The Effects of Caffeine on Your Brain
What's the latest evidence say about the effects of caffeine
on your brain? You may recall a report in the newsletter a while
back about studies which show an increase in academic test scores
for students who have a cup of coffee. I have probably also mentioned
that too much caffeine, especially once a person is addicted
to it, tends to make clear thinking less likely. So is that tea
or coffee good for your brainpower or bad for it? Let's take
a closer look.
Caffeine is a stimulant, meaning it accelerates physiological
activity. Specifically, it speeds up the action of your brain
and makes you more alert. It does this by binding to adenosine
receptors in the brain. Normally the chemical adenosine binds
to these, causing drowsiness by slowing down nerve cell activity.
The caffeine doesn't have this effect, but does get in the way
of the adenosine.
Because the caffeine is blocking the adenosine receptors,
your neurons become more active than they otherwise would be.
That is why it sees to be good for the brain. Then your pituitary
gland responds to all the activity as though it was an emergency,
by releasing hormones that tell the adrenal glands to produce
adrenaline. This is what is sometimes known as the "fight
or flight" hormone (and is also called epinephrine). This
release of adrenaline causes:
* A faster heart rate.
* An opening up of breathing tubes.
* A release of sugar into the bloodstream from the liver.
* A readying (tightening) of muscles for action.
* An increase in blood flow to muscles.
Essentially all that adrenaline makes you tensed and ready
for action, but not necessarily intellectual action. You do become
more alert initially, and your brain may work better and faster.
But by the time you start that second cup, you may be anxious
and irritable, which is not conducive to clear thinking. Is there
a balance that works?
Studies which demonstrate an improvement in mental function
usually show it after one eight-ounce cup of coffee. Other studies
show that drinking two cups (versus none) causes irritability
and an increase of the heart rate by 15 to 20 beats-per-minute.
So if you must use caffeine, try to limit it to one cup. Tea
has less than half the caffeine of coffee, so you may want to
switch if you want to enjoy more to drink without getting that
racing heart.
Some self-experimentation is probably called for, especially
since we don't all react in the same way to caffeine. But there
is also more to the story.
Other effects of caffeine on the brain include an increase
in dopamine levels, much like that caused by amphetamines or
heroine (but without such a pronounced effect). Dopamine is a
neurotransmitter which activates the pleasure centers of the
brain. It is suspected that this is part of the reason caffeine
can be so addicting. Alert and happy? You can see why your body
and brain likes the stuff. The problem, though, is that long
term it can have some pretty nasty effects.
For example, once the adrenaline wears off, you can feel depressed
and tired. This causes you to crave more caffeine, of course.
The problem with that is that it interferes with proper sleep.
It is estimated that the half-life of caffeine in your body is
about six hours. This means that if you have a large cup of coffee
(12 ounces) at four in the afternoon, with about 150 milligrams
of caffeine, and then go to bed at ten, you still have about
75 milligrams of caffeine in your system.
That may not keep you awake. In fact, some people can sleep
with several hundred milligrams of caffeine in their bodies.
But that blocking of adenosine receptors will prevent deep sleep,
which you need. As a result you are tired the next day and so
you reach for more coffee, starting a downward spiral of addiction.
Start the cycle and you find it tough to stop.
This explains why for many people, like myself, regular caffeine
consumption makes for almost constant tiredness. Being tired
and/or irritable does not help one's brainpower. Those of you
who have quit a caffeine addiction know that the withdrawal can
bring aches, depression and extreme tiredness and give you a
terrible, splitting headache as blood vessels in the brain dilate
(the caffeine keeps them constricted).
Quitting caffeine is painful, but I recommend it for anyone
who wants to be a better thinker. If you can have the occasional
cup of tea or coffee or cola without becoming addicted, you can
use it as needed and get some real benefit. But with regular
use the effects of caffeine are generally negative.
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