Due to antioxidant properties linked to their polyphenolic structure, dietary flavonoids are supposed to protect the organism against deleterious effects of environmental oxidants. Indeed prospective epidemiologic studies on cohorts have shown inverse correlations between consumption of some foods or beverages with high flavonoid content, (especially flavanols and anthocyanins), and coronary stroke mortality or prevalence of neurodegenerative diseases including Alzheimer's and Parkinson's diseases. These include red wine, some grape juices, red fruits, tea and cocoa, The hypothesis of cause effect relationship between dietary flavonoid intake and observed protection is further supported by several short term controlled randomised clinical trials. However composition of ingested food or beverage is complex and poorly defined, especially their content in different flavonoids. In addition, knowledge on bioavailability of these compounds and their fate in the organism is still limited. The best documented effect is protection or restoration of the vascular endothelium function, principally involving nitric oxide (*NO). It is not established that ingested flavonoids produce a direct antioxidant effect in vivo. By contrast, at the cell level, some flavonoids can modify protein kinases mediated signal transmission, thereby inducing antioxidant and anti-inflammatory genes expression, and, vice versa, inhibiting oxidant and inflammatory gene expression. Presently available information and the important health challenge justify enhanced research in the field.
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