysfunction. Its effect on blood pressure and arterial stiffness is confounded by the presence of caffeine, which has pressor and arterial stiffening effects, although this effect is probably counterbalanced by beneficial effects of other constituents in green tea. Green tea acutely increases blood pressure more than its caffeine content; the ingredients responsible for this are not known. On the other hand, green tea has a milder acute effect on arterial stiffness than its caffeine content. Its chronic effect on blood pressure and arterial stiffness may be neutral or even beneficial.