Abstract
Relative to non-drinkers, a low to moderate alcohol intake is associated with lower risk of cardiovascular and total mortality. Epidemiological studies also suggest that a low to moderate red wine consumption may protect against cardiovascular disease. Because epidemiological studies show a similar relationship for different types of alcoholic beverages, the alcohol (ethanol), at low to moderate intakes, is proposed to provide protection. However, it remains uncertain whether there is a causal link between alcohol generally or red wine specifically and cardiovascular disease. This is very difficult to explore in epidemiological studies because of the many confounding social and dietary factors, and because risk of cardiovascular disease increases substantially from moderate to very high intakes of alcohol. The other major components of red wine that have received attention as potentially cardioprotective are the flavonoids. There is mounting evidence that flavonoids and foods and beverages rich in flavonoids can make an important contribution to cardiovascular health. Fruit and vegetables, tea and cocoa are important sources of flavonoids in the human diet. The intake of these foods hasl been associated with reduced risk of cardiovascular disease in population studies. Flavonoids are potent antioxidants in vitro, but it is their ability to cause vasorelaxation that is likely to be important for any vascular health benefits. Red grapes, their skin, their seeds and the wine derived from them are rich in flavonoids. Population studies have found that higher intakes of flavonoids are associated with lower risk for cardiovascular disease. In vitro studies, studies using animal models and human intervention studies have investigated how flavonoids might contribute to reduced risk of cardiovascular disease. A variety of mechanisms and outcomes have been explored and there is now strong evidence that flavonoids can improve endothelial function. A number of human studies have been performed to investigate the in vivo effects of red wine derived flavonoids on endothelial function. The results of these studies are mixed, with several studies indicating acute improvements, while other studies suggest little benefit of regular short-term consumption of red wine flavonoids. The effects of other rich dietary sources of flavonoids, such as tea and cocoa, to improve endothelial function may also provide a guide to the potential benefits of red wine flavonoids. Results of human trials and meta-analyses of these trials suggest that tea, cocoa and flavonoid-rich fruits can improve endothelial function. Therefore there is good evidence that flavonoid-rich foods and beverages can have vascular health benefits. However, because bioactivity of different flavonoids varies, health effects cannot be generalized to all flavonoids and flavonoid-rich foods. Further studies are needed to establish any vascular health benefits of the red wine flavonoids.