Coffee is a major source of the phenolic acid chlorogenic acid and a substantial source of trigonelline, niacin, lignans magnesium, and potassium. Several of these compounds have been shown to improve glucose metabolism in animal models. Consumption of coffee was inversely associated with the risk of type-2 diabetes in prospective cohort studies across the world. Consumption of 3 to 4 cups of coffee per day was associated with an approximately 25% lower risk of type-2 diabetes. However, direct evidence of the efficacy of coffee to reduce blood glucose and insulin resistance parameters in humans from randomized trials is still lacking. In recent small trials of short duration (up to 6 weeks) coffee consumption increased levels of the insulin-sensitizing hormone adiponectin, but did not significantly improve insulin sensitivity These results suggest that a larger longer-term trial of the effects of coffee consumption on directly measured insulin sensitivity is warranted.