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The Buzz on Caffeine
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Photo: Willie Cloete
You may not think of caffeine as a drug. It is present in the three most popular drinks in the world—coffee, tea, and cola. It is also in chocolate. Could anything that widely available be a mind-altering chemical? You bet.

To chemists, caffeine is a methylxanthine. It comes from a combination of a xanthine—a molecule used as a building block in DNA, and a methyl—a combination of a carbon atom and three hydrogen atoms that is a basic building block in molecules.

That complicated chemical structure is part of the reason why caffeine keeps you awake—caffeine mimics another chemical naturally produced by your brain called adenosine. Adenosine is produced when your cells work. The harder you work, the more adenosine is produced. Your brain has adenosine receptors. When these catch adenosine, they signal your brain to slow down. You get sleepy. The harder you work, the sleepier you get. The sleepier you get, the less you work, and your body eventually recharges its energy.

Caffeine fits these receptors better than adenosine, but is shaped differently than adenosine. Caffeine does not trigger the signal that makes you sleepy. Displacing adenosine slows the fatigue process. Caffeine does not wake you up, so much as keep you from falling asleep. It lets the brain’s natural stimulants do their jobs without adenosine interfering.

Caffeine has other effects as well. It causes the airways in your lungs and your blood vessels to increase in size. As the body breaks down caffeine it changes to theophylline—a medicine used to treat asthma.

Caffeine is also a diuretic and a laxative. Caffeine relaxes smooth muscles. This includes your colon. Drink a cup of strong coffee and you may suddenly have to go.

Caffeine also affects the absorption of other drugs. Many painkillers are 50% more effective when combined with caffeine. Some over-the-counter pain medicines contain a combination of caffeine with acetaminophen or aspirin.

Caffeine has significant side effects.

Caffeine reduces fine motor skills. Caffeine can cause the shakes. While that may not make a difference banging keys on a computer, it makes a difference if you are doing extremely delicate work with your hands. Brain surgeons avoid caffeine before operating.

If you get excitable and active after taking sugar, caffeine makes it worse. Caffeine blocks the signals that slow down the brain. You cannot slow down. Drink a couple of cans of non-caffeinated soda and you become lively enough to irritate those around you. Drink two cans of caffeinated soda and you are vibrating like a humming-bee.

Caffeine may make it difficult to sleep, even when you want to. Your body is exhausted, but your brain, sleep receptors filled with caffeine, stubbornly insists that it is not ready to rest. So you toss and turn in bed, and wake up the next morning as tired as when you went to bed.

Caffeine is habit-forming. The body compensates for caffeine’s effects by producing more adenosine receptors in the brain. Skip your daily caffeine dose, and you suddenly feel tired because the receptors more quickly get filled with adenosine. Similarly, you may feel irritable until you get your caffeine level up to what you are used to. The constriction of your blood vessels to normal reduces oxygen levels, leaving you cranky.

There are better alternatives to caffeine.  A brisk 10-minute walk can raise your energy levels without caffeine. So can avoiding fatty foods or alcohol. A large, heavy meal will make you sleepy. Simply eating regular, healthy meals will leave you more alert during the day. A good night’s sleep helps, too.

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By Mark N. Lardas, copyright 2007, Mark N. Lardas, all rights reserved. Copyright © 2007 by GraceNotes. All rights reserved. Use of this material is subject to usage guidelines.


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