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Caffeine in Your Diet

What is caffeine?

Caffeine is a stimulant that occurs naturally in tea leaves, coffee beans, cocoa beans, and several other foods. While many people enjoy the stimulating effects of caffeine, too much caffeine can cause unpleasant side effects.

How does caffeine affect the body?

Caffeine affects many parts of the body:

  • It stimulates the brain and makes you feel wide awake, energetic, and better able to concentrate.
  • It makes your heart beat faster.
  • It helps muscles to work better.
  • It aids digestion by increasing the amount of acid made by the stomach.

What happens if I have too much caffeine?

Too much caffeine can overstimulate you and result in:

  • restlessness, jumpiness, anxiety, and trouble sleeping
  • a fast or irregular heartbeat
  • twitching muscles
  • nausea
  • stomach pain.

You also can develop caffeine tolerance. This means you need more and more caffeine to get the desired effect. If you become dependent on caffeine, you have withdrawal symptoms when you go without it. You may feel tired, have a headache, or be irritable.


Caffeine may cause problems for people with these medical conditions:

  • agoraphobia (fear of being in open places)
  • anxiety or panic attacks
  • heart arrhythmias or palpitations
  • heart disease or recent heart attack (within a few weeks)
  • uncontrolled high blood pressure
  • insomnia (trouble sleeping)
  • peptic ulcer
  • premenstrual syndrome (PMS).

In the past it has been thought that caffeine can cause your body to make more urine and lose too much fluid (dehydration). However, recent research has shown that this is not true. Coffee and other caffeinated drinks like tea hydrate you just like other fluids do. If you rarely drink caffeinated drinks and suddenly drink a lot of them, you may have to urinate a bit more than if you'd had just water. But the body quickly gets used to caffeine. Regular users don't urinate any more after drinking coffee than when they drink the same amount of water.

How much caffeine is too much?

Three hundred milligrams (mg) or less of caffeine a day should not cause any problems for most people. If you drink a lot of coffee, tea, or cola, you are probably consuming a lot of caffeine.

  • The amount of caffeine in a cup of coffee depends on the amount of coffee grounds used to make it and whether it was instant or brewed. An 8-ounce cup of regular coffee may contain 75 to 120 mg of caffeine. The average cup of coffee contains 100 mg.
  • An 8-ounce cup of tea may contain 20 to 100 mg of caffeine.
  • Soft drinks have 30 to 60 mg in a 12-ounce serving.
  • Energy drinks range from 50 to 160 mg of caffeine in an 8-ounce serving. The popular large-size energy drinks (12 to 16 ounces) can contain twice as much caffeine and often are also high in calories.

The best way to see if you are getting too much caffeine is to look carefully at how it affects you. If you are having any of the symptoms of overstimulation, then you are getting too much.

Should I stop drinking beverages that contain caffeine?

Unless you are very sensitive to caffeine or have symptoms of overuse, you probably do not need to stop drinking beverages that contain caffeine. A reasonable amount of caffeine is 200 to 300 mg per day. However, if you drink enough coffee or tea to cause unpleasant symptoms, cut back or switch to drinks that are caffeine free.


Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.


HIA File diex4700.htm Release 13/2010

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