Stimulant Beverages
There are only a few commonly consumed beverages that
have a stimulant effect. They are: coffee, tea, chocolate and
certain soft drinks like Coca Cola. What do they have in
common that makes them stimulants?
Caffeine (and other alkaloids that differ among plants) – all
are stimulants to the mammalian CNS. They are collectively
called secondary chemicals. This means plants produce them
as offshoots/slight modifications to normal metabolism.
The most likely function for these chemicals is to act against
herbivores.
Caffeine is rapidly absorbed from the stomach and small
intestine (within 45 minutes of ingestion), and distributed
throughout the body by the circulatory system. It has effects
on many systems…
In the liver it is metabolized by the same enzyme system that
works on organic pollutants, the P450 system. There are
three metabolites produced by that metabolism:
1. Paraxanthine – increases glycerol and fatty acid levels in
circulation
2. Theophylline – relaxes smooth muscles, particularly in the
bronchi. In higher doses than you can get from beverages it
can be used as an asthma treatment.
3. Theobromine – same stuff as in chocolate. Dilates blood
vessels and acts as a weak diuretic.
Caffeine also crosses the blood-brain barrier, and its structural
similarity to adenosine seems to cause a number of other
effects.
Those effects include:
Blocking adenosine receptors, which in turn results in
increased activity of dopamine. This is the root cause of the
stimulating effect.
Increases in serotonin levels that ‘improve’ mood.
An increase in epinephrine, the adrenal hormone involved in
flight-or-fight responses. It stimulates the sympathetic nervous
system, resulting in increased heart rate, blood pressure, and
blood flow to the muscles.
It blocks cyclic nucleotide phosphodiesterase, resulting in
increased levels of cyclic AMP. That prolongs the effects of
epinephrine.
Caffeine is believed to lower the chances of getting
Parkinson’s disease (in men; in women the result is uncertain),
and may also lower the probability of becoming type II
diabetic.
Caffeine is a sufficient stimulant of physical performance (7%
increase in work output, 19% increase in exercise endurance)
that the IOC has set a urinary output threshold. The IOC limit
is 12 g/ml urine; that would be the result of consuming 8
cups of coffee in 2-3 hours. The U.S. NCAA has set its limit at
15 g/ml urine.
All that sounds relatively positive. However, there are also
negative effects:
One can habituate to caffeine, but in occasional consumers (23 cups of coffee per day) consumption of >250 mg typically
results in headaches, nervousness, irritability, anxiety, and
even muscle twitching. There are even names for these
‘diseases’ – caffeinism when the caffeine comes from coffee
drinking, theism when the source of caffeine is tea.
Habitual users have the opposite problem – withdrawal
symptoms. Abstinence for more than a day results in
headache, irritability, insomnia, and dysphoria (the opposite of
euphoria).
Long-term overconsumption (~15 cups of coffee or more per
day) can have serious consequences, including heart attack.
Other negatives:
Caffeine consumption is associated with birth defects and with
infertility in women.
Caffeine can exacerbate heart problems through causing
increased level and persistence of epinephrine and vasoconstriction raising blood pressure. (Note the opposite effects
of some caffeine metabolites with respect to smooth muscle
and blood pressure!)
Caffeine is addictive, with more rapid recovery from
withdrawal symptoms than with drug addiction, but many of
the same problems during withdrawal.
How much caffeine do we get from some of our favorite
beverages?
Beverage
Caffeine per serving (mg)
Brewed coffee
135
Excedrin tablet
65
Expresso coffee
100
Chocolate (dark, 1.5oz bar)
31
Red Bull
80
Jolt Cola
150
Mountain Dew
54.5
Coca Cola
34
Tea (leaf or bag)
50
Now, what are the plants, the sources and current production
of coffee and tea?
Coffee
Coffee is made by roasting, grinding, and brewing the seeds
of Coffea arabica (Rubiaceae) mostly. The drink and use of
the seeds can be traced back to the Ethiopian highlands in the
9th century. There are other species of Coffea, but only one,
with more caffeine but inferior flavor, is grown commercially
– C. robusta.
Originally the coffee berries (beans) were eaten raw and
whole. Later they were crushed with fat and eaten as a ‘food’.
