Cocoa consumption for 2 wk enhances insulin-mediated vasodilatation without improving blood pressure or insulin resistance in essential hypertension

Background: Essential hypertension is characterized by reciprocal relations between endothelial dysfunction and insulin resistance. Cocoa flavanols stimulate production of the vasodilator nitric oxide from vascular endothelium. Objective: The objective was to test the hypothesis that consumption of cocoa may simultaneously lower blood pressure, improve endothelial dysfunction, and ameliorate insulin resistance in subjects with essential hypertension. Design: We conducted a randomized, placebo-controlled, double-blind, crossover trial of a flavanol-rich cocoa drink (150 mL twice a day, approximate to 900 mg flavanols/d) in individuals with essential hypertension (n = 20). Antihypertensive medications were discontinued before study enrollment. After a 7-d cocoa-free run-in period, cocoa or flavanol-poor placebo (approximate to 28 mg flavanols/d) treatment for 2 wk was followed by a 1-wk washout and then crossover to the other treatment arm. Blood pressure was measured thrice weekly. At baseline and after each treatment period, we assessed insulin sensitivity (hyperinsulinemic-isoglycemic glucose clamp) and insulin-stimulated changes in brachial artery diameter and forearm skeletal muscle capillary recruitment (Doppler ultrasound with or without microbubble contrast). Conclusions: Daily consumption of flavanol-rich cocoa for 2 wk is not sufficient to reduce blood pressure or improve insulin resistance in human subjects with essential hypertension. This trial was registered at clinicaltrials. gov as NCT00099476. Am J Clin Nutr 2008; 88: 1685-96.