Caffeine is a mild alkaloid stimulant made by
some plants. It is found in coffee beans, tea leaves,
and cocao beans, added to soft drinks, energy drinks,
energy bars, and sold in capsules and tablets as a dietary
supplement. Caffeine has no nutritional value.
Caffeine is a mild stimulant. It is used to temporarily
relieve fatigue and increase mental alertness. Caffeine
is added to some antihistamine drugs to help
counteract the sleepiness they may cause.
It is also
added to over-the-counter headache remedies (e.g.,
Excedrin) and migraine headache drugs to enhance
their painkilling effects. Under medical supervision,
citrated caffeine (a prescription drug) is used to treat
breathing problems in premature infants.
Caffeine is the most widely used psychoactive
compound in the world. It has no nutritional value,
but has these effects on the body:
-increases heart rate
-temporarily increases blood pressure
-increases urine output (a diuretic)
-relaxes smooth muscle cells in the airways
-releases fatty acids and glycerol in the body for
energy use
-easily crosses the blood-brain barrier and changes
the level of neurotransmitters in the brain
-passes into breast milk
Caffeine is absorbed in the stomach. Its effects are
noticeable in about 15 minutes and usually last several
hours. However, there is huge variation among people both in their sensitivity to caffeine and in how long it
stays in their bodies.
Although the average time it
takes half a dose of caffeine to be eliminated from
the body is three to four hours, this time may extend
to six hours in women taking oral contraceptives, and
be much longer in pregnant women and in people with
liver damage.
Many well-designed, well-documented studies show
that caffeine makes people more alert, improves shortterm
memory, enhances the ability to concentrate,
increases the individual’s capacity for physical work
and speeds up reaction time.
However, caffeine achieves
this by preventing detrimental effects of withdrawal in
habitual caffeine drinkers. It does not boost functioning
to above normal levels. All these effects are temporary.
Caffeine does not replace the need for rest or sleep.
