How caffeine works

BY MARSHALL BRAIN
HowStuffWorks.com

If you are an adult in the United States, chances are that you have taken some caffeine today.

Around 90 percent of Americans consume caffeine in one form or another every single day. More than half of all American adults take more than 300 milligrams (mg) of caffeine every day, making it America's most popular drug by far.

Have you ever wondered what it is that makes caffeine so popular? What does this drug do that causes its use to be so widespread?

Caffeine is known chemically as trimethylxanthine. Medically, caffeine is a cardiac stimulant and also a mild diuretic (it increases urine production). Recreationally, caffeine provides a "boost of energy" or a feeling of heightened alertness. Many people feel as though they cannot function in the morning without the boost that caffeine gives them.

Caffeine occurs naturally in many plants, including coffee beans, tea leaves and cocoa nuts. So you find caffeine in lots of different food products. Let's look at the most common sources of caffeine for Americans.

Typical drip-brewed coffee contains 100 mg per 6-ounce cup. But who drinks a 6-ounce cup of coffee anymore? If you are buying your coffee at a coffee shop or convenience store, or drinking it at home out of a big mug or a commuter's cup, you are consuming it in 12-, 14- or 20-ounce containers. You might be getting 300 mg of caffeine with every "cup" you drink. Typical brewed tea contains 70 mg per 6-ounce cup.

More...