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Coffee plant (Coffea arabica), with fruits. The fruits, which are used to make coffee, contain caffeine.

Caffeine is a drug (or chemical) found in plants. It can be harmful for both humans and animals if a large amount is consumed. If a person ate 10-13 grams of caffeine quickly, between 80-100 cups of coffee, it would kill them.[1]


Caffeine is the main drug that is in coffee. Coffee comes from a tree. The seeds of the tree are roasted to make coffee.

Caffeine comes from other plants as well. It is in guarana, yerba maté, cacao, and some plants used to make tea. The plants use caffeine as a pesticide. This is a chemical that kills insects if they eat the plant. It is the way the plant protects itself.

Caffeine was first extracted from cocoa beans into its purest form which is a white powder and the word originated from the German word “kaffee” and the French word “café” which both mean caffeine.[2]

It is called guaranine when it comes from the guarana plant and theine when it comes from a tea plant. It is called mateine in the mate drink. This drink is an infusion made with Yerba mate.

What caffeine is

Caffeine molecule

Caffeine is a stimulant drug. A stimulant is a drug that increases body actions like heart rate, blood pressure, and metabolism. It makes a person more awake and alert.

Caffeine also is a diuretic. This means it makes a person make more urine (the waste liquid a person makes).

The caffeine chemical is called a xanthine alkaloid. This is a group of chemicals that are stimulants. Some xanthine alkaloids (like theophylline) are used to help asthma.

What caffeine is used for

The biggest use of caffeine is as a stimulant. People drink coffee and other drinks with caffeine to stay awake.

Doctors sometimes use caffeine as a medicine. It is used for headaches (head pain). It is sometimes used to help premature (born very early) babies to breathe. The short-term risk of this treatment seems to be that the babies treated gain less weight than usual.[3]

Caffeine is sometimes given to people after a lumbar puncture. This is a test to see if someone has meningitis.

In the beginning caffeine was found to relieve hunger, so it was used for weight loss. That did not last because people were using too much. Caffeine can be a very dangerous drug when not used in the right way.

Caffeine also has medicinal properties. It is used in many over the counter medicines, such as Excedrin, Midol and Anacin. When combined with other analgesics, caffeine can help to alleviate headaches and cramps.

Problems with caffeine

Caffeine is a problem for spiders. The image above shows a spiderweb which was woven by a normal spider. The image below shows a web of a spider that had received Caffeine in an experiment

The largest problem with caffeine is addiction. This is when people get bad symptoms when they do not have the drug. When people have withdrawal (feel bad because they do not have the drug) they drink more. This makes them feel better. But if they cannot get more, they are likely to feel some of the symptoms listed below:

  • Headaches
  • Being tired or need to sleep
  • Caffeine inhibits sleep and in the long-term alters brain functions
    • Sleep deprivation leads to a weakened connectivity between the amygdala and medial prefrontal cortex which regulate mood and emotion.
      • This causes the consumer to feel irritable, tired, restlessness, and anxious.
  • Nausea (feeling like vomiting)

Caffeine can also hurt people if they drink a lot at once. If someone takes too much of a drug at once it is called an overdose. Caffeine overdose is a medical diagnosis. It is called: Caffeine-Induced Organic Mental Disorder or Caffeine Intoxication. People with this can have these symptoms:

  • Very bad feelings like:
    • Paranoia (feeling as if people are about to hurt the person)
    • Restlessness or nervousness (with the person feeling like he cannot sit down or rest)
    • Anxiety (very bad worry)
  • Muscle movements that cannot be stopped
  • Very fast heart rate
  • Abnormal heart rhythms (even heart stopping)
  • Very high blood pressure
  • Vomiting
  • Confusion (not knowing who the person is or where he/she is)

Caffeine helps for

Caffeine also has some strong advantages:[4]

How much caffeine is safe

250–300 mg of caffeine a day is a moderate amount. That is as much caffeine that is in three cups of coffee (8oz each cup). More than 750–1000 mg a day is a significant amount, but is very unlikely to kill someone. The Lethal Dose 50 of caffeine is 192 mg per kilogram, in rats. In humans, it is between 150 and 200 mg per kilogram (70-90 per pound.)

Caffeine is in many drinks and foods. This is approximate amounts of caffeine in some food and drink:

  • Brewed coffee - 40 to 220 mg in a cup
  • Instant coffee - 30 to 120 mg in a cup
  • Decaffeinated coffee (with most caffeine taken out) - 3 to 5 mg in a cup
  • Tea - 20 to 110 mg in a cup
  • Soda drinks with caffeine - 36 to 90 mg in 12 ounces. Some people think that soft drinks which are light in color do not contain caffeine. This is not always true.
  • Milk chocolate - 3 to 6 mg in an ounce
  • Bittersweet chocolate - 25 mg in an ounce

One ounce – abbreviated oz - is 30ml.

A 'cup' is 8 oz (240ml.)

Different ways to get 200mg of caffeine

Caffeine equivalents[5][6]
In general, each of the following contains approximately 200 milligrams of caffeine:


A fluid ounce is between 28 and 30 mililitres.

a. There may also be large amounts of other chemicals, similar to caffeine in Chocolate and other products of cacao. There is theobromine in cacao, for example. These substances can have effects similar to those of caffeine.

b. Most tea drunk in North America is not very strong. The figures are for this kind of tea. The tea drunk in most other places of the world is stronger; for these kinds of tea, the figures are probably too small.


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Other websites

Scientific information



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  1. "Can caffeine kill you?". 25 September 2012. 
  2. "History and Background" (in en-US). Caffeine. 2012-09-12. Retrieved 2018-11-18. 
  3. Schmidt, B; Roberts, RS, Davis, P, Doyle, LW, et al. (May 18 2006). "Caffeine therapy for apnea of prematurity". N Engl J Med 354 (20): 2112–21. 
  4. (in en-US) The Advantages and Disadvantages Of Drinking Coffee | Coffee Corner. 2017-10-26. Retrieved 2017-12-03. 
  5. "Caffeine Content of Food and Drugs". Nutrition Action Health Newsletter. Center for Science in the Public Interest. December 1996. 
  6. "Caffeine Content of Beverages, Foods, & Medications". The Vaults of Erowid. July 7 2006. 
  7. Burgower, Rachael. "The Effects of Energy Drinks on Sleep and Daily Functioning".