Why Do We Love Coffee?

Name one chemical that's found in 70 percent of U.S. streams and rivers.
Some hints: It comes from dark brown liquid that's been known to scald people's tongues. Its source is often an excuse to invite someone back to your place. You probably drank it this morning, you will drink it late tonight or you've been drinking it all day and you have a cup of it next to you right now.You got it: It's caffeine, found both in the environment, and in our bodies. Ninety percent of Americans ingest some form of it every day, and its most popular liquid source is coffee; more than half of Americans drink coffee every day.Here's some information on that molecule we all know well. In its pure form, caffeine is a white, crystalline powder that's incredibly bitter.Caffeine can affect all the body's systems: Nervous, cardiovascular, respiratory, etc. And, of course, it stimulates the nervous system. One or two cups will wake a person up, making him or her feel more alert and even better able to concentrate.On the other hand, some common negative effects are higher blood pressure, increased production of urine and stomach acid, anxiety, nervousness or grumpiness.Caffeine works in the brain the same way that amphetamines, cocaine and heroin do although, obviously, caffeine is much milder. Caffeine works by mimicking a chemical in the brain called adenosine, which plays a part in sleepiness by slowing nerve cell activity in the brain. Caffeine is similar enough to adenosine to plug into the adenosine receptors in cells, but it's not similar enough to have the same effect; it doesn't slow the cells down.So it blocks the adenosine, and the brain doesn't register sleepiness. Instead, the cells speed up and more neurons fire in the brain.These effects are short-lived; they're gone as soon as caffeine leaves the body. The bad news is that once the adrenaline wears off, you can face depression and fatigue. In other words, you crash. It's this crash that keeps people going back for more coffee, and leads to addiction.So how much caffeine is in coffee, anyway? It depends on how it's brewed and from which type of beans, but regular old coffeepot coffee usually has between 80 and 118 milligrams of caffeine per five-ounce cup. The average daily coffee drinker walks around with six to 50 milligrams of caffeine in his or her bloodstream.Not only can caffeine be addictive, but people can overdose on caffeine; taking more than 250 mg at once (either by chugging a lot of coffee, or taking a caffeine pill) can lead to restlessness, nervousness, insomnia, flushed face, upset stomach, muscle twitching, rambling flow of speech and thought and irregular heartbeats.To take a lethal dose of caffeine, you'd have to ingest about 10 grams - or 100 cups of coffee - but it's easier than you'd think to get close to this dose by taking caffeine pills. True caffeine poisoning can result in tremors, nausea, vomiting, confusion, delirium, seizures and high blood sugar.So, can coffee be good for you? Definitely, if you ask the National Coffee Association. Coffee contains antioxidants, which are good for heart health and may have anti-cancer benefits. But it's not clear whether the benefits of coffee outweigh some of the negative side effects of drinking too much (like insomnia).Caffeine may have environmental effects, too; aside from its presence in rivers, a group of Norwegian scientists found trace amounts of caffeine in the bodies of Arctic sea fish. Exactly how caffeine affects the environment isn't clear, but it's a definite footprint of human presence.Given all this caffeine info can a coffee connoisseur, put down a cup? Well ... no. Because coffee is delicious; it's an important part of culture on six of the seven continents, it gives energy, at least for a short time.But being aware of coffee's effects on body and the environment does spur to think before stumble toward some coffee pot in the morning, before go for mid-afternoon top-off or for one more cup late at night to keep studying.