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Tea and Caffeine |
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What is This Caffeine Doing in my Teacup?
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"Thank you! It is a pleasure to speak to you today. I stand before you with a story to tell and a confession
to make. The story is about caffeine from the Camellia sinensis (Cs) tea plant to you and me. The
confession is that I am a bicaffual. Don't try to look that one up in the dictionary. It's not there. As
a bicaffual, I enjoy the caffeine in both coffee and tea. I don't stand before you as an expert on caffeine
but someone who, like many of you, feels the need for caffeine to get through the day. Let be give you an example.
My human pathology class meets at eight o'clock in the morning. Although I've taught this class for many
years, each morning I would still wake up thinking, I can't do this. "My mind is mud and how am I going to
present lucent information in this condition? In less than two hours I would be standing in front of over
100 bright, health professional students. I begin to feel stressed. I exit my shower still feeling my mind
is a large clot. I prepare myself a large cup of green tea. I drink it but still feel that all of the
information I need for the lecture is bottled up in my brain. After a little breakfast, I get on my bicycle
and ride toward my favorite coffee shop in the cold mountain air. I arrive at the coffee shop, order my
triple espresso and proceed to the window where there is plenty of light. I consume half of my espresso and
open my lecture notes only to stare at them. I feel my anxiety rising when I tell myself that I have only 30
minutes to pull all of this together. In my anxiety, I gulp down the remainder of my espresso.
But then, like a clogged drain opening, something in my mind would open. It was like a lazy creek suddenly
receiving a burst of rain from higher in the mountains. The mud in my brain was rapidly being converted into
some energetic liquid. Yes, I said to my self, I can do it. Only then, would I get on my bike, full of thoughts,
eager to present complex information about cancer, heart disease or diabetes to my students. What did the caffeine
do to my brain? I want to explore answers to this and several other questions:
Why Does the Cs Plant Synthesize Caffeine?
Typically, 4-5% of the dry weight of the Cs bud is consists of caffeine. The first two leaves are likely to
contain 3-4% caffeine when dried. The further down the growing branch the less caffeine we find. Approximately
1-3% of the dry weight of the third through fifth leaves is due to caffeine. Dividing Cs cells produce caffeine
and the closer to the tip of the branch, the faster the cells divide. Therefore, the largest amount of caffeine
is present in the exact parts of the plant we select for making green tea. Why does the Cs plant synthesize caffeine?
For protection! The Cs plant synthesizes caffeine in order to protect itself against other plants, from insects,
microbes and other threatening life forms. For example, you and I look at the "two leaves and bud" parts of the
tea plant as the most flavorful teas. But the insect looks at these parts as juicy morsels of food. The caffeine
is bitter and these parts don't taste good. Caffeine is also toxic. It is especially toxic to growing cells
of most species. For example, if caffeine gets into the soil from Cs plant parts falling to the ground, it deters
germination in other plants that would otherwise compete with it. Caffeine helps restrict the growth of competing
plants. Caffeine is synthesized by the growing Cs cells in order to protect themselves from other insects, competing
plants and other threatening life forms.
If Caffeine is Toxic Why Doesn't It Kill the Flushing Cs
Cells that Make It? Why not Us?
At concentrations of 1% or above caffeine is indeed toxic to most living cells. How is it that
caffeine does not kill the very cells that make it? Well it would if the caffeine were to come into contact with
the nucleus or even the cytoplasm of the cell. But the Cs cells don't let this happen. It is made in the cytoplasm
and quickly shuttled to and stored in the large drop like vacuole in the cell's interior. This vacuole is like a
small water bag surrounded by a vacuolar membrane. The vacuolar membrane serves as a wall between caffeine and other
storage products and the living parts of the cell. By living parts I mean the cytoplasm and the nucleus. If an
insect were to eat the cell, it would ingest a large amount of bitter-tasting caffeine but the vacuolar membrane
separates the caffeine from the living components of the growing Cs cells.
Why doesn't caffeine kill us when we drink a caffeinated beverage such as green tea?
Concentration! Caffeine is indeed toxic to us in large concentrations. Caffeine is especially toxic to
growing cells; it tends to stunt growth. Most physicians recommend that pregnant women restrict their intake
of caffeine for this reason. In large, really huge, amounts it can stunt human embryonic or fetal growth.
Caffeine, like most drugs, is called a drug when ingested in very small concentrations. Take
alcohol or aspirin for example. Ingest enough alcohol, aspirin or caffeine and it is toxic. Ingest much
smaller amounts as we normally do and caffeine serves as a drug. We will discuss later how caffeine works as
a drug, particular in concentrations ingested in common caffeinated beverages.