Coffee was spread from Ethiopia into the Middle East by the
13th century. By then coffee beans were roasted much like
today.
By 1500 coffee was widely cultivated in Yemen, and had been
carried to southern Asia (particularly Sri Lanka and Java). It
became an important social drink in coffeehouses. The muslim
Imams did not approve of coffeehouses, but their popularity
prevented forcing closure. The name mocha comes from the
Yemeni port from which beans were exported. The name java
similarly arises from an early important source of beans.
Coffee was imported to Europe by traders in 1615. By 1700
there were coffeehouses spread over Europe. They were, much
like in the 1960s, centers of art, culture, political debate and
discussion; Lloyd’s of London began from insurance
underwriters meeting in a dockside coffeehouse.
There were coffee plantations in South America by 1720, and
a North American coffeehouse in Boston (using beans
imported from Europe) in 1669. Coffee was initially not as
popular in North America as in Europe. However, as the
British reduced access to and taxed tea (resulting in the Boston
‘tea party’), coffee consumption grew.
Today both species of coffee are grown. Cheaper C. robusta
beans caused a major global economic dislocation. C. robusta
trees (really evergreen bushes) are more tolerant of (and
actually ‘like’) bright light conditions, and can be grown in
open plantations where machine harvesting is possible. It is
more disease-resistant.
Less efficient hand harvesting and tree/bush management of
shade-grown C. arabica led to small coffee growers
abandoning their plantations; world price did not meet cost of
production for them. Now you can find “Fair Trade” coffee.
Growth also requires year round rain, total precipitation of 1 –
1.5 m, and a temperature not varying much from ~20°C.
C. arabica accounts for about 75% of the world’s commercial
coffee crop.
The leading producers (2007) are:
Brazil
17 million metric tons (C. arabica +)
Vietnam
15.6
“
(C. robusta)
Columbia
9.4
“
(C. arabica)
Indonesia
2.8
“
(C. arabica +)
r:Coffea canephora
m:Coffea canephora and Coffea arabica
a:Coffea arabica
Structure of coffee berry
and beans: 1: center cut
2:bean (endosperm) 3:
silver skin (testa,
epidermis), 4: parchment
(hull, endocarp) 5: pectin
layer 6: pulp (mesocarp)
7: outer skin (pericarp,
exocarp)
The red berry is the fruit. Each fruit contains two seeds (beans)
with their ‘flat’ sides oriented towards each other. It takes
about 7 years for a coffee tree to mature and produce fruit.
Growth is optimum between 1,300 and 1,500 m altitude, but
some coffee is grown from sea level to 2,800 m.
Since the flavor of coffee is very dependent on harvest at exact
ripeness, most high quality (arabica) coffee is still picked by
hand.
Coffee production in some places (Sri Lanka, Indonesia,
Africa) has been limited by a fungal rust (Hemileia vastatrix).
C. robusta is resistant. Sri Lanka was so affected that it shifted
from coffee to tea production. Production of arabica beans is
limited to areas that have never been infested with the rust.
Harvested beans are first de-pulped to extract the beans.
In the Americas this is done by the ‘wet method’. Fruits are
floated in tanks to remove other debris, then mechanically depulped. Pulp remaining is allowed to ferment for a day. Beans
are washed and dried, and seed coats are mechanically
removed. Beans are then roasted.
In the dry method used in Africa, fruits are spread in the open
and allowed to dry for days. The pulp ferments, then the pulp
is removed mechanically, and the beans can be roasted.
Roasting
The roasting process produces the flavor and aroma of coffee.
The end points of roasting are: light roasts (beans look pale to
chocolate brown) at 212-218°C producing a milder coffee with
more caffeine – to dark roasts (French black and expresso,
beans come out black) at 240 -250°C producing stronger and
typically more bitter coffee.
Expresso roast
Roasting turns starches into sugars in the beans, then, at the
final roasting temperature carmelizes the sugars. At just below
240°C sugars are burned to carbon. Thus lighter roasts only
carmelize the sugars, while expresso roasts carbonize them.
The oils that give coffee aroma are also driven out of cells to
the surface of the beans by roasting.
