With diabetes, it’s a bit of a paradox. Studies around the world consistently show that high consumption of caffeinated or decaffeinated coffee is associated with low risk of type 2 diabetes. But if you look at acute studies that just give people caffeine or caffeinated coffee, and then have them eat something rich in glucose, their sensitivity to insulin drops and their blood glucose levels are higher than expected. There isn’t any long-term data on coffee consumption and glucose control. But if people have diabetes and have trouble controlling their blood glucose, it may be beneficial for them to try switching from caffeinated to decaffeinated coffee. Making the switch from caffeinated to decaf may be better than quitting coffee altogether, because some research suggests that decaffeinated coffee actually reduces the glucose response.