Caffeine is classified pharmacologically as a stimulant, a cousin of cocaine and amphetamines, including Adderall and other substances in the increasingly popular cognitive-improvement prescription-drug toolbox. According to one psychiatry textbook, caffeine, cocaine, and amphetamines all produce behavioral results that include “increased locomotor activity and stimulant-like discriminative stimulus effects.” In other words, not surprisingly, they pep people up. The difference between caffeine and other stimulants is, in part, a matter of degree. Like its pharmacological cousins, caffeine signals the body to release adrenaline (hence the heightened sense of energy). Caffeine also slightly raises levels of dopamine, the brain’s feel-good hormone. Cocaine and amphetamines essentially do the same thing, only they create not just a pleasant feeling but outright euphoria. Methamphetamine and crack, because they’re highly concentrated, create an even more intense feeling. But the higher a drug’s highs, the lower its lows, which is why a crack user needing a fix might rob an elderly neighbor at gunpoint while a coffee drinker might simply get snippy with co-workers.
There’s another factor at work, a more substantive difference between caffeine and related stimulants. Because the brain develops a tolerance to all of these drugs, ever-increasing quantities are required to achieve the same high. What makes caffeine more desirable, or less potentially dangerous, than other stimulants is its built-in restraining mechanism. Technically called caffeinism, it’s the state in which an overcaffeinated user hits the drug’s “dysphoric” range and is overcome by the shakes, anxiety, tension, and nausea. Caffeine, that is, is self-regulating. “That’s one of the secrets of caffeine and probably why it’s accepted worldwide,” says Roland Griffiths, professor of psychiatry and neuroscience at Johns Hopkins and the unofficial dean of caffeine researchers. “With cocaine and amphetamines, when you increase the doses, you generally get increased stimulation and well-being.” Too much cocaine makes you feel invincible; too much coffee makes you think you’re having a nervous breakdown.
Still, as with other psychoactive drugs, there’s a huge variation in how people respond to and metabolize caffeine. Just as two hits off a joint might make one person acutely paranoid while the same two hits might induce nothing more than a pizza craving in another, some people get anxious and jittery from a little caffeine while others can guzzle coffee all day with no apparent side effects. Aside from differences in body mass, no one is sure what accounts for these discrepancies. In one study, Griffiths found that some subjects perceived a buzz after ingesting the equivalent of a couple sips of coffee, while others needed almost twenty times that amount to feel anything.
Caffeine is typically flushed out of one’s system on a half-life of two to four hours, and requires five or six of those cycles to leave the body entirely, but again there are differences. Women generally metabolize caffeine faster than men. Smokers process it twice as quickly as nonsmokers do. Women taking birth-control pills metabolize it at perhaps one-third the rate that women not on the Pill do. Asians may do so more slowly than people of other races. In The World of Caffeine: The Science and Culture of the World’s Most Popular Drug, authors Bennett Alan Weinberg and Bonnie K. Bealer hypothesize that a nonsmoking Japanese man drinking his coffee with an alcoholic beverage—another slowing agent—would likely feel caffeinated “about five times longer than an Englishwoman who smoked cigarettes but did not drink or use oral contraceptives.”
New York’s first coffeehouse opened in Manhattan in 1696, and coffee drinkers have long been skeptical that the beverage could have so many welcome benefits with so few costs. In the early 1980s, a spate of negative health studies left caffeine with a particularly awful reputation. Reports linked the drug with breast lumps, pancreatic cancer, and birth defects. All of these findings were later discredited, though not before a sort of golden age of decaf came and went. Since then, considerable evidence has been compiled showing that moderate amounts of caffeine, and coffee in particular, can actually be good for you.
Studies touting newly discovered benefits of coffee and caffeine are published every few weeks. (April 8, 2008, bulletin: Caffeine may help prevent autoimmune diseases such as multiple sclerosis.) Drinking moderate amounts of coffee is believed to slash rates of Parkinson’s disease, inhibit the formation of gallstones, and ward off cirrhosis. It may help prevent Alzheimer’s. Caffeine relieves asthma symptoms by acting as a bronchodilator. Researchers who fed mice caffeinated water found that the animals were less likely to develop skin cancer. One large-scale study showed that a person’s suicide risk decreased with each cup of coffee consumed per day, up to seven cups (notably, though, eight cups or more was shown in a separate study to increase the risk substantially). Caffeine is probably not as bad a diuretic as it’s reputed to be; many nutritionists now believe that a cup of coffee hydrates people about as well as a cup of water. The doctors Mehmet Oz and Michael Roizen, authors of the popular You: The Owner’s Manual series, recommend downing 24 ounces of coffee daily. Another study showed that a serving of coffee has more antioxidants than a serving of either grape juice or blueberries.