Caffeine is a stimulant
compound belonging to the xanthine class of chemicals naturally found in coffee,
tea, and (to a lesser degree) cocoa or chocolate. It is included in many soft
drinks, as well as a larger amount in energy drinks. Caffeine is the world's
most widely used psychoactive drug and by far the most common stimulant. In
humans, caffeine acts as a central nervous system stimulant, temporarily warding
off drowsiness and restoring alertness. but unlike many other psychoactive
substances, it is legal and unregulated in nearly all parts of the world. 90% of
adults consume caffeine daily
In 1821 relatively pure caffeine was isolated for the first time by the German
chemist Friedlieb Ferdinand Runge. According to legend, he did this at the
instigation of Johann Wolfgang von Goethe (Weinberg and Bealer 2001). He called
this substance kafein, which means "something found in coffee." Caffeine was not
synthesized until 61 years later in 1882, by the German chemist and Nobel
laureate Emil Fischer.
Purified caffeine powder can be synthesized from a variety of starting
materials, such as urea, xanthine, theophylline, and theobromine. The high
demand for decaffeinated products has resulted in an abundant supply of caffeine
washes extracted from coffee and tea. The relative ease of purification of
caffeine from these decaffeination liquids makes synthesis much more expensive
by comparison. Today, most caffeine powder is derived from these natural
extracts
Caffeine extraction is an important industrial process and can be performed
using a number of different solvents. Benzene, chloroform, trichloroethylene,
and dichloromethane have all been used over the years, but for reasons of
safety, environmental impact, cost and flavor, they have been superseded by two
main methods: water and carbon dioxide.
In the water method, green coffee beans are soaked in water. The water extract,
which contains not only caffeine but also many flavor compounds, is then passed
through activated charcoal, which removes the caffeine. The water can then be
put back with the beans and evaporated dry, leaving decaffeinated coffee with a
good flavor. Coffee manufacturers recover the caffeine and resell it for use in
soft drinks and medicines.
Part of the reason caffeine is classified by the Food and Drug Administration as
generally recognized as safe is that toxic doses (over 1 gram for an average
adult) are much higher than typically used doses (less than 500 milligrams).
Ordinary consumption has low health risks, even when carried on for years –
there may be a modest protective effect against some diseases, including
Parkinson's disease, heart disease, and certain types of cancer. Some people
experience sleep disruption if they consume caffeine, especially during the
evening hours, but others show little disturbance and the effect of caffeine on
sleep is highly variable. Caffeine has a number of effects on sleep, but does
not affect all people in the same way. It improves performance during sleep
deprivation but may lead to subsequent insomnia. In shift workers it leads to
fewer mistakes caused by tiredness. In athletics, moderate doses of caffeine can
improve sprint, endurance, and team sports performance, but the improvements
are usually not very large. Some evidence suggests that coffee does not produce
the ergogenic effects observed in other caffeine sources. High doses of
caffeine, however, can impair athletic performance by interfering with
coordination.There is also evidence that caffeine may be helpful at high
altitude.
Consumption of 1000–1500 mg per day is associated with a condition known as
caffeinism Caffeinism usually combines caffeine dependency with a wide range of
unpleasant physical and mental conditions including nervousness, irritability,
restlessness, insomnia, headaches, and heart palpitations after caffeine use.
Coffee consumption is associated with a lower overall risk of cancer This is
primarily due to a decrease in the risks of hepatocellular and endometrial
cancer, but it may also have a modest effect on colorectal cancer.There does not
appear to be a significant protective effect against other types of cancers, and
heavy coffee consumption may increase the risk of bladder cancer. Moderate
coffee consumption may decrease the risk of cardiovascular disease, and it may
somewhat reduce the risk of type 2 diabetes.Drinking four or more cups of coffee
per day does not affect the risk of hypertension compared to drinking little or
no coffee. However those who drink 1–3 cups per day may be at a slightly
increased risk. Caffeine increases intraocular pressure in those with glaucoma
but does not appear to affect normal individuals. It may protect people from
liver cirrhosis.There is no evidence that coffee stunts a child's growth.
Caffeine may increase the effectiveness of some medications including ones used
to treat headaches. Similarly, intravenous caffeine is often used in hospitals
to provide temporary pain relief for headaches caused by low cerebrospinal fluid
pressure.
Some studies suggest that caffeine intake may increase calcium loss in the
urine. However, any loss has been found to be minimal and caffeine intake at
normal levels does not appear to affect calcium balance or bone density. More
recent studies have confirmed that caffeine intake is not a risk factor for
osteoporosis, particularly in women who consume adequate calcium.
A large number of studies have looked at the effects of caffeine-containing
beverages on reproductive factors. The data suggests that moderate caffeine
consumption is safe for a pregnant woman and her unborn child. Results from
studies into caffeine intake and time taken to conceive have provided no solid
evidence that consumption of caffeine containing beverages may reduce the
likelihood of a woman conceiving. Two major studies in the U.S. found no
correlation between caffeine consumption and pregnancy outcome or birth defects.
In addition, recent studies have found no correlation between caffeine intake
and spontaneous abortion or abnormal foetal growth. However, questions remain
about the effects of high doses of caffeine and it is wise for pregnant women to
practice moderation (300mg per day or 3-4 cups of instant coffee).
