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 short-
term 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.
Caffeine is on the United States Food and Drug
Administration (FDA) list of foods generally recog-
nized as safe (GRAS list). In moderate amounts, caf-
feine does not appear to be harmful to humans,
although it is poisonous to dogs, horses, and some
birds. ‘‘Moderate’’ generally means consumption in
the rage of 300–400 mg or 3–4 cups of coffee daily.
Caffeine has not been shown to cause birth defects and
is considered safe in reasonable amounts during preg-
nancy. The March of Dimes Birth Defects Foundation
recommends that pregnant women limit their caffeine
intake to the equivalent of two cups of coffee per day,
and that women who are having difficulty becoming
pregnant eliminate caffeine from their diet.
By law, caffeine must be listed as an ingredient on
food labels, but the amount of caffeine per serving is
not required to be disclosed. Since caffeine is added to
so many products, it is difficult to the amount of
caffeine in an individual’s diet. Caffeine content of
coffees and teas varies depending on where the plants
were grown and how the beverages are prepared. The
approximate amounts of caffeine is some common
products are:
coffee, brewed 8 oz: 135 mg
coffee, decaffeinated, 8 oz: 5 mg
coffee, espresso, 1 oz: 40 mg
green tea, brewed, 8 oz: 15 mg
black tea, brewed, 8 oz: 50 mg
tea, decaffeinated, 8 oz: 4 mg
Mountain Dew, 1 can (12 oz): 55 mg
Coca-Cola Classic, 1 can (12 oz): 34 mg
Diet Coke: 1 can (12 oz) 45 mg
Pepsi Cola, 1 can (12 oz): 37 mg
Sunkist Orange, regular or diet, 1 can (12 oz): 41 mg
Barq’s Root Beer: 1 can (12 oz): 22 mgdiet Barq’s Root Beer: 1 can (12 oz): 0 mg
Sprite, diet or regular: 1 can (12 oz) 0 mg
7-Up, 1 can (12 ounces): 0 mg
Red Bull energy drink, 8.5 oz: 80 mg
Cocaine energy drink, 8.5 oz: 280 mg
SoBe No Fear energy drink, 8 oz: 80 mg
Hershey’s Special Dark chocolate, 1 bar (1.5 oz): 31 mg
Hershey’s Milk Chocolate, 1 bar (1.5 oz): 10 mg
Excedrin headache tablet, 1: 65 mg
caffeine tablet, 1: 200 mgPrecautions
People vary in their sensitivity to caffeine based on
their weight, age, medications they may be taking, and
personal biology. Individuals should be alert to how
much caffeine they consume during a day and how it
makes them feel, then moderate their intake accord-
ingly. Caffeine does not replace the need for sleep. All
mental and physical benefits are temporary and a
‘‘crash’’ is likely to occur after a dose of caffeine
wears off. People who use caffeine to stay awake to
drive or operate heavy machinery are at risk of being
involved in an accident because of excessive tiredness
once the effect of caffeine wears off.
Caffeine stays in the system of pregnant women and
people with liver damage longer than normal. These
people should closely monitor their caffeine intake.
Caffeine passes into breast milk and although it
may have no effect on thebreastfeedingwoman, it
may make the infant restless, irritable, and less likely
to sleep.
Athletes should be aware that the International
Olympic Committee tests for caffeine levels over 12
mg/ml of urine. This level could be reached by drink-
ing four large cups of coffee.Interactions
Caffeine appears to enhance the effectiveness of
over-the-counter headache remedies. Some of these
medications contain a mixture of caffeine and pain-
killer. People with a high sensitivity to caffeine should
read the labels carefully.
People taking diuretic medication (waterpills)
may see increased urine output because caffeine is a
weak diuretic.Complications
Although caffeine in moderate amounts poses no
major health risks, the body quickly develops toleranceCaffeine