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Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class. It is the world's most widely consumed psychoactive drug. Unlike many other psychoactive substances, it is legal and unregulated in nearly all parts of the world. There are several known mechanisms of action to explain the effects of caffeine. The most prominent is that it reversibly blocks the action of adenosine on its receptor and consequently prevents the onset of drowsiness induced by adenosine. Caffeine also stimulates certain portions of the autonomic nervous system.

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Caffeine can be found in 60 different plants and many anthropologists believe its use may date back to the Stone Age. Coffee, specifically, appeared in Africa in 6th century A.D. and was later introduced to Arabia and the rest of the east. While the Chinese drank tea at least as far back as 2700 BC. In 1573 coffee was introduced to the Europeans and tea was introduced later in 1657. Caffeine was first isolated from coffee, however, in 1820 and from tea in 1827. Today, it’s the most popular drug in the world with 90% of Americans consuming it in some form. Specifically, Americans consume 450,000,000 cups of coffee a day.

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A Web M.D. article about caffeine and some shocking news about it. Did you know caffeine is in ice cream? Or that not all energy drink companies list how much caffeine are in their drinks?

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