CAFFEINE
Caffeine, the active ingredient in coffee, tea, soft drinks, cocoa, chocolate, and 2000 nonprescription drugs, is the world’s most consumed drug. Eighty percent of adults in the U.S. consume it daily in one form or another. Globally, tea is the world’s most popular beverage, followed by coffee and soft drinks. One cup of tea contains about half as much caffeine as a cup of coffee. A 12-ounce can of Coke or Pepsi contains about as much caffeine as a cup of tea or half a cup of coffee. See Coffee, Infectious Disease, Tea.
• Multiple Effects of Caffeine - Caffeine is not a direct stimulant, reports health researcher Stephen Braun. “Instead, it works indirectly by interfering with one of the brain’s main chemical ‘brakes.’ Like a car with a sticky brake pedal, the brain speeds up because it can’t slow down.”
Metabolically, it takes the liver about 5 hours to break down half a given amount of caffeine. Absorbed quickly in the intestine, caffeine crosses all cell membranes and is rapidly diffused into the saliva, semen, breast milk, and amniotic fluid. Caffeine revs up the brain, stimulating mental focus, productivity, and physical performance.
However, in large amounts, caffeine produces the opposite effect, inhibiting neuron firing and acting as a depressant. Caffeine causes the heart to beat more rapidly, constricts some blood vessels and dilates others, and stimulates some muscles to contract and others to expand. Caffeine can curb the appetite, cause weight loss, and serve as a laxative. It increases urine production and can stress the kidneys.
While caffeine releases fat stored in cells, “caffeine may actually make it harder to eat a balanced, healthy diet.” In medical studies, it is associated with increased binge eating, premenstrual syndrome, and possible birth defects and impaired development of children. Decaf, meanwhile, is weakly linked with raising cholesterol, and the solvent processing method, using strong chemicals like methylene chloride or ethyl acetate, may pose risks, though it has been approved by the FDA. Habitual coffee drinkers commonly suffer from withdrawal symptoms, including tiredness, irritability, and grogginess in the morning before they have their first cup of coffee. Caffeine dependence, withdrawal, and addiction were not recognized until recently.
In writing his book, Braun concludes that he has become more conscious of caffeine’s strong, potentially harmful effects. While he still drinks coffee, he is more mindful and takes periodic “caffeine holidays” of one or two weeks at a time.
Source: Stephen Braun, Buzz: The Science and Lore of Alcohol and Caffeine (New York: Oxford University Press, 1996).