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What is Caffeine and How Does It Affect You?

Caffeine is an addictive, potent, and quick-acting drug which produces an effect similar to the stress response in our bodes.  Caffeine affects each person differently, depending on individual circumstances such as weight, build, etc.   It has an almost instant effect on your mind-body, which will continue to influence your state for 6-8 hours afterwards.  Caffeine affects 90% of all Americans, which alters the brain's natural state, and stimulates it in a manner similar to the amphetamines cocaine and heroin.

The mechanisms employed by caffeine, cocaine, and heroin, are to close blood vessels in the brain, so the brain and body cannot sleep, to cause the release of adrenaline into the body, so the body remains active and alert, and to manipulate dopamine production in the brain, so the person experiences a temporary "high."

Caffeine may be found in its natural state in many plants, including tea leaves, coffee beans, and cocoa nuts. The pure form of caffeine is a bitter, white, crystalline powder derived from the decaffeinating process of coffee and tea. The vast number of products in which caffeine comes, range from coffee, to tea, to colas, to milk chocolate, and to pain relievers, just to mention a few.

Most people are unaware of caffeine's addictive properties; however, those who consume 300 mg. or more per day, suffer from withdrawal symptoms if they abruptly cut off their caffeine supply. Most users will suffer from symptoms of fatigue and depression, irritability, tremors, jumpiness, deprivation of deep sleep, and vascular headaches, as the blood vessels in the brain dilate. Caffeine, however, can be medically useful as a cardiac stimulant, and also as a mild diuretic used to flush the system.

One of the mechanisms that caffeine addiction, cocaine addiction, and heroin addiction share, is that they block an adenosine's ability to slow the nerve cells' activity in preparation for sleep, and instead increase the speed of their activity and of the neuron firing in the brain. The caffeine causes the blood vessels in the brain to constrict, because it has blocked the adenosine's ability to open them to allow sleep. The ability of caffeine to close the blood vessels is why many pain relievers contain caffeine. If a person has a vascular headache, the caffeine in the medicine will shut down the blood vessels, thus easing the pain.

The increased neuron firing in the brain triggers the pituitary glands to release hormones that tell the adrenal glands to produce adrenaline, also known as epinephrine. Adrenaline, the "fight-or-flight" hormone, gives the user's body a boost, and heightens the person's alertness.

One final mechanism caffeine, cocaine, and heroin share, is their ability to manipulate dopamine production. Dopamine, a neurotransmitter, activates the "pleasure centers" in certain parts of the brain, and simply makes a person feel good. Naturally, the pleasurable effect produced by dopamine manipulation plays a prominent role in caffeine addiction.

The short-term effects resulting from caffeine consumption, such as alertness, renewed energy, and pleasure, may not necessarily outweigh the longer-term effects of caffeine addiction. Caffeine, despite its similarities to amphetamines, has side effects that are not nearly as severe, and withdrawal symptoms that are, generally, not life-threatening.

How Does Caffeine Work in the Brain?

To fully understand how caffeine works a person much understand how sleep works.  The chemical adenosine accumulates in the brain when it is awake and active.  In the basal forebrain, the cells are responsible for wakeful arousal and have adenosine receptors that inhibit them.  It is as if they are moving really fast and then the adenosine attaches to them and slows them down, causing sleepiness.  They actually inhibit them by releasing a second messenger in the cell, which increases the activity of certain genes, leading to a long-lasting affect that sustains sleep for hours.  That is how sleep works.  So, how does caffeine affect adenosine and sleepiness?  Caffeine belongs to the xanthine chemical group.  Adenosine is a xanthine that is naturally occurring in the brain, used as a neurotransmitter at some synapses (gaps between nerve endings).  Because of their relation, caffeine looks a lot like adenosine to nerve cells and therefore binds to adenosine receptors in the basal forebrain.  The cells then can no longer sense adenosine because caffeine is taking up the receptors.  Instead of slowing down, the nerve cells speed up and stop the person from getting tired.   

