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Caffeine effects

Short-Term Effects

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.

Long-Term Effects

So much for the short-term effects. Researchers in the last 30 years or so have tried to implicate coffee, specifically the caffeine in coffee, in heart disease, birth defects, pancreatic cancer, and a half-dozen other less publicized health problems. So far, the evidence is, at most, inconclusive. Clinical reports and studies continue to generate far more questions than answers, and for every report tentatively claiming a link between caffeine and disease, there are several others contradicting it.

If anything, the medical evidence currently is running in favor of exonerating caffeine rather than further implicating it in disease. Some evidence even points to modest long-term health benefits for coffee drinkers.

One example of the way medical establishment has tended to see-saw on caffeine, condemning on partial evidence then backing off on further evidence, is the purported connection between heavy caffeine intake by pregnant women and birth defects. In the mid-1970s, experiments indicated that the equivalent of 12 to 24 cups of coffee (or equivalent bottles of cola) per day may cause birth defects -- in rats. Although human beings metabolize caffeine differently from rats (and other researchers had questioned some of the conditions of the experiments), the United States Food and Drug Administration issued a widely publicized warning about the possible ill effects of caffeine on the fetus. Subsequently, an analysis by Harvard researchers of coffee drinking among 12,000 women early in their pregnancies failed to find a significant link between coffee intake and birth defects. The upshot of the debate? The official position, if there is one, came from a committee of the National Academy of Sciences, which recommended what common sense dictates, what this book recommends, and what coffee lovers through the ages have argued: Pregnant women, according to the NAS committee, should exercise "moderation" in their intake of caffeine.