How Caffeine works...

Or: Why you can't wake up without it...

Ever wonder why you enjoy your morning cup of brown-black coffee so much that you keep coming back for more? I mean, let's face it, coffee is an acquired taste, and it doesn't taste all that good. But oh, that rich nutty smell can make you turn right around and run for the percolator. You imbibe your daily quota and it makes cubicle existence bearable; the joys of java. If you're like me, and you drink coffee as a hobby, you may find this mildly interesting, or if you like it for it's hyperactive properties instead, you might want to read further and find out how caffeine works it's late-night magic.

The Caffeination of Society

It is widely estimated that somewhere between 80%-90% of American's consume caffeine in some form every day. If you find yourself included in that 90%, you most likely consume over 300 milligrams (mg.) of caffeine per day. I won't get into where you obtain said caffeine or how much is in various products, as those sources have been adequately treated in previous nodes:

I'm sure you can find more as well.

Caffeine is by far America's favorite drug, but I am a little curious as to how much caffeine our counterparts in England consume. Do you drink decaffeinated tea?


  • ascorbic says re caffeine: We brits drink plenty of caffeine. Lots of coffee as well as good strong high-caffeine-but-not-as-high-as-coffee tea.
  • evilrooster says re caffeine: The British do not drink decaffeinated tea as a rule. It is held to be vile, and is not readily available (unlike decaf coffee). They do drink much, much more instant coffee than Americans.

Medically, Caffeine is known as trimethylxanthine. The chemical formula is C8H10N4O2. When isolated, primarily sourced in the decaffeination process for coffee and tea, pure caffeine is found as a white powder. This powder can be extremely potent, and estimates for LD-50, or the average intake amount for overdose, is somewhere close to 10 grams.

Caffeine has a number of medical uses. Most often it is used as a cardiac stimulant or mild diuretic. Caffeine is most often used recreationally, not medically, to stay awake and/or boost energy. It is enjoyed in many forms and variations including the typical coffee, tea, soda, and chocolate.

The average cup of coffee (6 ounces) has about 100 mg of caffeine in it. If you drink coffee from Starbucks, or pretty much any other coffee store, shop, or house, you drink 12, 16, or 20-ounce servings. As you can see, it adds up fast. Think "commuter-mug" and you're looking at just one of the servings many people throw back to start their day. If you drink one 20-ounce Starbucks coffee, you have already hit the average of 300 mg. A can of Coke has roughly 50 mg per 12 ounces. Two Cokes, and one "small" (or whatever they call it) Starbucks coffee, and you've hit the average. How far over the average are you?

Caffeine is an extremely addictive drug, both physically and mentally. The physical addiction of coffee is similar, though less potent, to amphetamines, heroin, and cocaine. These narcotics have similar mechanics, when introduced to the body, as caffeine does. Generally, caffeine is a milder stimulant than amphetamines, heroin, or cocaine, but employs similar methods of stimulus.

But you already knew all of this....

Why Caffeine Makes You Happy

Caffeine is absorbed readily through the stomach and small intestine into the bloodstream. Not quite mainlining, but it passes with relative ease. The severity of the result depends on exactly how much caffeine hits your unsuspecting cranium. Your brain is the epicenter for your caffeine-induced buzz.

While you are awake, cells in your brain produce a substance called adenosine. This substance is the byproduct of cell activity in the brain, and is picked up by adenosine receptors. Adenosine bonds to these receptors in the brain and, as levels of adenosine increase, eventually causes nerve cell activity to slow down considerably. The result is drowsiness, and ultimately, sleep.

Caffeine interferes with this process. It binds to the adenosine receptors and blocks adenosine created in the brain from finding the receptors. Now your brain becomes unable to see any further adenosine produced in the brain, and your nervous system begins to speed up.

The direct results of your nervous system speeding up are usually very apparent:

  • heart beats faster
  • pupils dilate
  • increased blood flow to muscles
  • increased blood sugar
  • blood vessels in the brain constrict
  • blood vessels at the surface of the skin contract (this is why you get cold hands after drinking a lot of coffee)
  • tremors, irritability, and nervousness
  • increased respiration

Caffeine also affects headaches: Medical effects of caffeine on headaches.

Your pituitary gland sees all this increased nerve activity and wants to get a piece of the action. It starts to pump out hormones that tell the adrenal glands to start manufacturing adrenaline (epinephrine), and this causes your body to kick into a higher gear. Your body, and your brain, is now prepared to take on the world. This simulates, to a lesser extent, the "fight or flight" effect of a large adrenaline rush in response to a dangerous situation.

The last, and probably the most important effect of caffeine, is increased dopamine levels in your brain. Similar to drugs like heroin and cocaine but in smaller amounts, caffeine prevents the recycling of dopamine in the brain. This increases dopamine levels over the length of time caffeine resides in your system. Dopamine is a neurotransmitter and it causes pleasurable sensations in your brain. It is speculated that this may lead to some of the addictive properties of caffeine.

Caffeine does have some negative effects on your body. The cycle that develops with caffeine causes people to drink more as they "come down" off of their caffeine buzz. You drink more, you get more adrenaline, and you're back on top. Your body sees this as a heightened state of alert all day long. Not good over a long period of time.

Caffeine resides in the body for a half-life of 5-7 hours on average, but depends on metabolism, blood-flow, and a variety of other factors. Smokers and young children typically have a shorter caffeine half-life, while pregnant women, women taking oral contraceptives, and people with liver disease can have much longer half-lives. A pregnant woman may have a half-life for caffeine in the body between 18 and 20 hours.

It stands to reason that drinking coffee late in the day will have residual effects well into the evening. Caffeine prevents the body from entering the deepest part of sleep, and the result is sleep that is less rejuvenating than the norm. After a night of less restful snoozing, you'll go right to the coffee pot in the morning to help you cope with the foggy-head you wake with. This perpetuates the cycle, injecting your body with fun stuff like adrenaline, dopamine, and adenosine blocking goodness. Then, you crash. Somewhere around noon you get tired. You eat some food, get sleepy, and then you drink more coffee. The cycle continues, and your sleep the next night is less than beautiful. Ultimately, caffeine can prevent deep, restful, or prolonged sleep, which can lead to a cycle of increased caffeine intake.

So you see, caffeine does have some side-affects. This write-up attempts to explain the basics of why you like caffeine, and how it works it's magic. There are some health concerns that can be increased, or created with excessive caffeine intake, but that's a story for another node...