Why is caffeine not toxic to the dividing Cs cells that make it? For the same reason that an
ardent criminal is locked away in prison. Caffeine is, in a sense, locked away in the cell vacuole and kept away
from the living parts of the cell that it may harm. Why is it not toxic to us? Because it is hugely diluted,
and in a fraction of the concentration found in the living Cs cell. In these minute concentrations it acts like
a drug rather than a toxin.
How Does Caffeine Contribute to the Cup of Green Tea?
Caffeine contributes to the cup of green tea in at least two ways. One, caffeine
contributes a bitter flavor to tea. But, this is when it is not complexed with other compounds in tea. In a
properly-brewed cup of tea, the uncomplexed bitter caffeine taste adds a desirable dimension to the flavor profile
of tea. Two, it plays an important role in the larger, flavorful polyphenolic molecules of which it becomes a
part. The small caffeine molecule is an important building block in the larger molecules important for natural
green tea flavors. Interestingly, caffeine often complexes with catechin molecules. These, in turn, enter the
bloodstream as a caffeine-catechin complex rather than caffeine entering the bloodstream separately from catechin
molecules. In summary, the small amounts of caffeine in a cup of green tea are vital for the desirable flavors of green tea.
How Much Caffeine is in Green Tea Compared
to Other Caffeinated Beverages?
Here are some numbers related to the amounts of caffeine in popular caffeinated beverages such
as green tea. I have pulled together these numbers from a variety of sources. Here, I attempt to be consistent
in liquid volume amounts. There is no use to comparing the amounts of caffeine in an 8 oz. cup of coffee with a
5 oz. cup of green tea. I used 8 oz. rather than 5 oz. because a typical coffee/tea mug will contain about 8 oz
of tea or coffee. Factoring all of this in, I estimate that a typical cup of drip-brewed coffee is likely to
contain 135 mg. (milligrams) of caffeine; an 8 oz. well-poured, double espresso drink (e.g., latte) is likely to
contain 90 mg. caffeine; an 8 oz. cup of brewed black tea (e.g., English Breakfast), 85 mg.; oolong, 65 mg.; green,
40 mg.; cola soft drink, 23 mg. (or 34 in a 12 oz can); white tea, 18 mg.; standard sized milk chocolate bar, 10 mg.;
brewed decaffeinated coffee, 5 mg.; and brewed decaffeinated green tea; 2 mg. All of these figures are estimates but
they help put the caffeine amount in a cup of green tea into a larger perspective.
How Does Caffeine Enter the Human Body?
Caffeine is a highly water soluble compound. It begins to enter the bloodstream within
minutes of drinking a caffeinated beverage. Probably, most of the caffeine enters the bloodstream from
the stomach. Caffeine likely reaches its peak concentration in our bloodstreams about an hour or so
after drinking a cup of green tea. By the way, caffeine in green tea is more slowly absorbed than the
caffeine in coffee. In green tea brews, the caffeine molecules are more tightly complexed, connected, to
the polyphenols of the tea. In contrast, during the roasting process the caffeine molecules tend to separate
from polyphenols. The smaller, independent very water-soluble coffee caffeine molecules enter the bloodstream
faster than the larger complexes of green tea caffeine molecules. Those of us who drink coffee know that we
get our "caffeine hit" almost as soon as we consume the coffee. Whatever hit we get from green tea caffeine
is more gradual. Also, the theanine of green tea but not coffee also comes into play about the same time
as the caffeine. I, for example, am unaware of any caffeine hit when I drink green tea. On the other hand,
I look forward to the caffeine hit soon after my triple espresso. In addition, caffeine amounts are quite
different. I estimate my cup of green tea to contain about 40 mg. caffeine and my triple espresso to contain
about 135 mg. of caffeine.
How Much Time Does Caffeine Remain in the Human Body After Consuming It?
The body is somewhat friendly to caffeine. It tends to circulate in the bloodstream for several hours after
we consume it. The most common way we express caffeine's stay in the body is its half-life. By half-life, we
mean the amount of time that it takes for the body to metabolize or otherwise remove a substance from the body. The
half-life of caffeine varies in different individuals but is typically about 5 hours. For example, if 100 mg. of
caffeine is present in the bloodstream at 8:00 AM then there would be only 50 mg in the circulating blood five
hours later, at 1:00 PM. I also means that five hours after that, at 5:00 PM, there would be 25 mg. still in
the bloodstream. These numbers are gross approximations and vary with a lot of factors. For example, once the
first half-life time is reached the body appears to remove caffeine at faster rates. In the above example, perhaps
at 5:00 PM there may be no more than 15-20 mg of caffeine remaining in the circulating blood.
