Epidemiology studies suggest that the consumption of diets rich in flavonoids is associated with reduced risk of cardiovascular disease. Plant-derived foods and beverages, such as red wine, tea, grape and grape juice, cocoa and chocolate, can be rich in 1 particular class of flavonoid, the flavan-3-ols. There is now an increasing body of research that suggests that consuming flavanol-rich foods can positively affect hemostasis, through mechanisms that either directly affect platelet function or increase certain endothelium-derived factors that maintain platelet acquiescence or increase fibrinolysis. In this paper, we will review a series of in vivo studies on the effects of flavanol-rich cocoa and chocolate on platelet activation and platelet-dependent hemostasis. In addition, we will briefly review the body of literature with regard to other flavanol-rich foods and beverages, and possible mechanisms of action.
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Sir Ilya Arts and colleagues (Aug 7, p 488) report that chocolate and tea may contribute significantly to total dietary catechin intake (20% and 55%, respectively).
However, their methods only took into account the monomeric catechins and neglected the more abundant oligomers found in chocolate,2 which are present in only minor concentrations in tea.
Indeed, Arts and colleagues' method to determine catechin content illustrates a commonly encountered difficulty when trying to assess total dietary intake of flavonoids. The commonly used reverse-phase high-performance liquid chromatography techniques are superior for the separation of simple flavonoids, such as those found in tea. However, they are insufficient for analysis of larger oligomeric procyanidins, such as those found in cocoa and chocolate, and normal-phase chromatography is better suited.3 Adamson and colleagues have shown that the monomers (−)-epicatechin and (+)-catechin, are only a fraction of the total quantifiable procyanidins in cocoa and chocolate.4 Hence, the total concentrations of procyanidins in chocolate may have been substantially underestimated by Arts and colleagues.
