Caffeine is a naturally occurring drug belonging to a group of compounds called alkaloids. It has a molecular weight of 194.19 and is composed of carbon, hydrogen, nitrogen, and oxygen. It is found in tea leaves, coffee beans, guarana paste, and cola nuts. Caffeine is the most widely used, non-medicinal stimulant worldwide and has been a staple of the human diet for centuries. While some studies have indicated that caffeine may have deleterious health effects, no definitive conclusions have suggested moderate amounts are harmful.

The first evidence of caffeine use is from Aztec records during the time of the leader Montezuma. This civilization consumed caffeine in a hot drink made from cacao leaves. Later cultures drank caffeine in the form of coffee. Coffee was first introduced as a medicine in England, but it became a fashionable beverage between 1670 and 1730. While humans have consumed caffeine for thousands of years, it...