One reason for the accelerated rate of caffeine removal with time is that greater proportions of the body's caffeine
are in the circulating blood where it can be removed. Soon after we consume caffeine it is carried to all parts of
the body including the fluids associated with the brain. With increased time, more and more of this will exit the
brain and other parts of the body and return to the bloodstream where it is slowly removed.
How Does Caffeine Exit the Human Body?
The kidneys are able to slowly remove caffeine from the circulating blood. They leisurely take
out of the bloodstream and dump it into the urine. Most of the blood-borne caffeine is efficiently removed and
quickly altered as blood passes through the liver. This alteration process changes, metabolizes, the caffeine
molecule so that it is no longer a powerful brain excitatory agent. For example the liver alters the caffeine
molecule in a series of steps to theophyline, theobromine and other metabolites. These compounds may have
physiological activity if they are returned to the bloodstream. For example, theophylline is a bronchodilating
agent. That is, theophylline tends to expand the breathing passageways so that air passes into and out of the lungs
more easily. Theobromine, abundant in chocolate, also has physiological activity. When in the circulating blood
theobromine serves as a mild diuretic so that the kidneys release more urine. Theobromine also is a mild cardiac
stimulant and a systemic (throughout the body) vasodilator.
What About Caffeine and Chocolate When They Are Consumed Together?
I have been asked an interesting question regarding ingesting chocolate and caffeine together. Will
the large amounts of theobromine in the liver slow down the rate of caffeine conversion to theobromine. This would be
like shoveling caffeine to a higher and higher pile of theobromine slowing the caffeine transfer process. Theoretically,
this appears possible. If true, ingesting chocolate around the same time that caffeine is ingested may prolong the
half-life of caffeine in our bloodstreams.
In short, the liver metabolizes caffeine slowly to theophyline, theobromine and other metabolites
which are shifted and changed to eventually form uric acid. Uric acid, we recall, is a reasonably effective
antioxidant. Uric acid is also elevated in individuals who develop gout. We can see why many doctors don't want
their gout patients to drink caffeinated beverages. The kidneys efficiently remove uric acid the typical breakdown
product of caffeine. In this way, most of the caffeine we consume exits the body in the urine as uric acid.
Let's diverge for a minute and consider why caffeine is biologically active in most life forms
including those as diverse as plants, insects and human beings.
Why Do We Say that Caffeine is a Universally
Biologically Active Molecule?
Do you remember from your biology class when you learned about ATP (adenosine triphosphate)? You
probably learned that it was an important energy carrier for most living cells. The adenosine molecule is a primary
component of this ATP molecule. You also probably learned that most DNA molecules, including our own, are made up of
adenosine in part. Thirdly, you may have learned in biology that the cyclic ATP (cATP) cell signal molecule
consists, in part of adenosine. The point is that adenosine is a universal molecule probably used for a variety of
reasons in all living cells. How does this all relate to caffeine? The caffeine molecule is structurally similar
to the adenosine molecule. It can mimic the adenosine molecule and is quickly accepted into the living cells of most
life forms. Certainly the human body is no exception.
Before we go on to discuss how caffeine affects I would like to put this information into
perspective. Most of this information refers to coffee drinkers rather than tea drinkers. It simply may not be
applicable to green tea drinker that consumes 2-3 cups per day. For one thing, the amounts of caffeine ingested
in green tea and even black tea is much smaller and in a less provocative form than found in coffee. For another
thing, green tea contains a natural calming agent, theanine, that places a lid on caffeine's effect in the brain.
Nevertheless, I find it the effects of caffeine in the brain very interesting and I share the following anticipating
that you will too. Again, the following applies to the coffee drinker and may not apply to the green tea drinker:
What Does Caffeine Do in the Human Brain?