What Are the Effects of Caffeine on the Brain?

In answering this question, this article is referring to mainly coffee drinkers.  That is how most people consume caffeine.  Adenosine reception is important to sleep, especially deep sleep.   There is a cycle that can exist when people drink coffee after a certain point in the day.  Caffeine has a half-life of 6 hours, which means that if a person drank 200mg of caffeine, 1-2 cups of coffee, at4:00pm, then at 10:00pm, 100mg of caffeine would still be in the system blocking adenosine reception.  The person may fall asleep, but would miss out on the benefits of deep sleep.  That increases tiredness the following day, also increasing the desire for coffee/caffeine.  When in this vicious cycle, some people experience splitting headaches, and many report extreme tiredness and depressed mood.  The headaches have been found to be most likely from the dilation of blood vessels in the brain.  The depressed mood is most likely just a rebound from the recent manipulation of dopamine. 

Every time you drink tea, coffee, cocoa, chocolate, or cola you are giving your body a 'hit' of caffeine. Along with nicotine and alcohol, caffeine is one of the three most widely used mood -affecting drugs in the world. If you have more than two or three caffeine drinks per day, your 'habit' may be affecting you emotionally and physically much more powerfully than you'd expect.  

What are the Effects of Caffeine? 

1. Stimulates your heart, respiratory system, and central nervous system.

2. Makes your blood more 'sludgy' by raising the level of fatty acids in the blood.

3. Causes messages to be passed along your nervous system more quickly.

4. Stimulates blood circulation.

5. Raises blood pressure.

6. Causes your stomach to produce more acid.

7. Irritates the stomach lining and gastrointestinal track.

8. Makes digestion less effective by relaxing the muscles of your intestinal system.

9. Its diuretic effect caused increased urination. 

10. Stimulates the cortex of your brain heightening the intensity of mental activity. This can result in a temporary feeling of alertness and, in the short term, banishes drowsiness and feelings of fatigue. In those who already have high levels of anxiety the heightened intensity of mental activity can produce unpleasant effects.

11. Affects the length and quality of sleep. Heavy caffeine users suffer from sleep-deprivation because their nervous system is too stimulated to allow them deep, restful or prolonged sleep.

12. The American Medical Journal has reported a correlation between caffeine and decreased bone density or osteoporosis in women.

In addition to the above effects prolonged or heavy caffeine use can produce more uncomfortable experiences:

13. Caffeine gives the nerves a jittery feeling with shaking hands, palpitations, and wobbliness in the legs.

14. Caffeine addiction which involves nervousness, irritability, agitation, headaches or ringing in the ears.

15. Causes your adrenal glands to release their hormones into your bloodstream.  

16. Causes blood sugar, or blood glucose, to be released from storage through the effects of the adrenal hormones.  This gives you a temporary lift but…

17. …requires your pancreas to over-work. This is because your pancreas now has to produce extra insulin to reduce this extra blood sugar. Once the extra insulin has 'mopped up' the extra blood sugar your temporary lift from the caffeine ends.  Your vitality level is back to normal. However in heavy caffeine users the pancreas, in time, becomes over-sensitive and over-zealous. Now it begins producing too much insulin – it 'mops up' not just the excess blood sugar but the blood sugar you need to feel alert and energetic. The initial effect of this is a let-down effect and a craving for more caffeine to give you a further boost.  A later effect can be excessive and chronic tiredness, even on waking in the morning. Some people find that many of the psychological complaints common to reactive hypoglycemia (the emotional yo-yo effect, shakiness, palpitations, weakness, tiredness, etc.) disappear within a few days of stopping caffeine.

What are Some Common Sources of Caffeine?

The richest sources of caffeine are tea, coffee, cola drinks, some over-the-counter medications, chocolate, and cocoa.  As little as 20 mgs. of caffeine can produce noticeable body and mood changes. As a very rough guide to how much caffeine you may be taking on a daily basis...  An average cup of tea contains around 50 mgs of caffeine. 

