Flavanols and their related oligomeric compounds, the procyanidins, have received increased attention during the past decade due to their reported health benefits. On the basis of compelling data published during the past decade demonstrating that the consumption of certain flavanol-rich foods can improve markers of cardiovascular health, additional clinical, and epidemiological research is clearly warranted to establish appropriate public health recommendations. However, recommendations on the consumption of these foods appropriate for use by health professionals can only be made on the basis of clinical investigations that accurately identify and quantify--through proper analytical measurement systems--the flavanols in the foods used in these investigations. This manuscript provides an overview of the strengths, weaknesses, and limitations of commonly used analytical methods to characterize the content of flavanols in foods. Two nonspecific measurements widely used by investigators, the Folin-Ciocalteu assay and the Oxygen Radical Absorbance Capacity (ORAC) measurement, are discussed in this context, as is the use of various high-performance liquid chromatography methods that provide more specific data related to the content of flavanols in foods. A comparison of the data obtained from these analytical methods to those of the more rigorous high-performance liquid chromatography analyses demonstrates that these nonspecific methods are ill-suited for providing unequivocal data necessary to evaluate the importance of dietary flavanols in the context of improving cardiovascular health. Meaningful dietary recommendations for the consumption of flavanol-rich foods will only be made possible by additional well-designed clinical and epidemiological studies enabled by detailed compositional data obtained through use of appropriate analytical methods.
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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.
Platelet activity and platelet-endothelial cell interactions are important in the acute development of thrombosis, as well as in the pathogenesis of cardiovascular disease. An increasing number of foods have been reported to have platelet-inhibitory actions, and research with a number of flavanol-rich foods, including, grape juice, cocoa and chocolate, suggests that these foods may provide some protection against thrombosis. In the present report, we review a series of in vivo studies on the effects of flavanol-rich cocoa and chocolate on platelet activation and platelet-dependent primary hemostasis. Consumption of flavanol-rich cocoa inhibited several measures of platelet activity including, epinephrine- and ADP-induced glycoprotein (GP) IIb/IIIa and P-Selectin expression, platelet microparticle formation, and epinephrine-collagen and ADP-collagen induced primary hemostasis. The epinephrine-induced inhibitory effects on GP IIb/IIIa and primary hemostasis were similar to, though less robust than those associated with the use of low dose (81 mg) aspirin. These data, coupled with information from other studies, support the concept that flavanols present in cocoa and chocolate can modulate platelet function through a multitude of pathways.
Chocolate and cocoa are extensively used in many cultures. Although their composition has been studied, the functional significance of the components has not been as well defined. There are indications that cocoa constituents exert beneficial effects on human health, and therefore cocoa and chocolate may be considered functional foods. The use of functional foods to modulate human health has gained greater significance in recent years, and chocolate is widely consumed throughout society. We performed an extensive review of literature in both animal and human systems with respect to composition, bioavailability, comparative analysis with other food products and, especially, implications for cardiovascular disease and the human immune system. Although chocolate contains a high amount of saturated fats, the two major fatty acids are palmitic and stearic acid, which appear to have fewer implications for progression of coronary artery disease than other saturated fatty acids. In addition, the implications of flavonoids and other polyphenols in chocolate as antioxidants are significant, and their ability to modulate the immune system may also be applicable to infection and neoplasia. In this review, we attempt to place these issues in perspective and to provide the reader with an extensive summary of the literature on chocolate and cocoa and their potential mechanisms of action with respect to human health.
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.
