If you can't imagine starting your day without a cup of coffee, you may have an ancient goatherd to thank. Although there are references to coffee beans' being used as money and food as early as 575 A.D., legend has it that around that same time an African goatherd noticed that his goats were particularly lively after they nibbled on berries from a Coffea tree. When the goatherd told a local holy man about the berries, the holy man boiled them to make a beverage and discovered that it kept him alert. And word spread. Today coffee is often said to be the second-most consumed beverage on the planet (after water) because of one of its main components: caffeine.
The Physical Effects of Caffeine
Also found in tea leaves, cocoa beans, kola nuts, and several other plants, caffeine revs you up by stimulating the central nervous system and increasing blood pressure. It changes the brain's chemistry by blocking the action of a neurochemical called adenosine. "Adenosine basically tells us to slow down," explains Stanley Segall, Ph.D., a professor of nutrition and food science in the department of biological sciences at Drexel University, in Philadelphia, who has studied caffeine for 40 years. When adenosine can't do its job, more neurons fire in the brain, which in turn tells the pituitary gland to release more adrenaline. Within about 15 minutes after you've ingested caffeine, your heart is beating faster, the breathing passages in your lungs have expanded, and your liver has released sugar into the bloodstream to boost your energy. Who would have thought that one little cup could bring on such a cascade of events? Caffeine can also be habit forming. If you abruptly give up your daily cup of coffee, say, you may find yourself experiencing caffeine's hallmark withdrawal symptom, a strong headache.
Still, when used in moderation, caffeine causes little harm. For healthy adults, moderate caffeine intake — up to 400 milligrams a day, or a large (16-ounce) brewed coffee plus one can of cola and one serving of chocolate ice cream — is not associated with health risks, according to a group of Canadian researchers who reviewed more than two decades' worth of caffeine-related data. "As far as habits go," says Tibor Palfai, Ph.D., a professor of psychopharmacology at Syracuse University, in New York, "it's pretty innocuous." It may even do you some good.
Caffeine is one of the most widely studied substances in the world, and scientists have learned much about its benefits — and also why some people should avoid it.