In order to understand how caffeine stimulates the brain, we must consider a little neurophysiology
and the role of adenosine in neuron activity. As our brain cells do their thing, they release as a byproduct
adenosine. When adenosine is present around neurons, it signals the neuron to slow down. We associate increases
in adenosine with fatigue. Adenosine is a primary signal for the brain cells to slow down. In this way, after
many hours of activity, the brain cells get sluggish and are less functional with increasing amounts of
adenosine. Adenosine signals the brain cells to slow down like our key unlocks our front door or turns on our
vehicle. Most, if not all, brain neurons have adenosine receptors on their surfaces. Adenosine works by combining
with these surface adenosine receptors. Just as the correct key is accepted by the lock on our front doors, these
adenosine receptors accept only the adenosine molecule with one exception, caffeine. When we want to unlock our
door, we put the key in the lock and remove it. When the adenosine molecule works on the adenosine surface
receptors it is inserted but then removed. But when the caffeine molecule is inserted into the adenosine receptor
it hangs out there. This is a little like someone sticking a toothpick into our door lock. The lock will not
accept the key. Likewise, the adenosine receptor will not accept the adenosine molecule if a caffeine molecule is
stuck in it. The neurons or our brain depend on adenosine entering the receptor to signal it to slow down and to
experience fatigue. If caffeine is present, the signal to slow down is muted. That is, the primary signal for
the brain neurons to slow down is distorted. Caffeine molecules blunt the neuron's primary signal to slow
down. The result is increased and prolonged neuron activity. Caffeine dulls the signal to slow down.
I began this seminar by describing my brain feeling like a large clot when I wake up in the
morning. I said that the caffeine in my brain seems to release something. I described this release as an
increased flow of fluids in my brain. Here is what I believe is happening.
How Does Caffeine Speed Up Neuron Activity in the Brain?
When brain cells are active, they release larger amounts of neurotransmitters, brain chemicals,
to stimulate one another. As they become more and more under the influence of adenosine, they release less
neurotransmitter which provokes reduced stimulation. For example, when brain neuron #1 is inactive, its floodgates
are blocked and it is unable to stimulate its neighbor, neuron #2. When brain neuron #1 is active, its floodgates
are open and neurotransmitter is released in ways that stimulate neuron #2. Of course, when neuron #2 is stimulated,
it stimulates neuron #3 by releasing neurotransmitter. When adenosine receptors on neuron #1 are filled with
adenosine, the floodgates for neurotransmitter release are closed. But when these same receptors are filled with
caffeine, the floodgates are opened. Caffeine, therefore, has the effect of opening the flow of neurotransmitter
from neuron #1 to neuron # 2 which then releases neurotransmitter to neuron #3 and so on. More caffeine, more
neurotransmitter release and (up to a point) more brain activity; more adenosine, less neurotransmitter release
and less brain activity. In effect, caffeine improves neurotransmitter flow in the brain. Increased
neurotransmitter flow is associated with increased information flow in the brain. We can see how caffeine stimulates
our brains.
But I also said that caffeine altered my perception. Not only was my brain more active after my
caffeine fix, it also changed the way I looked at the world. I attribute this altered perception to the increased
activity/flow of three different neurotransmitters: norepinephrine, serotonin and acetylcholine.
Can Caffeine Serve as an Antidepressant?
Some of the old style antidepressants are the tricyclic compounds which are believed to
work, in part, by increasing norepinephrine activity. Norepinephrine activity in a central part of the brain
called the amygdala is important for improved emotions. Amygdala activity appears to play critical roles in our
overall emotional states and our memory systems. I believe that one reason my perception is favorably altered
after my caffeine hit is that my amygdala increases its activity. Increased levels of norepinephrine in my
amygdala, prompted by caffeine, probably improves my world outlook and my ability to remember things.
Most of the new style antidepressants are selective serotonin re-uptake inhibitors. These agents
slow down the removal of a key neurotransmitter in the brain, serotonin. Under the influence of these antidepressants,
released serotonin has a more prolonged and greater effect in the brain. Another key very basic component of the
human brain is a group of neurons called the raphe nuclei. This group plays an important role in how we perceive
pain. These neurons are also key stimulators of the cerebral cortex where most of our thinking takes place. The
raphe nuclei neurons also stimulate activity of the limbic system, where much of our emotional circuitry is
located. Furthermore, these neurons are important stress mobilizing brain components. I believe that caffeine
indirectly increases the level of serotonin in my raphe nuclei. In so doing, I believe, it (1) makes me less aware
of pain, (2) stimulates my cerebral cortex, (3) improves flow in my limbic system and overall world view and (4)
mobilizes stress hormones so I am better able to cope with the stressors of my life.
Can Caffeine Enhance Our Memory?
