Epidemiological studies have indicated that regular intake of fruit and vegetables and beverages such as red wine and tea, which contain high levels of polyphenols, is associated with a reduced risk of cardiovascular diseases. The beneficial effect of polyphenol-rich natural products has been attributable, at least in part, to their direct effect on blood vessels, and in particular on endothelial cells. Indeed, polyphenols from tea, grapes, berries, and plants have been shown to activate endothelial cells to increase the formation of potent vasoprotective factors including nitric oxide (NO) and endothelium-derived hyperpolarizing factor. Experimental and clinical studies have also indicated that chronic intake of several polyphenol-rich natural products is able to improve endothelial dysfunction and to decrease vascular oxidative stress associated with major cardiovascular diseases such as hypertension. Altogether, these observations suggest that polyphenol-rich sources of natural products have the potential to improve the function of blood vessels and, hence, to protect the vascular system.
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