oh that hot cup of morning Joe caffeine is often cited as the most widely used
drug in the world it's a naturally occurring substance found in plants and
foods and both organic and processed foods caffeine though is a stimulant
that works by blocking adenosine inside your cells and here's how this works
adenosine is produced in the cells of the brain in other organs and it's it's
a chemical that's involved in inducing or bringing on sleep by slowing the
activity of the cell caffeine is similar in structure to the adenosine molecule
so when you drink coffee and digest it the caffeine in the coffee travels to
your brain and binds to the cells and blocks the adenosine from binding
without the adenosine to slow things down your adrenal glands get the signal
to release the fight or the flight or fight hormone epinephrine epinephrine
also known as adrenaline then acts to increase alertness increase your heart
rate and constrict blood vessels so this is the high that you get from caffeine
it's that boost of adrenaline also as an aside the constriction of blood vessels
that follow the caffeine consumption is the basis for caffeine being a part of
headache medicines it constricts the blood vessels in the brain through the
epinephrine release which gives the tissues more space and relieves some of
the tension that was producing the headache so back to the caffeine and
sleep caffeine affects your sleep in a couple of different ways first it
extends your sleep latency which we know is the time that it takes for you to
fall asleep it also shortens the total amount of time that you sleep and the
older that you get the more sensitive you are to these
effects similar to alcohol caffeine is a diuretic which causes the body to lose
water so how much caffeine does it take to affect your sleep depending on the
amount of time between consuming the caffeine and going to sleep I'd say
anything greater than 200 milligrams of caffeine would create a delayed sleep
effect a moderate dose of caffeine would be anything between say two hundred and
three or four hundred milligrams a day heavy caffeine consumption would be
considered around 500 milligrams a day so what does that mean exactly well
let's look at typical caffeine concentrations in foods as you can see
there's a lot on this page but I just wanted to point out a few things to give
you a ballpark of what kind of things we consume and how it compares to a
moderate caffeine consumption or low or high so if you're one you like Starbucks
Coffee you can see that the smallest on the short is a hundred and eighty
milligrams which that's just a little under what under the 200 which is a dose
that can delay your sleep but if you prefer the grande version of it the 330
milligrams now you're into a moderate dose of
caffeine also everything else on this list
is lower in concentration than coffee including Mountain Dew which I'd always
heard was what you needed to drink if you really needed to stay awake but you
really need to drink a few of them as Mountain Dew with 12 ounce can only
contains about 55 milligrams of caffeine which is less than a cup of coffee and
another thing on this list that I thought was significant is the Hershey's
chocolate bar I have here that it's one and a half ounces for sorry four for one
and a half ounces of the bar you get nine milligrams of caffeine well okay if
that if you can discipline yourself to only eat one of those little squares but
for an eight ounce bar the kind that you buy in the store
now you're getting 46 milligrams of caffeine you know that's not a huge dose
of caffeine but it may make a difference if you were to have that in the evening
say as opposed to in the morning keep in mind imported coffees and teas
usually carry a higher caffeine concentration and the brewing method
that you use can affect the caffeine content once you consume the caffeine
its digests it through the stomach and small intestines and enters the
bloodstream within 30 minutes to an hour and this is a relatively rapid response
and in fact this is one of the reasons why a cup of coffee is so popular as
that morning kick to get you going let's look at some of the negative effects of
caffeine we have reduced appetite insomnia rapid or racing heartbeat
anxiety headache nervousness irritability and you can have
gastrointestinal problems like nausea or diarrhea the half-life is the amount of
time it takes for something to decrease to half its original quantity the
half-life of caffeine varies among different studies but this generally
believed to be somewhere between three and a half to
six hours it can take longer in some people with certain medical disorders or
who are under the influence of certain medications for example birth control
pills can inhibit or slow the half-life of caffeine making it so that it takes
five to ten hours for the amount of caffeine in your bloodstream to decrease
by half pregnancy and liver disease can also significantly extend the half-life
of caffeine so let's look at a practical example suppose you were to drink at all
Starbucks coffee at 9:00 a.m. that size has 230 milligrams of caffeine if we
assume the caffeine carried a half-life of 5 hours you'd have approximately 130
milligrams of caffeine in your system at 2:00 p.m. that afternoon just from that
single cup of coffee and at 9:00 o'clock in the morning now this is an
approximation but because of the variability in how we metabolize
caffeine some experts recommend that that you not consume any caffeine after
noon and I happen to be in that camp I usually recommend to people that you
have your last drink of coffee before 12 o'clock in the afternoon but I realize
there are those people who are able to drink tons of coffee even in the evening
and never seem to have trouble falling asleep
and we really still don't know everything about caffeine even experts
are unsure as to whether the varied responses are because of tolerance cut
to the caffeine or it could simply be that some people metabolize caffeine at
a faster rate and and are therefore less sensitive to the sleep interfering
properties my own thought is that people who drink caffeine or drink coffee after
6:00 p.m. probably are not planning to go to bed 3 hours later
and it may just be that those people who do drink numerous cups of coffee
throughout the day and continue into early evening of this tolerant to the
stimulating effects of the caffeine and because they normally fall asleep later
in the evening they're just not aware that it's the caffeine is actually