Clinical IT Congress

The world’s primary source of caffeine is the coffee bean (the seed of the coffee plant), from which coffee is brewed. Caffeine content in coffee varies widely depending on the type of coffee bean and the method of preparation used; even beans within a given bush can show variations in concentration. In general, one serving of coffee ranges from  milligrams, for a single shot ( milliliters) of arabica-variety espresso, to about  milligrams for a cup ( milliliters) of drip coffee. Generally, dark-roast coffee has less caffeine than lighter roasts because the roasting process reduces the bean’s caffeine content. Arabica coffee normally contains less caffeine than the robusta variety. Coffee also contains trace amounts of theophylline, but no theobromine.

Tea is another common source of caffeine. Tea usually contains about half as much caffeine per serving as coffee, depending on the strength of the brew. Certain types of tea, such as black and oolong, contain somewhat more caffeine than most other teas. Tea contains small amounts of theobromine and slightly higher levels of theophylline than coffee. Preparation has a significant impact on tea, and color is a very poor indicator of caffeine content. Teas like the pale Japanese green tea gyokuro, for example, contain far more caffeine than much darker teas like lapsang souchong, which has very little.