Caffeine Facts


What is Caffeine?

  • Caffeine is one of the most comprehensively studied ingredients in the food supply.
  • In its pure state, it is an intensely bitter white powder.
  • Chemically, it is known as trimethylxantyhine.
  • It is an alkaloid, a nitrogen containing substance produced by leaves, beans or nuts of different plants and have potent effects on body functions.
  • Caffeine is found in coffee, tea, cocoa, chocolate, kola nuts, guarana, mate, cola drinks, pain medicines, cold remedies, certain weight loss products, energy drinks etc.
  • Caffeine is not addictive though it can be habit forming. Continued caffeine consumption can lead to tolerance.
  • Caffeine is a mild stimulant to the brain and the nervous system and can improve mental performance and heighten alertness.
  • Caffeine does not negatively affect concentration or higher mental functions. Coffee is therefore often consumed in the course of work to keep awake and alert.

The Most Common Things Containing Caffeine

  • Coffee
  • Tea
  • Chocolate
  • Cola drinks
  • Cocoa

Is Caffeine Harmful?

  • Most medical experts agree that, moderate amount of caffeine (less than 600 mg per day) is not harmful. This amount is equivalent to 4 to 6 cups of coffee per day.
  • In fact, moderate caffeine intake may help to ease fatique, drowsiness and motion sickness as well as improving mental performance and heightening alertness.
  • Caffeine overdose may cause the following symptoms viz headache, restlessness, nervousness, excitement, irritability, anxiety, diarrhoea, insomnia, diuresis and gastrointestinal complaints.
  • The LD50 (Lethal dose for 50% of the population) is estimated to be about 192 mg/kg of body mass or about 72 cups of coffee for an average built adult.
  • Pregnant mothers and children may consume up to 3 cups of coffee (300 mg of caffeine) a day without much risk.
  • When caffeine intake is stopped abruptly some individuals may experience withdrawal symptoms such as headache, fatigue, muscle ache, drowsiness etc.
  • To quit or reduce caffeine consumption, it is advisable to cut back gradually rather than going for the 'cold turkey' method.

Caffeine Metabolism

  • Unlike alcohol, effects of caffeine are short lived. It is quickly and completely removed from the brain.
  • Caffeine is rapidly absorbed from the digestive system reaching peak concentration in the blood 60 to 90 minutes of ingestion. It is metabolised in the liver by the cytochrome P450 enzyme system producing a number of metabolites and some are excreted unchanged in the urine.
  • Complete clearance of caffeine from plasma and urine is around 24 to 48 hours after last dosage. Average half life of caffeine is 4 to 5 hours but this can vary between 2 to 10 hours depending on genetic, physiological and environment factors.
  • Women metabolize caffeine about 25% faster than man. Infants metabolise caffeine very slowly.

Effects of Caffeine

  • Caffeine is thought to act in the brain by blocking adenosine receptors. Normally, adenosine when bound to nerve cell receptors slowed down nerve cell activity. Caffeine molecule, being similar to adenosine, binds to the same receptors but does not cause a slow down in cell activity. Instead it blocks the receptors and thereby adenosine action. The resulting increased nerve activity causes the release of the hormone epinephrine which in turn leads to several effects such as higher heart rate, increased blood pressure, increased blood flow to muscles, reduced blood flow to the skin and inner organs and release of glucose by the liver.
  • Caffeine also enhances the release of excitatory amino acids like glutamate and aspartate which are the main stimulatory neurotransmitter.
  • Caffeine stimulates the output of gastric acid which can aid digestion but may also worsen peptic ulcers, heart burn and indigestion.
  • Caffeine is a mild diuretic. It works on the kidney to excrete more urine.
  • However, it takes as much as 250 mg of caffeine in a single dose (Maughan & Griffin, 2001) to have any diuretic effect.
  • Caffeine in coffee will not cause dehydration as the caffeine's diuretic effect is compensated by the beaverage fluid content.
  • Small amounts of caffeine (less than 600 mg per day) are not harmful.
  • What caffeine does to you depend on:
    • how much you have
    • your weight and height
    • your general health
    • your mood
    • whether you have caffeine often
    • whether you have caffeine on its own, with food or with other drugs
  • Possible effects when you have a small amount of caffeine (< 600 mg per day):
    • you feel more awake and alert
    • your heart beats faster
    • you may urinate more
    • you feel warmer
    • your digestive system produces more acid
  • Possible effects when you have a large amount of caffeine (> 600 mg per day):
    • get headache
    • feel restless
    • feel nervous
    • become delirious (be confused, have hallucinations or be very excited)
    • find it difficult to sleep
  • Long term possible effects when you have more than 600 mg per day:
    • find it difficult to sleep
    • worry a lot
    • be depressed
    • have stomach upset
  • For people who already have heart problems or anxiety disorders as panic attacks or agoraphobia (being afraid of public places or open spaces), large amounts of caffeine (more than 600 mg per day) may make the problems worse.

