Potential Cardiovascular Health Applications of Flavanol-rich Cocoa
The mechanisms of vascular action following the feeding of flavanol-rich cocoa described above suggests potential for use in a variety of applications related to cardiovascular health. Recent studies by Grassi et al. and Fisher et al. provide tantalizing hints for what this potential could be. Grassi et al. utilized a cross-over design to study the effects of flavanol-rich dark chocolate and flavanol-poor white chocolate on blood pressure in 20 individuals aged between 25 and 60 years of age with untreated essential hypertension. After 15 days of flavanol-rich dark chocolate consumption, there was a significant reduction in ambulatory blood pressure (24-hour systolic blood pressure: -11.9 ┬▒ 7.7mm of mercury (Hg); 24-hour diastolic blood pressure: -8.5 ┬▒ 5.0mmHg). Improvements in insulin sensitivity and endothelial function were also demonstrated following flavanol-rich dark chocolate consumption for 15 days. These changes were not noted following the consumption of the flavanol-poor white chocolate.
The blood pressure reductions in this study were not observed by Fisher et al. in a shorter duration study of 27 healthy volunteers who drank a flavanol-rich cocoa (821mg per day) in four doses per day. After four days of flavanol-rich cocoa supplementation, blood pressure was measured and then measured again 90 minutes later following consumption of a single dose, with no significant change in blood pressure observed. In addition, low-dose N G-nitro-L-arginine-methyl ester (L-NAME), an NO synthase inhibitor, was infused on days one and five. Before cocoa administration, L-NAME caused a modest increase in systolic blood pressure from 117mmHg ┬▒ 2.3mmHg to 122mmHg ┬▒ 2.3 mmHg at 60 minutes (p=0.03) and a nonsignificant increase in diastolic blood pressure, from 68mmHg ┬▒ 2.1mmHg to 71mmHg ┬▒ 1.7mmHg. Interestingly, L-NAME caused a larger increase in systemic blood pressure following four days of flavanol-rich cocoa ingestion. Systolic blood pressure rose from 117mmHg ┬▒ 2.1mmHg to 128mmHg ┬▒ 4.0mmHg (p=0.005) and diastolic blood pressure rose from 66mmHg ┬▒ 1.8mmHg to 71mmHg ┬▒ 1.9mmHg (p=0.004). Presumably, in these healthy volunteers, baroreceptor adjustments were sufficient to minimize the influence of vasodilation induced by flavanol-rich cocoa on blood pressure.
Conclusive evidence in the form of large-scale randomized clinical trials is still lacking with respect to the ability of flavanol-rich cocoa to confer cardiovascular health benefits.