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There are several forms of caffeine and it can come from coffee, tea, cola, chocolate, energy drinks etc. Caffeine is a central nervous system stimulant, having the effect of warding off drowsiness and restoring alertness. Beverages containing caffeine enjoy popularity great enough to make caffeine the world's most popular psychoactive drug. Coffee comes in at 54% of total caffeine consumed and tea at 43% with the remainder coming mostly from chocolate products.
Different sources of caffeine
Caffeine is an alkaloid found in numerous plant varieties. The most commonly used are coffee and tea.
Everyone probably knows that the world's primary source of caffeine is the coffee bean, from which coffee is brewed. Although it depends on the variety of coffee bean and the method of preparation used, in general one serving of coffee ranges from about 40 mg for a single shot of Arabica variety espresso to about 100 mg for strong drip coffee. Coffee also contains trace amounts of Theophylline, but no Theobromine.
Tea leaves is also another common source of caffeine in many cultures. Tea generally contains somewhat less caffeine per serving than coffee, depending on the strength of the brew. Tea contains small amounts of Theobromine and slightly higher levels of Theophylline than coffee.
Caffeine is also a common ingredient of soft drinks such as cola. Soft drinks typically contain about 10 mg to 50 mg of caffeine per serving. The caffeine in high energy drinks either originates from the ingredients used or is an additive derived from the product of decaffeination or from chemical synthesis.
Chocolate derived from cocoa also contains some amounts of caffeine but it is a weak stimulant, mostly due to its content of Theobromine and Theophylline.
However, chocolate contains too little of these compounds in a reasonable serving to create effects in humans that are on par with coffee.