Children generally have the same ability to process caffeine as adults. Studies
have shown that foods and drinks containing caffeine when taken in moderate
amounts have no detectable effects on hyperactivity or attention span of
children. However, in sensitive children, high doses of caffeine, may cause
temporary effects such as excitability, irritability or anxiety.
Caffeine is well recognised as increasing both alertness levels and attention
spans. A cup of coffee or tea is often recommended to counter sleepiness,
especially for those driving long distances and many people resort to an
afternoon "cuppa" to get back on top of their workload. Studies have shown that
caffeine may also improve memory and logical reasoning. Many caffeine-containing
beverages, most notably tea and more recently coffee and chocolate, have been
found to contain antioxidants. Antioxidants appear to have health benefits
especially in the area of heart health and cancer prevention. Recent reports
suggest that caffeine may be useful in treating allergic reactions due to its
ability to reduce the concentration of histamines, the substances that cause the
body to respond to an allergy-causing substance. More research is need in this
area before conclusions can be drawn however. Caffeine has long been known to
help some people suffering from asthma
Caffeine is sometimes administered in combination with analgesics to increase
their effectiveness, such as with ergotamine in the treatment of migraine and
cluster headaches, or with certain pain relievers such as aspirin and
acetaminophen. Caffeine may also be used to overcome the drowsiness caused by
antihistamines. Cessation of breathing (apnea) in premature infants is sometimes
treated with citrated caffeine, which is available only by prescription in many
countries.
When taken in excess, caffeine use has been correlated to nervousness, insomnia,
jitteriness, and reduced depth of sleep (Hoeger, Turner and Hafen 2002). Long
term effects of prolonged repeated use can include risk of stomach ulcers,
dependence, and withdrawal symptoms (headache, irritability, tiredness) (Hoeger,
Turner, and Hafen 2002). While relatively safe for adult humans, caffeine is
considerably more toxic to some other animals such as dogs, horses and parrots
due to a much poorer ability to metabolize this compound. Caffeine has a much
more significant effect on spiders, for example, than most other drugs do (Noever,
et al. 1995)
Caffeine's toxicity to humans There has been extensive research on caffeine and
this drug’s effect on the health of human beings. The Food and Drug
Administration (FDA) concluded in 1958 that caffeine is recognized as safe for
consumption. A recent review claims to have found no signs or evidence that
caffeine’s use in carbonated beverages would produce unhealthy effects on the
consumer.
American Medical Association (AMA) views caffeine as being safe for consumption.
They state that those drinking moderate amounts of coffee and tea probably do
not need to have concern for their health in regards to caffeine consumption (IFIC
2998).
The minimum amount of caffeine needed to cause death to human beings is
estimated to be 150-200 mg/kg of body weight. Symptoms of acute toxicity,
including nausea, vomiting, diarrhea, cramps, and possibly seizures (Sauer 1994)
may be observed after taking sublethal doses of caffeine. There have been some
deaths from intentional overdosing on caffeine pills.
Too much caffeine, especially over an extended period of time, can lead to a
number of physical and mental conditions. "The four caffeine-induced psychiatric
disorders include caffeine intoxication, caffeine-induced anxiety disorder,
caffeine-induced sleep disorder, and caffeine-related disorder not otherwise
specified (NOS)."
Caffeine-induced psychosis, whether it be delirium, manic depression,
schizophrenia, or merely an anxiety syndrome, in most cases will be hard to
differentiate from other organic or non-organic psychoses....The treatment for
caffeine-induced psychosis is to withhold further caffeine." One study declared
that "although infrequently diagnosed, caffeinism is thought to afflict as many
as one person in ten of the population" (James and Stirling 1983).
Caffeine increases the production of stomach acid and tends to relax the
gastro-esophageal sphincter (Drug Facts and Comparisons 2001), which controls
the passage of materials between the stomach and esophagus. High intake of
caffeine over time can lead to peptic ulcers, erosive esophagitis, and
gastroesophageal reflux disease (GERD).
It is suggested that "slow metabolizers" who carry a variant of the enzyme
cytochrome P450 1A2 (CYP1A2) have an increased risk of nonfatal myocardial
infarction.
Caffeine metabolism
Caffeine is easily absorbed when taken orally, with 99 percent absorption
occurring within 15-120 minutes. A dose of 250 mg produces a peak plasma level
of 5-25 micrograms per milliliter (ml). In order for caffeine to be effective,
it must reach a plasma level of 6-13 micrograms/ml (Drug Facts and Comparisons
2001). After ingestion, caffeine has a physiological half-life in adults of
three to seven hours, with much longer values in neonates and pregnant women (PharmGKB
2004). It is rapidly distributed to all body compartments and crosses the
placenta and blood-brain barrier. Small amounts will also enter breast milk.
Continued consumption of caffeine can lead to drug tolerance. Upon withdrawal,
the body becomes oversensitive to adenosine, causing the blood pressure to drop
dramatically, which leads to headaches and other symptoms. Caffeine is
metabolized in the liver, through demethylation and oxidation, by a cytochrome
P450 enzyme system known as 1A2 or CYP1A2. In the first stage it forms three
dimethylxanthines:
* 1,7-dimethylxanthine (paraxanthine) at 80-84 percent
* 3,7-dimethylxanthine (theobromine)at 10-12 percent
* 1,3-dimethylxanthine (theophylline)at 4 percent
Each of these metabolites is further metabolized and then excreted in the urine,
primarily as methylated urates and methylated xanthines. About one percent of
caffeine enters the urine unchanged.