Unroasted beans can be stored for extended periods without
detriment. Roasted beans only have a shelf life of somewhat
more than one month. That’s the reason quality coffee beans
are vacuum packed. However, roasted beans cannot be
immediately vacuum packed; they emit CO2 for a few days
after roasting, and packing has to be delayed.
Ground coffee has a shelf life of no more than a few days.
Grind it just before brewing if you can.
Refrigerate (or even freeze) ground coffee to retain as much
of the flavor as possible.
Processed coffees
Instant coffee was developed in 1901 by Satori Kato, a
Japanese chemist working in Chicago. During WW I the U.S.
found the light shipping weight and rapid preparation a great
advantage, and shipped it to the troops.
However, it was not an instant hit. Nescafé finally launched
commercial instant coffee in 1938.
Production: usually lower quality, cheaper beans are used.
After roasting and grinding, coffee is ‘brewed’ by percolation
through columns at >300°F. This coffee is concentrated (15 –
30% coffee solids). It is then dried to crystals by either
spraying (spray drying, evaporating the water) or freeze
drying (wet coffee is frozen, then placed in a vacuum
chamber; water ‘evaporates’, leaving coffee crystals).
This is one granule of freeze dried coffee. The large pits are
what remains of air bubbles, left when the air is removed in
vacuum.
Decaffeination
Caffeine is removed from unroasted, green coffee beans. The
first version of the process was developed by German
chemists Ludwig Roselius and Karl Wimmer in 1903. Beans
were steamed in salt water brine, then caffeine was extracted
using benzene as the solvent. Decaffeinated coffee made this
way was sold as Sanka brand.
Benzene is now recognized as a carcinogen. It is no longer
used as the solvent. Now methylene chloride (banned in
hairspray as a carcinogen) and ethyl acetate are used. After
steaming, beans are soaked in these solvents for 10 hours,
then steamed again for 10 hours to remove any residual
solvent.
An alternative is Swiss water decaffeination. Beans are soaked
in hot water until all the coffee flavors and caffeine are
released. Beans are discarded, and the water and coffee solids
pass through carbon filters that absorb the caffeine. This water
is then used to extract caffeine from beans without losing
flavor. The soaking in ‘flavor-charged’ water can be repeated
until >99% of caffeine has been removed.
However [from Dr. Crosby] a comedian/musician named Bob
Irwin apparently said drinking decaffeinated coffee is “like
kissing your sister/brother”. Make your own decisions about
caffeine…
Tea
Tea is a beverage brewed by steeping processed leaves, twigs,
and/or buds of plants. What we usually mean by tea is brewed
using leaves of Camellia sinensis [Theasceae].
The various types of tea are determined by how the leaves are
processed. After the leaves are picked they begin to wilt and
oxidize. The leaves darken because chlorophyll breaks down
and tannins are released. The tea industry calls this
fermentation, though it is not biological fermentation (no
microbes involved). The process is stopped at different stages
to produce the varieties of tea.
1. White tea – produced from young buds with oxidation
prevented. Buds are shielded from sunlight to prevent
chlorophyll formation.
2. Green tea – oxidation is stopped very early, either with
steam (Japanese method) or dry cooking in pans (Chinese
method).
3. Oolong tea – oxidation is allowed to continue for 2 – 3
days. The process is then stopped and the leaves further
processed.
4. Black (or red) tea – the oxidation process is allowed to
continue for 2 weeks to one month. The leaves turn black,
but the liquid tea is reddish.
5. Kukicha (or winter) tea – made from twigs and old leaves
pruned during the dormant season and dry roasted over fire.
The small tips of oolong tea leaves are what make up ‘Orange
Pekoe’ tea.
Jasmine tea is made by adding dried Jasmine flowers to the
tea.
Earl Grey tea has been infused with bergamot oil.
Herbal teas generally have no tea leaves. Instead they have
various plant parts replacing tea leaves, e.g. rose hip or
chamomile.
Tea bags are made with the broken leaves of the various
varieties of tea.
About 3% of the dry weight of tea is caffeine. Tea also
contains catechins (antioxidants, up to 30% of dry weight),
with a much larger content in white and green teas than in
oolong or black tea. It also has both theobromine and
theophylline.
The cradle of the tea plant is a region that encompasses eastern
and southern China, northern Myanmar, and Assam in
northeastern India. The variant sinensis grows naturally in
eastern and southeastern regions of China.
