Cocoa Flavanols and Mechanisms of Vascular Action
Cocoa flavanols have demonstrated the potential to modulate cardiovascular health in at least two important ways: inhibition of platelet activation and improved endothelial function. Rein et al. demonstrated that flavanol-rich cocoa inhibits platelet activation ex vivo six hours following its ingestion, with significant reduction in the expression of the surface proteins glycoprotein IIb/IIIa and P-selectin.
In addition to cocoa, a subsequent study found that flavanol-rich chocolate could also inhibit platelet activation ex vivo in humans. Most recently, a 28-day study found that the consumption of cocoa flavanols reduced platelet aggregation in a group of healthy volunteers, an effect not observed in the group that consumed the matched placebo. Together, these data support the concept that the regular consumption of cocoa flavanols may reduce the activation of platelets and provide a dietary approach to reducing clot formation.
On an acute basis, Pearson et al. directly compared the acute effects of flavanol-rich cocoa and aspirin with respect to inhibition of platelet function. The magnitude of the effect induced by flavanol-rich cocoa was less than that of aspirin, but still statistically significant. Existing data suggest that the primary action of flavanol-rich cocoa with respect to platelet function is to increase the levels of the anti-aggregatory prostaglandin prostacyclin, decrease the levels of pro-aggregatory leukotrienes, and increase the levels of available nitric oxide (NO). More research is needed to determine whether flavanol-rich cocoa can affect other pathways that are important in the prevention of thrombosis.
During the mid 1990s, Hollenberg et al. validated the observation that the Kuna Indians of Panama do not experience an increase in hypertension as they age. This apparent protection was lost in the Kuna when they moved to the urban environment of Panama City. Subsequent dietary research revealed that the Kuna consume large quantities of flavanol-rich cocoa when living in their indigenous environment, but not when they move to the urban environment.This observation, coupled with in vitro research demonstrating that specific cocoa flavanols could induce aortic ring relaxation via an NO-dependent mechanism, suggested that the frequent consumption of flavanol-rich cocoa by the Kuna could be one of the protective factors against age-associated hypertension that this population enjoys.