Short-term administration of dark chocolate is followed by a significant increase in insulin sensitivity and a decrease in blood pressure in healthy persons

Abstract

Background: Numerous studies indicate that flavanols may exert significant vascular protection because of their antioxidant properties and increased nitric oxide bioavailability. In turn, nitric oxide bioavailability deeply influences insulin-stimulated glucose uptake and vascular tone. Thus, flavanols may also exert positive metabolic and pressor effects. Objective: The objective was to compare the effects of either dark or white chocolate bars on blood pressure and glucose and insulin responses to an oral-glucose-tolerance test in healthy subjects. Design: After a 7-d cocoa-free run-in phase, 15 healthy subjects were randomly assigned to receive for 15 d either 100 g dark chocolate bars, which contained {approx} 500 mg polyphenols, or 90 g white chocolate bars, which presumably contained no polyphenols. Successively, subjects entered a further cocoa-free washout phase of 7 d and then were crossed over to the other condition. Oral-glucose-tolerance tests were performed at the end of each period to calculate the homeostasis model assessment of insulin resistance (HOMA-IR) and the quantitative insulin sensitivity check index (QUICKI); blood pressure was measured daily. Results: HOMA-IR was significantly lower after dark than after white chocolate ingestion (0.94 ± 0.42 compared with 1.72 ± 0.62; P < 0.001), and QUICKI was significantly higher after dark than after white chocolate ingestion (0.398 ± 0.039 compared with 0356 ± 0.023; P = 0.001). Although within normal values, systolic blood pressure was lower after dark than after white chocolate ingestion (107.5 ± 8.6 compared with 113.9 ± 8.4 mm Hg; P < 0.05). Conclusion: Dark, but not white, chocolate decreases blood pressure and improves insulin sensitivity in healthy persons. © 2005 American Society for Clinical Nutrition.