Indians has been hypothesized to be consequent to high ingestion of cocoa-rich beverages (14, 15). In keeping with this, recent studies showed that flavanols, a subclass of flavonoids that is richly represented in natural cocoa beans, increase NO production by cultured human vascular endothelial cells (16) and improve endothelium-dependent vasorelaxation (NO-dependent) in finger (2) and brachial (3) arteries of healthy humans. Because insulin sensitivity is, at least in part, dependent on NO availability, ie, on insulin-stimulated NO production (6, 7), we hypothesized that dark chocolate containing polyphenols might improve insulin sensitivity in vivo.We showed that dark chocolate but not white chocolate bars decreased fasting insulin and glucose concentrations as well as the glucose and insulin responses to the oral glucose challenge. As a direct consequence of these changes, we also showed that dark chocolate bars simultaneously decreased the well-recognized marker of insulin resistance, HOMA-IR, and increased 2 distinct indexes of insulin sensitivity, ie, the QUICKI and the ISI.