The neurotransmitter acetylcholine appears to play a critical role in the formation of new
memories. In particular the neurons of the basal nucleus of Meynert and those of the interpeduncular nucleus
are important for memory and recall. For example, the nucleus of Meynert is typically diminished in senile
dementia and Alzheimer's patients with reduced amounts of acetylcholine. I believe that caffeine helps me learn
and remember faster because it increases the flow of acetylcholine in nerves making up these critical parts of my
brain, my basal nucleus of Meynert and my interpeduncular nucleus.
How About a Summary of What Caffeine Does in our Brains?
So, what does caffeine do in our brains? From my understanding I believe that caffeine minimizes
the effects of the neurotransmitter GABA, our natural brain tranquilizer. This would have the effect of slowing the
natural breaking system in the brain and the flow of information through the brain would be facilitated. I also
believe that caffeine works to increase levels of norepinephrine, increase serotonin levels, and increase acetylcholine
activity in certain critical parts of the brain associated with the feeling of well being and those associated with
short-term memory.
A lot of this is conjecture of course. I have no proof that the caffeine in my green tea and espresso actually does
these things to my brain. Nor do I want to venture into the private territories of your individual brains. I do know,
however whether my improved confidence, memory and world view consistently takes place with my morning caffeine
fix. Whether this is placebo or actual, anyone who knows me will validate that my mentality significantly improves
after I consume green tea and espresso. I have no idea if this phenomenon works in you or not.
Can Caffeine be Addicting?
The interaction between adenosine/caffeine and the adenosine receptor is only half of the
story. When caffeine is consumed regularly and the neurons have frequent difficulty in receiving their signal
to slow down, they increase their sensitivity to adenosine. They do this by adenosine receptor upregulation.
That is, they make more adenosine receptors. This is like creating more ears when things are harder to hear.
With greater numbers of adenosine receptors on the neurons, the brain becomes more sensitive to their signals to
slow down. With more receptors, natural amounts of adenosine have the effect of making the brain sluggish. The
flow of neurotransmitter and associated information is slowed. At that time the addicted individual needs
caffeine to counter this effect. On the other hand, if the individual goes without caffeine for a few days, the
neurons sense this and begin to downregulate. That is, they produce fewer adenosine receptors. With fewer
adenosine receptors, the neurons are less sensitive to their natural breaking system and they begin to naturally
release more neurotransmitter with the overall affect of increasing brain activity. We can see that the brain
neurons adjust their overall sensitivity to natural adenosine related to how much and how regularly one consumes
caffeine.
But the brain's adaptation to caffeine by making more adenosine receptors is only part of the
caffeine addition process. Two other points I would like to make.
What About Caffeine Causing Cerebral Vasoconstriction?
Caffeine promotes vasoconstriction in the blood vessels lying under the skull and which serve
the brain. By vasoconstriction I mean that they narrow and less blood goes through them. These blood vessels
do not appear to adapt as the brain cells do. Vasoconstriction occurs consistently over many years every time
caffeine is ingested. They do, however, undergo vasodilation within 24 hours of not using caffeine. By vasodilation
I mean that they enlarge, let more blood pass through. But they enlarge in a very confined space between the hard
skull and the brain. Brain blood vessel vasodilation is associated with headaches. For example, the massive
vasodilation of brain blood vessels is the basis for migraine headaches. This is why caffeine may be used
successfully to promote vasoconstriction relieving the headache. In this way, in the caffeine addicted
individual, caffeine withdrawal tends to promote brain blood vessel vasodilation and associated headaches. These
minor, migraine-like headaches tend to last for several days. At the end of this time, so long as the individual
stays away from caffeine, the brain's blood vessels return to normal and the caffeine-withdrawal headache goes away.
Can Regular Caffeine Consumption Early in the Day Facilitate Sleep?
If one consumes coffee caffeine only in the morning, as I do, I believe that it can have
a beneficial affect. I assume that my triple espresso in the morning promotes the upregulation of adenosine
receptors. But as the affects of this caffeine wares off in the early evening, adenosine receptors are increasingly
sensitive to adenosine slowing the brain down. Furthermore, I would assume that GABA is increased further slowing down
the brain. Likely, other brain chemicals that tend to excite the brain would be reduced as well. I believe that all
of these factors?adenosine receptor upregulation, increased GABA, reduced norepinephrine and other excitatory
neurotransmitters?help me get a good night's sleep. I believe that all of these factors come into play when I lay my
head on the pillow and quickly close my eyes to go to sleep. Now, whether or not this affect would work on anyone else
or not, I do not know. Of course, coffee caffeine consumed late in the day typically keeps me awake in a most uncomfortable way. I tell this story because I believe my morning caffeine fix and coffee caffeine withdrawal for the remainder of the day actually helps me sleep.
