Coffee and Health: Caffeine Content
The average cup of American-style coffee contains
about 100 to 150 milligrams of caffeine; a properly prepared demitasse
or single serving of espresso 80 to 120 milligrams. The average
cup of tea delivers about 40 milligrams; the average chocolate
bar about 20 to 60. A 12-ounce bottle of cola drink contains 40
to 60 milligrams, about as half as much as a cup of coffee.
The short-term effects of caffeine are well agreed
upon and widely documented. A good summary appears in The Pharmacological
Basis of Therapeutics by Dr. J. Murdoch Ritchie. On the positive
side, caffeine produces "a more rapid and clearer flow of
thought," and allays "drowsiness and fatigue. After
taking caffeine one is capable of greater sustained intellectual
effort and a more perfect association of ideas. There is also
a keener appreciation of sensory stimuli, and motor activity is
increased; typists, for example, work faster and with fewer errors."
Such effects are produced by caffeine equivalent
to the amount contained in one to two cups of coffee. According
to Dr. Ritchie the same dosage stimulates the body in a variety
of other ways: heart rate increases, blood vessels dilate; movement
of fluid and solid wastes through the body is promoted. All this
adds up to the beloved "lift."
On the negative side are the medical descriptions
of the familiar "coffee nerves." The heavy coffee drinker
may suffer from chronic anxiety, a sort of "coffee come-down,"
and may be restless and irritable. Insomnia and even twitching
muscles and diarrhea may be among the effects. Very large doses
of caffeine, the equivalent of about ten cups of strong coffee
drunk in a row, produce toxic effects: vomiting, fever, chills,
and mental confusion. In enormous doses caffeine is, quite literally,
deadly. The lethal dose of caffeine in humans is estimated at
about ten grams, or the equivalent of consuming 100 cups of coffee
in one sitting.