An average cup of instant coffee contains around 70-100 mgs. Instant decaffeinated coffee contains about 3 mgs.  A 6 oz cup of espresso coffee (much larger than the normal cafe cup, incidentally) contains about 80-90 mgs. A single-hit cappuccino will contain the same amount.  Filter coffee (called 'drip' in the US) can contain 25-50% more caffeine than instant.  A 340 ml or 12 oz can of regular or diet cola contains between 35 and 45 mgs. of caffeine depending on the brand.  One ounce or 28 grams of chocolate contains about 10-15 mgs .   (An average cup is about 6 UK fluid ounces or 170 ml. Your precise intake of caffeine will, of course, vary with the strength of the drink. One person's mug of instant coffee might have 75 mgs while another person might prepare a 200 mgs hit!)



Caffeine (milligrams)


Espresso coffee, brewed, 8 fluid ounces


Coffee, brewed, 8 fluid ounces


Coffee, instant, 8 fluid ounces


Coffee, brewed, decaffeinated, 8 fluid ounces


Coffee, instant, decaffeinated, 8 fluid ounces



Tea, brewed, 8 fluid ounces


Tea, herbal, brewed, 8 fluid ounces


Tea, instant, 8 fluid ounces


Tea, brewed, decaffeinated, 8 fluid ounces


Chocolate Beverages

Hot chocolate, 8 fluid ounces


Chocolate milk, 8 fluid ounces


Soft Drinks

Cola, 12 ounce can


Cola, with higher caffeine, 12 ounce can


Cola or pepper-type, diet, 12 ounce can


Cola or pepper-type, regular or diet, without caffeine, 12 ounce can


Lemon-lime soda, regular or diet, 12 ounce can


Lemon-lime soda, with caffeine, 12 ounce can


Ginger ale, regular or diet, 12 ounce can


Root beer, regular or diet, 12 ounce can



Milk chocolate bar, 1.55 ounces


M & M milk chocolate candies, 1.69 ounces


Dark chocolate, semisweet, 1 ounce


SOURCE: U.S. Department of Agriculture National Nutrient Database for Standard Reference, Release 16 July 2003.


What are the Caffeine Withdrawal Symptoms?

Physical and/or psychological addiction to caffeine is common and withdrawal symptoms usually can occur 6-18 hours after suddenly stopping caffeine intake.

Withdrawal effects vary considerably from one person to another and can include headaches, drowsiness, lethargy, irritability, trembling, restlessness, and reduced concentration.  As with any addictive drug our sensitivity to caffeine reduces with use – so we need progressively more of it to get the same hit.  To avoid uncomfortable withdrawal effects it is wise to ease off caffeine over a period of 7-14 days to reduce the discomfort. Reduce and then stop the richest sources (especially coffee) first. It is unwise, particularly if you are a heavy user, to suddenly stop caffeine altogether.  

Reducing caffeine too quickly can cause a quite dramatic drop in blood pressure, due to the body becoming over-sensitive to adenosine, and this can cause more blood to gather in the head producing a migraine-like headache.  Muscle cramps, giddiness, excessive sleepiness, and lack of concentration are other common withdrawal effects from going 'cold turkey' on caffeine.  Contact us for more information on a supplement that may lessen caffeine withdrawal symptoms- Caffeine Detox.  

When you stop caffeine it is important that you allow your body to catch up on its lost rest. This takes some time.  Using caffeine to force yourself into activity is like flogging an exhausted horse.

For the first few weeks after stopping caffeine you may find that you are sleeping deeper and for longer. For this reason it is a good idea to allow yourself an extra hour per night for a few weeks, increasing this if you continue to experience lethargy in the mornings.

If you feel drowsy during the day use breathing exercises preferably out of doors, to alert yourself.

And remind yourself that the drowsiness is a sign that you are allowing your body to get back into a more normal state and that your natural energy levels will soon return once things have got back to normal after the onslaught of the caffeine regime.



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