Caffeine & Sports Performance

  • Caffeine pills are used by many body builders and sportsmen to enhance performance.
  • Caffeine increases the level of circulatory fatty acids and enhances fat oxidation. It is used in many weight loss products.
  • It has been used for years by runners and endurance people to enhance fatty acid metabolism.
  • It has been confirmed scientifically that caffeine can increase certain athletic performance.
  • There is reasonable evidence that coffee intake could protect against incidence of Parkinson's Disease (Ross et al 2001) probably due to caffeine's effects on dopamine levels.

Caffeine & Diseases

  • A study on 61,000 adults by a team at Tokoku University in Sendai in the north eastern part of Japan headed by Professor Ichiro Tsuji reported that people who drink more coffee a day are less likely to develop liver cancer than those who do not.
  • Study on 41,934 men from 1986 to 1998 and 84,276 women from 1980 to 1998 concluded that long term coffee consumption is associated with a statistically significant lower risk for Type 2 diabetes.
  • At this point in time, there is no evidence that caffeine is associated with heart disease, hypertension, osteoporosis or high cholesterol.
  • Caffeine enhances the rate and absorption of ergot alkaloid, a drug commonly used to relieve symptoms of migraine.
  • Caffeine in combination with an analgesics such as aspirin is widely used in the treatment of ordinary type of headache.
  • Epileptic on medications should restrict caffeine intake to 1 to 2 cups of coffee a day as caffeine may inhibit the protective activity of common anti-eplileptic drugs.

Caffeine & Sleep

  • Makes it harder to get to sleep.
  • Makes you sleep for a shorter time.
  • Shorten the amount of deep sleep you have.
  • Gives you more "dream sleep" at first, but less overall. Both sleep and dream sleep are important for proper rest.

Caffeine and Pregnancy

  • Having caffeine when you are pregnant is safe if you have normal amounts of caffeine. However, very large amounts of caffeine during pregnancy may lead to losing the baby, the baby being born too early or being born dead.
  • Doctors recommend that pregnant women have two to four cups of coffee or tea (about 200 mg of caffeine) a day.

Tolerance and Dependence

  • Anyone can develop a 'tolerance' to caffeine. Tolerance means that you need to have more of the drug to feel the same effects you used to have with lower amounts.
  • 'Dependence' on caffeine means that it takes up a lot of your thoughts, emotions and activities.
  • Not all people who take caffeine are dependent.


  • People who are dependent on caffeine may experience withdrawal symptoms if they try to stop or cut down abruptly the amount of caffeine they have. Withdrawal symptoms can include headaches, feeling angry or upset and tiredness.

Caffeine Chart

  • There is very little risk of harm if you have less than 600 mg of caffeine a day. If you are worried or stressed, or if you are pregnant, have less than 200 mg (2 to 4 cups of coffee or tea) a day.
How much caffeine ?

Instant Coffee

60-100 mg per cup

The amount of caffeine depends on how much you put in the cup.

Fresh coffee

80-350 mg per cup

The amount of caffeine depends on :

  • the type of beans (Robusta contains more caffeine than Arabica).
  • the way the coffee is made.
  • hyow strong the brew is.

Decaffeinated Coffee

2-4 mg per cup

The amount of caffeine is usually marked on the packet.


8-90 mg per cup

Caffeine content depends on how strong the brew is.

Cola Drinks

35 mg per 250ml serve

Cola drinks often contain a lot of sugar too.

Cocoa & Hot Chocolate

10-70 mg per cup

The amount of caffeine depends on strength of the brew and the other chemicals in the product.

Chocolate Bars

20-60 mg per 200 g bar 

Chocolate also contains a lot of sugar. 

Some prescription and over- the-counter medications

20-100 mg per dose

Some medicines (cough, headache and slimming products) contain caffeine.


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