Caffeine and the Brain

Caffeine also increases dopamine levels in the same way that amphetamines do (heroin and cocaine also manipulate dopamine levels by slowing down the rate of dopamine re-uptake). Dopamine is a neurotransmitter that, in certain parts of the brain, activates "reward pathways" (i.e. the pleasure center). Obviously caffeine's effect is much lower than heroin's, but it is the same mechanism. It is suspected that the dopamine connection contributes to caffeine addiction.

So you can see why your body might like caffeine in the short term, especially if you are low on sleep and need to remain active:

• Caffeine blocks adenosine reception so you feel alert.
• It injects adrenaline into the system to give you a boost.
• And it manipulates dopamine production to make you feel good.

The problem with caffeine is the longer-term effects, which tend to spiral. For example, once the adrenaline wears off, you face fatigue and depression. So what are you going to do? You take more caffeine to get the adrenaline going again. As you might imagine, having your body in a state of emergency all day long isn't very healthy, and it also makes you jumpy and irritable.

Digital Vision/Getty Images Ninety percent of Americans consume caffeine every day.

The most important long-term problem is the effect that caffeine has on sleep. Adenosine reception is important to sleep, and especially to deep sleep. The half-life of caffeine in your body is about six hours. That means that if you consume a big cup of coffee with 200 mg of caffeine in it at 3 p.m., then by 9 p.m. about 100 mg of that caffeine is still in your system. You may be able to fall asleep, but your body probably will miss out on the benefits of deep sleep. That deficit adds up fast. The next day you feel worse, so you need caffeine as soon as you get out of bed. The cycle continues day after day.

This is why 90 percent of Americans consume caffeine every day. Once you get in the cycle, you have to keep taking the drug. Even worse, if you try to stop taking caffeine, you get very tired and depressed and you get a terrible, splitting headache as blood vessels in the brain dilate. These negative effects force you to run back to caffeine even if you want to stop.

It has been said that the reason so many sodas and colas contain added caffeine is to get you hooked. In the same way that addiction to nicotine makes cigarettes such a great consumer product for the companies that produce cigarettes, added caffeine in colas causes an addiction of sorts.

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