The answer is that it's way too many. Today, 81 calories are in every donut hole. Add that to the 2 percent of calories you'd need to eat to become full, and you're looking at 2,831 milligrams of caffeine a day. According to the Harvard University School of Public Health, half of Americans who consume excessive amounts of caffeinated beverages have an abnormal glucose level in their blood, and the risk for heart disease and stroke is increased by fourfold. Even more dangerous is the effect on your blood pressure and sugar levels. Drinking more than 1 cup of coffee a day can raise your blood pressure by as much as five points. Each teaspoon of coffee contains 43 milligrams of caffeine.