Next, I would like to return to caffeine amounts as they relate to drinking tea. I would like to
offer one possible explanation to the following question.
What Factors Determine Caffeine Levels in our Teacups?
I believe that there are several factors that come into play that determine how much caffeine ends up
in our teacups. I would like to consider the following seven. Here, I present more information to those factors that I
believe are most important.
• Genetic Variety The genetic variety of the Cs plant plays a role in how much caffeine is in the plant parts
used to make tea. Biologists often call these genetic variations of the same species, "subspecies;" gardeners, "varieties"
and tea professionals, "jots."
• Cs Parts Selected The parts of the plant selected for making tea also plays a role in how much caffeine is in
our teacup. We said earlier that the more rapidly growing tips and first leaves typically contain a greater proportion
of caffeine than the more mature stems and leaves sometimes used for manufacturing tea.
• Agriculture Growing conditions, especially during the flushing process, play a role in caffeine levels in both
manufactured tea and brewed tea. For example, nitrogen added to the soil tends to promote both flushes and higher
caffeine content.
• Manufacturing Process Manufacturing conditions likely play a role in determining the caffeine content of
tea. For example there may be variations in caffeine content associated with withering time. Up to a point, some
withering appears to increase caffeine content whereas if the withering process is extended the tea content appears
to diminish. At the same time, fermentation conditions, especially fermentation time and temperature, appear to play
a role in the caffeine content in the manufactured tea. Generally, increased fermentation time and temperature appear
to diminish the caffeine content.
All four of these factors probably play less significant roles in determining caffeine content in manufactured
tea. Probably the three most important conditions that determine the amount of caffeine in the teacup are caffeine
availability, brewing time and brewing temperature:
• Availability of Caffeine in the Cs Plant Parts to the Brewing Water I believe that one of the
most significant factors is how much the cellular structure is broken down during the manufacturing process. For
example, in order to make black tea, the plant cells are purposely rolled, smashed, cut or torn to activate the oxidative
enzymes. In contrast, green tea cells are preserved as much as possible during the manufacturing process. Typically
green tea flushes are hand picked, and treated gently in order to bring to the tea cup as much as possible the conditions
of the life when picked. Recall, that when the flushes are picked that the caffeine is largely sequestered in the
large, aqueous vacuole of each cell. During typical manufacturing conditions of black tea, these vacuoles are largely
disrupted. The cell sap from these vacuoles is exposed and ooze out over the tea surfaces. The caffeine, along with
the flavorful polyphenols of tea, comes to the leaf surfaces. As the tea is dried, water loss results in the drying and
formation of caffeine/polyphenol crystals largely at the leaf surfaces. Placed in the brewing water, both caffeine and
polyphenols are immediately available. Caffeine is very soluble and needs only the available brewing water to become
part of the brew. On the other hand, with green tea, most of the caffeine is still inside now-dried vacuoles. In order
for it to enter the brewing water it must first pass through a largely intact layer of dried cytoplasm and cell wall
material. And, many of these cells are deep within the leaf or bud and cellular caffeine must find its way through all
of these cells to the brewing water. We can see that manufactured black tea and green tea may have the same caffeine
content but it passes more rapidly from tea to brewing water in black tea. I offer this hypothesis and one explanation
as to why brewed black tea typically contains more caffeine than brewed green tea. It is more available to the brewing
water in the former; less available in the latter.
• Brewing Time I believe that there is another significant variable in determining how
much caffeine is in our teacup. The longer the brewing time, up to the point of depletion, the more caffeine enters
the brewing water of our tea. This is not a new hypothesis but one that I embrace. Brew a specific tea, black,
green or other Cs tea, one minute and it will deliver less caffeine to the cup than if the same tea is brewed for five minutes. One of my greatest pleasures in life is to serve green tea to guests after dinner and with a desert. Knowing that most will not want a lot of caffeine, I will brew it for 1-2 minutes. I know that the brewing process has not developed completely but I prefer this method of minimizing caffeine content over decaffeinated tea. It seems more natural to me somehow. I serve the green tea with the statement, "Here is a lightly-brewed, slightly-caffeinated green tea." I also enjoy adding a few comments about where the tea came from. I also admit to welcoming the opportunity to tell our guests more about tea. On the other hand, when serving green tea with breakfast, I brew it longer. At that time, I want the flavors to be fully developed and am less concerned about the still small amounts of caffeine in the brew.
