Caffeine is the world's most popular drug. The white, bitter-tasting, crystalline substance was first isolated from coffee in 1820. Both words, caffeine and coffee, are derived from the Arabic word qahweh (pronounced "kahveh" in Turkish). The origins of the words reflect the spread of the beverage into Europe via Arabia and Turkey from north-east Africa, where coffee trees were cultivated in the 6th century. Coffee began to be popular in Europe in the 17th century. By the 18th century plantations had been established in Indonesia and the West Indies.
The caffeine content of coffee beans varies according to the species of the coffee plant. Beans from Coffee arabica, grown mostly in Central and South America, contain about 1.1% caffeine. Beans from Coffee robusta, grown mostly in Indonesia and Africa, contain about 2.2% caffeine. Caffeine also occurs in cacao pods and hence in cocoa and chocolate products; in kola nuts, used in the preparation of cola drinks; and in the ilex plant, from whose leaves the popular South American beverage yerba mate is prepared.
Caffeine is also found in tea. It was first isolated from tea leaves in 1827 and named "theine" because it was believed to be a distinctly different compound from the caffeine in coffee. Tea leaves contain about 3.5% caffeine, but a cup of tea usually contains less caffeine than a cup of coffee because much less tea than coffee is used during preparation.
In North America, the caffeine content of a cup of coffee averages about 75 mg, but varies widely according to cup size, the method of preparation, and the amount of coffee used. Generally, cups prepared from instant coffee contain less caffeine (average 65 mg) and cups prepared by drip methods contain more caffeine (average 110 mg). Cups of tea average about 30 mg, but the range is also largeþfrom 10 to 90 mg.
Cola drinks contain about 35 mg caffeine per standard 280 mL serving, with some 5% of the caffeine being a component of kola nuts and most of the remainder being added in the form of a by-product of the decaffeination of coffee and tea. Caffeine- containing soft drinks account for more than 65% of soft drink consumption. A cup of hot chocolate contains about 4 mg caffeine, and a 50-gram chocolate bar between 5 and 60 mg, increasing with the quality of the chocolate. Caffeine is an ingredient of certain headache pills (30-65 mg). It is the main ingredient of non-prescription "stay-awake" pills (100-200 mg).
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