Caffei ne is, by far, the most popular psychoactive compound consumed by humans. It exists in significant quantities in some of our favorite foods and beverages, including coffee, tea, chocolate and the soda-related kola nut. We've been downing the stuff since the Stone Age and today the average American adult consumes at least one caffeinated beverage a day. Caffeine isn't a particular dangerous substance, but it's not without its risks. It is a physically addictive stimulant that, when taken in sufficient quantities on a chronic basis, can lead to some pretty nasty health problems. There was a time when I consumed an unhealthy amount of caffeine every day and this led me to a struggle to curb my habit that lasted for two solid years. Here's the basic science and the subjective experience of caffeine addiction.

First of all, let's distinguish between the physiological and psychological aspects of caffeine addiction. The truth of the former is that it's really no big deal. Caffeine withdrawal (which we'll get to in depth later) lasts anywhere from one to five days maximum. The habits of addictive behavior can take a lot longer to beat. The physically addictive mechanism of caffeine is its role as a chemical antagonist to the neurotransmitter adenosine, the brain chemical that promotes sleep and fatigue so we don't over-exert ourselves. By more or less overcrowding adenosine with chronic overuse, caffeine forces our bodies to increase the number of adenosine receptors so we still experience the sensations necessary to get rest. When a chronic caffeine user suddenly removes the body's caffeine supply, all of those extra adenosine receptors are still active. The result is an unpleasant adjustment period of increased fatigue.

Behavioral caffeine addiction is sadly a major part of modern culture. We learn to flip on our easy-to-use coffee makers first thing in the morning. We are given free coffee and tea at work. For both lunch and dinner we mostly expect caffeinate to be part of the meal, whether it's a combo with a burger, drink and fries or another luxury with dessert. When we ask someone out on a date, what's the most common activity? Well, going out for a cup of coffee, of course. It's hard to shake the omnipresence of caffeine in our lives, though it's not impossible.

Thankfully, physical caffeine addiction isn't hard to beat, unlike more pervasive addictions like nicotine, once your body has readjusted to its pre-addicted state. You won't just tumble back into full-blown addiction with one cappuccino. You also won't be likely to court a caffeine addiction after going through withdrawal for the first time. Within 24 hours of cessation, those adenosine receptors will start doing their work. You'll feel tired, listless and generally slow-moving. The vasocronstictive properties of caffeine will become apparent when your now-relaxed blood vessels put an extra measure of fluid pressure on your cranium, resulting in a fairly nasty headache that will take a day's worth of painkiller use to combat. You may also experience joint pain for similar reasons. When all is said and done, water and juice start to look a lot more appealing.

But the real danger of caffeine abuse is in its common delivery devices. The highly acidic nature of coffee and tea can lead to stomach ulcers from chronic over-use while the phosphoric acid in soda can really wreck teeth. The best way to combat these problems is simply to treat caffeinated products like indulgences, not everyday items. There are better ways to wake up in the morning or get an energy boost in the middle of the day.