• Brewing Temperature Another factor that likely plays a potential role in determining tea
cup caffeine is brewing temperature. I say potential because, theoretically, the hotter the brewing water the more
rapidly the transfer of caffeine from tea to water. But all of us know that most green teas need to be brewed at
similar temperatures. A temperature I strive for when brewing green tea is 180o F. I am sure each of you will have
your own preference regarding brewing temperature but most of us strive for brewing temperature close to this when brewing
green tea. At the same time, the laws of Physics suggest that we will find more caffeine in the cup of green tea brewed
for three minutes brewed at 210o F than at 180o F.
To summarize, the genetic variety, selected plant parts, growing conditions, manufacturing
conditions, breakdown of cell structure, brewing time and brewing temperature all play a role in determining how
much caffeine is present in our brewed tea. Also, I offer the hypothesis that greater caffeine availability to the
brewing water is a major reason why brewed black tea typically contains more caffeine than brewed green tea.
Will the Decaffeination Process Reduce the Potential Health Benefits of Green Tea?
It appears to me that more and more individuals want to benefit from the healthy qualities of tea but avoid its
caffeine. It also appears that over the years, we have gotten better at decaffeinating it. How do we decaffeinate
Cs teas?
More and more teas are being decaffeinated using the supercritical carbon dioxide method. I prefer this
method. Here, dry, manufactured tea is placed into a chamber, the chamber closed and cold carbon dioxide gas is
pumped into the chamber at extreme pressures. By regulating the temperature, the carbon dioxide arrives at a semi
liquid-semi gaseous state. In this physical state the carbon dioxide becomes an excellent solvent for carbon dioxide
molecules. By regulating the pressure and temperature the caffeine enters this solvent much more rapidly than the polyphenols of tea. Most of the polyphenols, including the catechins, remain with the still dry tea; most of the caffeine exits the tea and enters the carbon dioxide solvent. The carbon dioxide, now containing caffeine, is pumped out of the chamber. This method also, in large part, maintains the integrity of the leaves, buds and cells. It looks the same and maintains most of its flavorful and healthful compounds without the caffeine.
But here is where my prejudice comes in. Decaffeinated tea is processed tea. To me, the most redeeming quality of any
tea, and especially green tea, is that the tea pickers and manufacturers go to great lengths to maintain the qualities of
the living tea flushes. Yes, I find something missing in decaffeinated tea. To me, decaffeinating tea is like a frontal
lobotomy. The most interesting parts of the tea's personality are gone. And then to have to pay more for this process
is more than I can bear. This is especially difficult for me because I know that most decaffeinating companies sell the
caffeine, for good prices, that was removed from the tea.
There's more. Much of the time the decaffeination process used is unavailable. Certainly the critical carbon dioxide
method leaves no measurable residue. But maybe other solvents were used. I can't imagine removing caffeine from tea
using XXX or XXX without there being some residue that ends up in my teacup. This concern is probably my paranoiac
mentality more than my scientific mentality but I do have a choice. My choice is to drink teas that are as like the
living flushes as is possible.
Are There Potential Health Benefits of Caffeine?
Are their healthy attributes of caffeine? I believe so. I offer five reasons why I say this.
• Caffeine users, especially coffee drinkers over tea drinkers, tend to be less depressed than
caffeine abstainers. I know for myself, and others around me will agree, I tend to become depressed when I try to go
without caffeine in the morning. There are several studies that bear this out as well.
• Caffeine tends to promote the release of the body's natural energizing hormones such as
epinephrine (adrenaline) and norepinephrine. These hormones tend to promote increased physical activity and increased
energy expenditure. There are some studies that caffeine users, assuming the same carbohydrate consumption, are less
likely to put on weight than caffeine abstainers. A key part of this hypothesis is that the individuals consume the
same amount of carbohydrate calories. I restate this because other studies suggest that tea drinkers, often more health
conscious, tend to gain less weight because they curb their carbohydrate-caloric intake.
• Caffeine also may increase insulin efficiency. Increased insulin efficiency tends to lower blood
sugar levels. Some studies suggest that caffeine consumers tend to develop diabetes less frequently than caffeine
abstainers given the same carbohydrate caloric intakes. If this is true, and it resonates from my own experiences, a
caffeinated beverage and scone will not increase blood sugar levels as much as the scone and a cup of water.