China is the first place where tea drinking was recorded,
dating back to 2737 BC, when a tea leaf accidentally fell into
water being boiled for drinking.
Green tea was drunk in Japan at least as early as 900 AD.
Tea reached Europe in the second half of the 16th century.
Tea had become popular in the American colonies by the mid1700s. In the colonies much more tea was consumed than
coffee. The British passes the Tea Act in 1773. It was not a
new tax on tea, rather it was an act to allow the British East
India Company to avoid a colonial tax on tea, and therefore
undercut colonial merchants who had to pay the tax.
That led to the Boston Tea Party, when the Sons of Liberty,
dressed as Native Americans, dumped 342 crates of British
East India tea into Boston Harbor. The tide was out, and many
of the crates actually stood out above the water. Retaliatory
measures the British took led to the American Rebellion.
Camellia sinensis is an evergreen plant and grows in tropical
to sub-tropical climates. In addition to tropical climates (at
least 50 inches [slightly less than 1½ m] of rainfall a year), it
also prefers acidic soils. Many high quality tea plants grow at
elevations up to 5,000 feet (1524 meters), as the plants grow
more slowly and acquire a better flavor. Only the top 1-2
inches (tip leaves) of the mature plant are picked.
Tea production
China
India
Kenya
Sri Lanka
Turkey
Global total
800,000 tons
820,000 tons
328,000 tons
309,000 tons
205,500 tons
3.2 million tons
Health effects of tea
The catechins in green and white tea may have antibiotic
effects, resulting from disrupting bacterial DNA replication.
Green tea has been reported to reduce growth rate of breast
cancer (controversially, the FDA says the evidence is
insufficient). The only experimentally documented effect on
cancer derives from the presence of a catechin
(epigallocatechin gallate) that affects a lung cancer cell
binding site and evidence that the same binding protein may
be important in prion disease (Creuzfelt-Jacob/mad cow).
Green tea may improve insulin sensitivity (of value in treating
type II diabetes), and may even help prevent the occurrence of
diabetes.
Theanine (from tea leaves) seems to boost immune response
when fighting a disease – coffee does not have this effect.
Immediately after stress the stress hormone cortisol declines
back to near normal levels more rapidly in regular drinkers of
black tea (no info about other types of tea). These same
subjects had lower levels of blood platelet activation, which
should reduce the probability of cardiac thrombosis.
Drinking 3 cups or more of tea per day is apparently
associated with decreased risk of stroke and cardiovascular
disease.
There are some negatives: remember that tea contains
caffeine. Drinking enough tea to gain some of those benefits
may also expose you to risks of excess caffeine consumption.
Tea leaves contain oxalates. If you drink a lot of tea, the
oxalates (in low amounts in general) can bind calcium and can
cause kidney stones.
Kola drinks
The seeds of the Kola tree (Cola nitida) are the basic flavor
source. The tree is native to West Africa (Sierra Leone and
around the Niger delta), and related to the cacao tree. It is now
cultivated in the West Indies, Brazil and Java, as well.
The cola nut is the source of caffeine in these beverages.
A little history: Coca Cola was invented by John S. Pemberton
in Atlanta in 1885. Originally it was a ‘cocawine’, but reformulated into coca cola at the outset of prohibition. The first
recipes used fresh coca leaves, and contained 9 mg of cocaine
per glass. Later, the recipe called for “spent leaves” from
which the cocaine had already been extracted.
Other ingredients: Kola seed extract, caramel, high fructose
corn syrup, vanilla, cinnamon, lime juice and orange oil.
The U.S. Federal government allows one ‘farm’ in New Jersey
to grow Coca plants for production of Coca Cola.
There have been a number of legal and political ‘shenanigans’
associated with who owns and controls coke’s formula. Asa
Griggs Candler, who founded what is now Coca Cola,
apparently forged at least two signatures to take control of the
formula – the inventor Pemberton’s and Margaret Dozier.
The original recipe is held in the Sun Trust bank vault in
Atlanta, and is a closely guarded industrial secret. It’s held
there because Sun Trust’s predecessor was the underwriter for
Coca Cola’s initial public stock offering. Myth (??) has it that
only two executives have access, and each to only half the
formula.