Caffeine
(Ch. 13)
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THE HISTORY OF
COFFEE IS LONG; COFFEE DRINKING HAS GONE THROUGH PERIODS OF BEING CONSIDERED
BOTH GOOD AND BAD
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On a daily basis,
more people use caffeine than any other psychoactive drug
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Caffeine belongs
to the Xanthines class of chemicals. The Xanthines include; caffeine, theophylline
and theobromine. They are methylated xanthines - very similar in structure
and closely related to alkaloids.
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Legend has it that
Arabian goatherd Kaldi is the figure who first discovered caffeine
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An Arabian medical
book in 900 AD listed its beneficial uses
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Coffeehouses appeared
by mid-17th century (1650) and were places to gather to talk
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Americans were tea
drinkers until they boycotted tea because of the British Tax Act in 1765.
Coffee became the new country's national drink
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The Middle East
discovered that roasting green coffee beans improved the flavor, aroma
and color
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Commercial roasting
started in 1790 in NYC and the process gradually spread through the country
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In 1946 the annual
per capita coffee consumption reached an all-time high of 20 pounds. The
overall trend has been basically downhill since then, in spite of all the
interest in expresso and specialty coffees.
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In the early 1950s,
about 94% of American coffee came from Latin America - since then there
has been a steady decline. Today less than half of the is grown in this
hemisphere. Brazil is the principle exporter to the US, with Columbia second.
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Both countries grow
arabica,
which has a caffeine content of about 1%; and robusta, with a caffeine
content of about 2%, is the variety grown in Africa and is usually of a
lower grade and price
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The economics of
coffee (its number two in international trade, behind oil) have as much
to do with coffee consumption as does our changing lifestyle. Two things
happen when prices go up: the quality of coffee decreases and people drink
less coffee.
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In the 1980s, Americans
began to drink more decaffeinated coffee and less regular coffee - to remove
caffeine, unroasted beans are soaked in an organic solvent (usually methlene
chloride), then roasted. The FDA placed limits on its residue (not to exceed
ten parts per million)
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TEA IN THE UNITED
STATES
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Tea comes from the
tree, Camellia sinensis
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The first report
of the use of tea is 360 A.D.Medically, there were claims tea cured many
ills, but claims were also made that it caused harm
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In 1600 the English
East India Company was formed, and Queen Elizabeth gave the company a monopoly
on everything from the east coast of Africa across the Pacific to the west
coast of South America. Through the Stamp Act of 1766, enacted by Parliament,
a tax was placed on tea. This made the colonists unhappy and they boycotted
consumption of English tea. By now, the East India Company was in serere
financial trouble and to aid the company, Parliament gave the company the
right to sell tea in the American colonies without paying the tea tax and
to sell the tea through its own agents, eliminating profits to the merchants
in the colonies. These activities resulted in the Boston Tea Party of December
16, 1773 and the Revolutionary War.
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Today, most of the
tea (~70%) that comes to America comes from the mountains of Sri Lanka,
India or Indonesia. Pluckers select only the bud-leaf and the first two
leaves at each new growth. The bud-leaf is called the flowering orange
pekoe (refering to the size and quality of the tea leaf), and the second
leaf is larger and called orange pekoe an the third and largest leaf is
called pekoe.
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Leaves are dried,
rolled to crush the cells in the leaf and placed in a cool damp place for
oxidation to occur - this turns the green leaves to a bright copper color
(and now referred to as black tea - 98% of the tea that Americans consume).
Nonoxidized leaves are packaged and sold as green tea
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In 1902 iced tea
was sold for the very first time at the Louisiana Purchase Exposition in
St. Louis and tea was placed in bags for brewing.
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The largest seller
of tea in America is the Lipton Tea Company
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Tea also contains
theophylline
which is very effective at relaxing the bronchial passages
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CAFFEINE IS INCLUDED
IN MANY FORMS OF FOOD OR DRINK
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Chocolate is made
from the Theobroma cacao bush. It contains caffeine, but its active
ingredient is theobromine - a xanthine that has physiological actions
that closely parallel those of caffeine but are less potent in its effects
on the CNS. The average cup of cocoa contains about 200 mg of theobrimine
but only 4 mg of caffeine
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In 1847 the first
chocolate bars appeared; and in 1876 milk chocolate was invented and sold
by the Nestle company. By FDA standards, milk chocolate must contain at
least 12% milk solids
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Many soft drinks
contain large amounts of caffeine. Today soft drinks cannot contain more
than 0.02% of caffeine (~0.2 mg/ml; or 6 mg/oz.). Soft drinks with high
caffeine content are very popular among children and teenagers causing
concern about the potential for behavioral disturbance and for dependency.
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Caffeine is common
in several over-the-counter drugs
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CAFFEINE CAUSES
SEVERAL PHYSIOLOGICAL AND BEHAVIORAL EFFECTS
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The three xanthines
have similar effects on the body, but caffeine has the graetest effect.
Theobromine has almost no stimulant effect on the CNS and skeletal muscle.
Theophylline is the most potent, and caffeine the least potent agent on
the cardiovascular system. Caffeine has been the most extensively studied.
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It causes dependence
and tolerance, although tolerance is generally low grade. The reinforcing
effect of caffeine contributes to the psychological dependence. There is
also physical dependence as well.
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caffeine and the
other xanthines block the brain's receptors for adenosine, a neurotransmitter.
Adenosine normally acts in several areas of the brain to produce behavioral
sedation by inhibiting the release of other neurotransmitters. Caffeine's
stimulant action results from blocking the receptors for this inhibitory
effect.
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Physiological effects
include CNS and respiratory stimulation as well as dilation of the bronchial
tubes. There is a strong relationship between the mood-elevating effect
of caffeine and the extent to which it will keep an individual awake. Higher
dose levels (500 mg) are needed to affect the autonomic centers of the
brain, and heart rate and respiration can increase at this dose.
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Caffeine acts directly
on the vascular muscles to cause dilation, wheras stimulation of the autonomic
centers results in constriction of blood vessels.
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Behavioral effects
are somewhat inconclusive at this time although caffeine does seem to produce
an anxiety-like reaction
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THE USE OF CAFFEINE
HAS LED TO SOME COCERN IN THE MEDICAL PROFESSION
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It is important
to point out that there is not yet clear evidence that moderate caffeine
consumption is dangerous, the scientific literature has investigated the
possible effects of caffeine in cancer, benign breast disease, reproduction
and heart disease. The problem in knowing for certain about some of these
things is that epidemiological research on caffeine consumption is difficult
to do well. Coffee drinkers tend to do "other" things - smoke, work at
jobs that require long hours without sleep, etc. - is it the activity that
produces the effect, or is it caffeine?
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Although suspected,
no link has been found between coffee consumption and pancreatic cancer
or fibrocystic breast disease
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Caffeine may be
linked to difficulty in becoming pregnant, to miscarriages, and to slowed
fetal development
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Drinking 5 or more
cups of coffee daily can increase the risk of heart disease - based upon
increase heart rate, increased blood pressure and the increase in blood
cholesterol levels.