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By T. R. Reid

Slurped in black coffee or sipped in green tea, gulped down in a soda or knocked back in a headache pill, caffeine is the world's most popular psychoactive drug.

It's hardly a coincidence that coffee and tea caught on in Europe just as the first factories were ushering in the industrial revolution. The widespread use of caffeinated drinks—replacing the ubiquitous beer—facilitated the great transformation of human economic endeavor from the farm to the factory. Boiling water to make coffee or tea helped decrease the incidence of disease among workers in crowded cities. And the caffeine in their systems kept them from falling asleep over the machinery. In a sense, caffeine is the drug that made the modern world possible. And the more modern our world gets, the more we seem to need it. Without that useful jolt of coffee—or Diet Coke or Red Bull—to get us out of bed and back to work, the 24-hour society of the developed world couldn't exist.

"For most of human existence, your pattern of sleeping and wakefulness was basically a matter of the sun and the season," explains Charles Czeisler, a neuroscientist and sleep expert at Harvard Medical School. "When the nature of work changed from a schedule built around the sun to an indoor job timed by a clock, humans had to adapt. The widespread use of caffeinated food and drink—in combination with the invention of electric light—allowed people to cope with a work schedule set by the clock, not by daylight or the natural sleep cycle."

Czeisler, who rarely consumes any caffeine, is a bundle of wide-awake energy in his white lab coat, racing around his lab at Boston's Brigham and Women's Hospital, grabbing journal articles from the shelves and digging through charts to find the key data points. "Caffeine is what's called a wake-promoting therapeutic," he says.

Scientists have developed various theories to explain caffeine's "wake-promoting" power. The consensus today focuses on the drug's interference with adenosine, a chemical in the body that acts as a natural sleeping pill. Caffeine blocks the hypnotic effect of adenosine and keeps us from falling asleep. Since caffeine has also been shown to enhance mood and increase alertness in moderate amounts, it's a potent potion for students and scholars stuck in the lab at three in the morning. Paul Erdős, the Hungarian mathematician who often worked his equations around the clock, is known for saying that "a mathematician is a machine for turning coffee into theorems."

Caffeine's ability to murder sleep also makes it a drug of choice for long-distance travelers. There are as many different jet-lag remedies as there are seats on a trans-Pacific flight. But one approach, outlined in The Caffeine Advantage by Bennett Alan Weinberg and Bonnie K. Bealer, involves abstaining from caffeine for several days before traveling, then dosing yourself with small amounts of coffee or tea on the day you arrive to stay alert—preferably out in the sunshine—until your regular bedtime in your destination. (During weeks of global travel for this article, it worked for me.)

"Caffeine helps people try to wrest control away from the human circadian rhythm that is hardwired in all of us," says Czeisler. But then a shadow crosses the doctor's sunny face, and his tone changes sharply. "On the other hand," he says solemnly, "there is a heavy, heavy price that has been paid for all this extra wakefulness." Without adequate sleep—the conventional eight hours out of each 24 is about right—the human body will not function at its best, physically, mentally, or emotionally, the doctor says. "As a society, we are tremendously sleep deprived."

In fact, the professor goes on, there is a sort of catch-22 at the heart of the modern craving for caffeine. "The principal reason that caffeine is used around the world is to promote wakefulness," Czeisler says. "But the principal reason that people need that crutch is inadequate sleep. Think about that: We use caffeine to make up for a sleep deficit that is largely the result of using caffeine."

1. Find a suitable “tag-line” for each paragraph (as in “Gremlins – Little Monsters”)
2. Highlight the very first sentence of each paragraph, with the exception of line
1-2 and line 21-25.
3. Compare your tagline with the marked sentence. What’s so special?
4. Highlight 15 words that indicate the language level (high – medium – low) of this text and
say why they do so.
5. Highlight your 7 favourite (coffee-related or not) expression in the text.


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