• Caffeine appears to have some antioxidant qualities. Most of this is due to the primary caffeine
breakdown product uric acid which has significant qualities. Theoretically, caffeine users will have a greater ability
to quench (mute) harmful oxidants than caffeine abstainers. In my opinion, the caffeine in green tea is supportive of the
catechins and other polyphenols that appear to promote human health.
• Caffeine has the potential to be an anticancer agent. There are studies with animals suggesting
that caffeine placed on the skins of animals exposed to UV light are substantially less likely to develop skin cancer
than those exposed without the caffeine. Certainly more research is necessary before anyone can call caffeine an
anticancer agent. On the other hand, the evidence tips toward cancer prevention rather than cancer promotion.
Are There Potential Adverse Health Affects of Caffeine?
Yes, especially if too much is consumed. From my perspective one can overdo any good thing to
make it a bad thing. Small amounts of iodine are necessary for normal thyroid function; larger amounts can be
toxic. There are many examples of this phenomenon. On the other hand, even small amounts of caffeine are
potentially unhealthful.
• Pregnancy Pregnant women do not metabolize (eliminate) caffeine as efficiently as
they would when not pregnant. The normally high progesterone levels in pregnancy appear to interfere with the
usual caffeine processing in the liver. Even more, caffeine in the pregnant women's bloodstream efficiently
passes through the placenta into the circulating blood of the fetus. The fetal liver is unable to process the
caffeine and it continues to circulate until it passes through the placenta in the other direction. In this way, the
fetal blood can contain prolonged, high levels of caffeine. I would also like to remind you that at high levels,
probably unreached in the fetus, caffeine can slow the growth of germinating (growing) plant cells. What mother would
want to do anything that could negatively affect her vulnerable baby?
• Sleep Caffeine can interfere with normal and healthy sleep patterns. I don't know about
you but no one seems to be around me the next day if I don't get my necessary sleep. Study after study suggests that
many people don't get sufficient amounts of sleep and this can lead to anger, anxiety and bad attitudes. These are not
indicators of good health, mentally or physically. Ingesting high amounts of caffeine such as drinking numerous cups
of coffee even in the morning are still in sufficiently elevated levels to interfere with needed sleep. Even ingesting
small amounts of caffeine late in the day can also interfere with sleep. Caffeine-deprived sleep certainly sets the
stage for unnecessary stress during the day. In many individuals, undue stress leads to poor health.
• Blood Flow Reduction to the Brain Even relatively small amounts of caffeine tend to
promote mild ischemic conditions in the brain. We discussed earlier how caffeine promotes vasoconstriction in the
blood vessels serving the brain. By ischemic, I mean that the blood flow is reduced. Interestingly, my research of
the scientific literature suggests that there are more advantages to have caffeine in the circulating blood during an
ischemic-based stroke than disadvantages. I would have thought to have found the opposite. Nevertheless, reducing
the blood flow to the brain has the potential to be unhealthy and this is why I include it here.
• Exacerbation of Glaucoma Caffeine tends to promote ischemia in the blood vessels that
drain the watery fluids inside the eye. Normally, there is a balance of fluids entering the eye and exiting the
eye. These fluids provide rigidity to the otherwise collapsible eyeball wall. Vasoconstriction of the blood vessels
that remove fluid from the eyeball can cause increased intraocular pressures. When sufficiently high, in glaucoma,
the eyeball wall is expanded with the loss of nerves and vision loss.
• Interruption of Natural Cardiac Rhythms Caffeine, especially in high amounts, can cause
cardiac rhythm irregularities. This phenomenon is poorly understood but probably related to the increased levels of
adrenalin and other stress hormones sometimes associated with caffeine intake.
• Caffeine Anxiety Caffeine, even in small amounts, is capable of producing apprehension
and anxiety in some individuals. Perhaps further research will help us understand what is behind this phenomenon.
I want to tell you how easy it would be for me to say that there are not sufficient levels of
caffeine in 2-3 cups of green tea to cause any health problem for the individual. Indeed, virtually all of the
studies suggesting the unhealthy qualities of caffeine are of coffee drinkers and from non-tea sources. I am
unwilling to go that far, however. I believe in the individual and that there are huge variations between different
individuals. Each individual probably knows whether caffeine, even in the small amounts associated with green tea,
is best for them. In addition, there are probably many individuals who are sensitive to even small amounts of
caffeine. What is right for one person may not be for another person.
Thank you very much for your interest in caffeine. Thank you for your time. I would like to
entertain any suggestions or questions you care to offer."
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