Dark Chocolate Improves Insulin Sensitivity/Resistance and Blood Pressure
Dark Chocolate Improves Insulin Sensitivity/Resistance and Blood Pressure
March 22
Diabetes In Control

It is probably the flavanols and procyanidins contained in the dark chocolate and not white chocolate that is associated with the observed health effects.

"Numerous studies indicate that flavanols may exert significant vascular protection because of their antioxidant properties and increased nitric oxide bioavailability," write Davide Grassi, from the University of L'Aquila in Italy, and colleagues. "In turn, nitric oxide bioavailability deeply influences insulin-stimulated glucose uptake and vascular tone. Thus, flavanols may also exert positive metabolic and pressor effects."

After a seven-day cocoa-free run-in phase, 15 healthy participants were randomized to receive either dark chocolate bars or white chocolate bars for 15 days, followed by another seven-day cocoa-free washout phase and then crossover to the other chocolate. The dark chocolate bars weighed 100 g and contained approximately 500 mg polyphenols; the white chocolate bars weighed 90 g and presumably contained no polyphenols. At the end of each period, oral glucose tolerance tests were performed to calculate the homeostasis model assessment of insulin resistance (HOMA-IR) and the quantitative insulin sensitivity check index (QUICKI).

Mean HOMA-IR was 0.94 ± 0.42 after dark chocolate ingestion and 1.72 ± 0.62 after white chocolate ingestion (P < .001). Mean QUICKI was 0.398 ± 0.039 vs 0.356 ± 0.023, respectively (P = .001). Systolic blood pressure was lower after dark than after white chocolate ingestion (107.5 ± 8.6 vs 113.9 ± 8.4 mm Hg; P < .05).

"Dark, but not white, chocolate decreases blood pressure and improves insulin sensitivity in healthy persons," the authors write. "These findings indicate that dark chocolate may exert a protective action on the vascular endothelium also by improving insulin sensitivity. Obviously, large scale trials are needed to confirm these protective actions of dark chocolate or other flavanol-containing foods in populations affected by insulin-resistant conditions such as essential hypertension and obesity."
Am J Clin Nutr. 2005;81:541-542, 611-614

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Steve Freed
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