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Caffeine - Encyclopedia

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What is Caffeine?

Caffeine is a xanthine alkaloid found naturally in such foods as coffee beans, tea, kola nuts, Yerba mate, guarana berries, and (in small amounts) cacao beans. This article considers all beverages and products that contain caffeine. The English word caffeine comes from the French (Spanish and Portuguese) word for coffee: café.

Coffee beans roasted

Caffeine has been identified in over a hundred species of plant, but the most highly cultivated sources are the seeds (beans) of the berries from the coffee tree (Coffea arabica or Coffea canephora, variety robusta), the leaves and leaf-buds of the tea bush (Thea sinensis, also known as Camellia sinensis), the nut of the kola tree (Cola acuminata) and the seeds (beans) of the fruit from the cacao (cocoa) tree (Theobroma cacao). Why caffeine is found in so many plants is a matter of speculation, but a popular theory is that caffeine functions as a natural pesticide insofar as caffeine is lethally toxic for the larvae of mealworms, mosquitos and tobacco hornworms, among others.


Although tea consumption in China began thousands of years ago, the first documented use of caffeine in a beverage for its pharmacological effect was by the Sufis of Yemen, who used coffee to stay awake during prayers in the 15th century. In the 16th century, there were coffeehouses in Cairo and Mecca. Coffeehouses opened in Europe in the 17th century.

Caffeine was isolated by the German chemist Friedrich Ferdinand Runge in 1819. According to the legend, he did this at the instigation of Johann Wolfgang von Goethe (Weinberg & Bealer 2001).


Chemical name: 3,7-dihydro-1,3,7-trimethyl-1h-purine-2,6-dione.

Positive effects

Caffeine increases heartbeat, respiration, basal metabolic rate, gastroenteric reflexes, and the production of stomach acid and urine; and it relaxes smooth muscles, notably the bronchial muscle. All of these changes vary considerably among people and may depend upon the individual's sensitivity to this drug, his/her metabolism, or upon whether the consumer habitually uses or rarely uses caffeine. How long caffeine's effects last is influenced by the person's hormonal status, whether he/she smokes or takes medications, or has a disease that impairs liver functioning.

Subjectively, people report that caffeine gives them a "lift." They feel less drowsy, less fatigued, more capable of rapid and sustained intellectual effort. They also report improved performance of some manual tasks such as driving.

Negative effects

Caffeine stimulates the central nervous system and can produce a variety of effects elsewhere in the body. The symptoms of a caffeine overdose ("caffeinism") will vary, according to individual differences and the amount consumed. Doses ranging from 250 to 750 mg (2 to 7 cups of coffee) can produce restlessness, dizziness nausea, headache, tense muscles, sleep disturbances, and irregular heartbeat. Doses of over 750 mg (7 cups of coffee) can produce all of the above as well as a reaction similar to an anxiety attack, including delirium, drowsiness, ringing ears, diarrhoea, vomiting, light flashes, difficulty breathing, convulsions (extreme overdose). These amounts of caffeine may come from a single dose or from multiple doses at short intervals.


Caffeine is an alkaloid. There are numerous compounds called alkaloids, among them we have the methylxanthines, with three distinguished compounds: caffeine, theophylline, and theobromine, found in cola nuts, coffee, tea, cacao beans, mate and other plants. These compounds have different biochemical effects, and are present in different ratios in the different plant sources. These compounds are very similar and differ only by the presence of methyl groups in two positions of the chemical structure. They are easily oxidized to uric acid and other methyluric acids which are also similar in chemical structure.

Sources: Coffee, tea, cola nuts, mate, guarana.
Effects: Stimulant of the central nervous system, cardiac muscle, and respiratory system, diuretic Delays fatigue.

Sources: Tea
Effects: Cardiac stimulant, smooth muscle relaxant, diuretic, vasodilator.

Sources: Principle alkaloid of the cocoa bean (1.5-3%) Cola nuts and tea
Effects: Diuretic, smooth muscle relaxant, cardiac stimulant, vasodilator.

(Info from Merck Index)

Links / Further reading

Is Caffeine a Health Hazard?


This article is based on the following pages:

Erowids Caffeine Vault
Caffeine FAQ
Wikipedia on caffeine
Is Caffeine a Health Hazard?

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