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Caffeine
By far our most popular (and least harmful) addictive drug, caffeine is the
stimulant in coffee, tea, chocolate, and soft drinks; it is also added to
some painkillers, cold medications, weight-loss supplements, and drugs used
to promote mental alertness. Within a few minutes after caffeine is
ingested, it is absorbed from the small intestine into the bloodstream and
carried to all the body's organs It speeds the heart rate, stimulates the
central nervous system, increases the flow of urine and the production of
digestive acids, and relaxes smooth muscles, such as those that control the
blood vessels and the airways.
Although caffeine in moderation is generally harmless, sudden withdrawal can
often cause headaches, irritability, and other symptoms that vary in
severity from one person to another. For example, in some people who are
sensitive to caffeine, the substance can trigger migraine headaches, while
in others it might actually abort a migraine by relaxing the constricted
blood vessels that are causing the throbbing head pain. People with some
types of heart-valve disease are very often advised to forgo caffeine
altogether because it can provoke heart palpitations or other cardiac
arrhythmias.
Caffeine : A known performance enhancer
The stimulant in caffeine enhances mental performance by increasing
alertness and the ability to concentrate. For many people a cup of coffee
helps them "get going" in the morning, and coffee or tea breaks during the
day give them a boost when energy lags.
Athletes have long observed that one or two caffeine drinks an hour before
competition can improve performance, especially in endurance sports like
distance running. Studies confirm that 250 mg of caffeine – the amount in
two cups of strong coffee – increases endurance, presumably because caffeine
increases the body's ability to burn fat for fuel. However, while high doses
may improve performance, they can also cause side effects and any athlete
must be aware of his individual tolerance.
Potential side effects
Ingestion of caffeine late in the day can result in a sleepless night, and
excessive intake can led to caffeinism, a syndrome marked by insomnia,
feelings of anxiety and irritability, a rapid heart-beat, tremors, and
excessive urination. These symptoms abate with the gradual withdrawal of
caffeine. Otherwise, caffeine is relatively non-toxic; a fatal adult dose of
the stimulant would require rapidly consuming the amount found in 80 to 100
cups of coffee.
Because caffeine, especially that in coffee, increases the production of
stomach acid, ulcer patients are often advised to limit coffee (including
decaffeinated) consumption to one cup after a meal. Many ulcer patients can
tolerate tea, however.
Caffeine can prompt a modest temporary rise in blood pressure; it also
speeds up the heart rate. There's no need for most heart patients to
eliminate coffee or tea from their diets, but they should use it in
moderation – cardiologists generally advise no more than 400 to 450 mg of
caffeine per day. Older people with hypertension may be more sensitive to
caffeine and should limit their intake to one cup per day.
The safety of caffeine consumption during pregnancy is controversial. Some
studies suggest that drinking one or two cups of coffee each day is
associated with a very small increase in risk of miscarriage and
low-birth-weight babies but others do not. There is stronger evidence that
drinking large amounts of caffeine daily during pregnancy may increase risk
of a miscarriage, preterm delivery or having a low-birth-weight baby. Some
experts suggest that women avoid coffee during pregnancy while others
recommend that pregnant women limit their daily caffeine consumption to
about 150 mg – the amount found in one-and-a-half cups of coffee – spread
over the entire day. Because caffeine enters breast milk, nursing mothers
should either skip caffeinated beverages altogether or consume them at least
3 hours before breast feeding.
Caffeine reduces calcium absorption, which can increase the risk of
osteoporosis, especially in older women. Those who are heavy coffee drinkers
should either consume more milk, low-fat yogurt, and other high-calcium
foods or consider taking calcium supplements.
Some people prefer decaffeinated coffee but worry that the decaffeination
process introduces some undesirable substances into the coffee. While the
process may be harmful to the flavor of the coffee, it is not harmful to its
drinker. Basically green coffee beans are soaked in water to extract the
caffeine. This solution is then treated with a solvent in which caffeine is
highly soluble. The solvents that are used never come into contact with the
beans themselves and in any case are readily removed. |
