Because coffee has a naturally high concentration of caffeine, its health effects have been studied in depth. One 8 ounce cup of coffee has between 100 and 200 milligrams of caffeine, with the average being around 135. Per ounce, coffee has the single highest caffeine concentration of any naturally made beverage (excluding certain energy drinks). In this article, we’ll go in depth to figure out just what that caffeine consumption’s effects on health are.