Download The Effects of Caffeine on the Human Metabolism

Madeline Pitman
996522621
EXB 110
April 29, 2013
The Effects of Caffeine on the Human Metabolism
Caffeine is the most commonly used mind altering drug in the world (Moret 1). Caffeine
is found in food, drinks, and drug formations, but most products do not list the caffeine content
(Sepkowitz 243). It is estimated that people consume 16 to 70 mg of caffeine everyday (Moret
1). Since caffeine is so common in the diets of most people, it is important to know how this
drug affects the human body. Caffeine is known to affect the human cardiovascular system, the
central nervous system, modify the metabolism of carbohydrates and modify of the metabolic
rate in humans. The metabolism of an organism is crucial as it affects all aspects of the
organism’s health. There are both positive and negative effects of caffeine on the metabolism of
humans. Due to the fact that caffeine can be beneficial or detrimental, it is important to explore
the effects that caffeine has on the human metabolism.
Any change in the chemical processes inside of a cell is a change in metabolism. For
many years, it has been known that caffeine increases the human metabolism (Spiller 231).
Caffeine can easily effect human cells because it can cross biological membranes with ease,
which allows the caffeine to easily enter cells (Spiller 231). Once inside the cells, caffeine can
then change the rate of the chemical processes in the cell. Depending on the pH of the caffeine,
about 9-22% of caffeine consumed can be absorbed by the human body in just 20 minutes
(Spiller 231).
After caffeine is consumed, it has multiple effects on the human body and metabolism.
The amount of glycerol and free fatty acids increases in the body. The increase of glycerol and
free fatty acids has been shown to have a major effect on the adipose tissues (Spiller 231).
Caffeine can move calcium from cells, which has an affect on the metabolism of a cell because
calcium is used in multiple reactions in cells (Spiller 231). Another important aspect of cell
metabolism is that caffeine affects the plasma protein (Spiller 231). About 35% of caffeine binds
to plasma protein, which would change the way that plasma proteins transport materials
throughout the body (Spiller 231).
Caffeine has a significant impact on the metabolism of carbohydrates and lipids (CanoMarquina 7). Studies have shown that caffeine impairs the glucose disposal in the skeletal
muscle, which results in an increased insulin resistance. This insulin resistance can range from
15-30% (Cano-Marquina 7). The studies that have shown the increased resistance to insulin
have also showed that caffeine did not affect glucose levels.
Caffeine is mostly metabolized in the liver (Cano-Marquina 7). After consuming two to
three cups of coffee, the plasma caffeine levels are about 20-40 μmol/L, which is enough
caffeine to have an antagonist effect on the adenosine receptors. Adenosine receptors are in
almost all tissues in the human body, this includes adipose tissue, the heart, the lungs, and the
liver. By introducing such an amount of caffeine to the human body, the results on the adenosine
receptors may be considerably negative. Adenosine receptors specialize in binding proteins
(specifically Gi or Gs proteins), and therefore change the levels of intracellular cyclic adenosine
monophosphate (camp), change the modulation of phosphodiesterases and the modulation of
intracellular calcium (Cano-Marquina 8). While these results have not been seen in cases in
which coffee is consumed, it is important to consider the effects of caffeine on adenosine
receptors and the effect of adenosine receptors on the human metabolism (Cano-Marquina 8).
Any change in metabolism should be carefully considered because it affects the entire human
body.
An experiment was designed to measure the effects that caffeine has on the time it takes
to complete an exercise over a specific distance (Kovacs 710). An experiment was performed in
which participants were given varying amounts of caffeine, placebo and a carbohydrateelectrolyte solution (Kovacs 712). The varying solutions were given to the participants during a
warm up exercise, and then at one-third and two thirds of the 60 minute time trial (Kovacs 712).
The results of this experiment showed that participants that had the caffeine or the caffeine with
the carbohydrate-electrolyte solution had increased performance metabolisms (Kovacs 713).
While it is interesting that participant’s performance metabolism was increase after consuming a
carbohydrate-electrolyte solution with caffeine, it is not important to consider this result when
considering just the effects of caffeine on performance. The participants that consumed just the
carbohydrate-electrolyte solution did not have an increased metabolic performance, so it can be
concluded that the carbohydrate-electrolyte solution did not affect the performance metabolism
of the experiment participants. The experiment had multiple participants just consume caffeine,
and the results from these participants performance metabolism support the conclusion that
performance is increased when caffeine is consumed. This experiment accredited the
correlation between caffeine and increased performance metabolism with the fact that these
conditions caused an increase in lipolysis and fat oxidation (Kovacs 713). The increased
performance metabolism with the consumption of caffeine was also attributed to the decrease of
muscle glycogen breakdown (Kovacs 712). All of these effects of caffeine consumption are
changes to the metabolism of the body’s cells.
The experiment participants were given a range of caffeine, ranging from 150 mg/l to 320
mg/l (Kovacs 710). When participants were exposed to just 150 mg/l of caffeine, there was an
increase in performance (Kovacs 710). Participants that received 225 mg/l had a greater increase
in performance than those participants that received 150 mg/l (Kovacs 710). Those participants
that received 320 mg/l of caffeine did not experience a further improvement than those
participants that received the 225 mg/l dose (Kovacs 710). This shows that caffeine does
increase performance, but it also shows that excessive amounts of caffeine will not give
increased advantages.
In an attempt to increase energy, alertness, stamina or performance, millions of people
have taken to consuming caffeine in the form of coffee and energy drinks (Sepkowitz 244).
However, since many people are unaware of the amount of caffeine they consume, there have
been several cases of accidental caffeine overdoses (Sepkowitz 244). Caffeine overdosing is a
very serious problem that can lead to serious illness and in rare cases caffeine poisoning can lead
to death (Sepkowitz 244).
While there is considerable evidence that caffeine has an effect on the human
metabolism, not all changes are bad or good. There is reasonable evidence that caffeine
increases performance metabolism in humans. There is also plenty of evidence that excessive
consumption of caffeine can result in serious illness and even death (Sepkowitz 243). When
deciding if the effects of caffeine are beneficial or detrimental to humans, one must consider if
any changes to the metabolism should be considered detrimental. Our metabolisms have evolved
with a specific purpose, and it may not be a good idea to alter the metabolism in any way, as
even the slightest change could have a significant impact on the body. So while there may be
both benefits and drawbacks to consuming caffeine, in the long term it may not be beneficial to
make any changes to the body’s metabolism.
Citations
Moret, Sonia, Manuela Hidalgo, and Juan M. Sanchez. “Simple and Fast Methods Based on
Solid-Phase Extraction Coupled to Liquid Chromatography with UV Detection for the
Monitoring of Caffeine in Natural, and Wastewater as Marker of Anthropogenic Impact.”
ISRN Chromatography. Vol. 2012. 2 Jan 2012. Web. 25 Mar 2013.
Spiller, Gene. Caffeine. New York: CRC, 1998. Print.
Cano-Marquina, A., J.J. Tarin, and A. Cano. "The Impact of Coffee on Health." Maturitas 75.1
(2013): 7-21. Science Direct. Elsevier, May 2013. Web. 25 Apr. 2013.
Sepkowitz, Kent A. "Energy Drinks and Caffeine-Related Adverse Effects." The Journal of the
American Medical Association 309.3 (2013): 243-45. Web. 25 Apr. 2013.
Kovacs, Eva, Jos Stegen, and Fred Brouns. "Effect of Caffeinated Drinks on Substrate
Metabolism, Caffeine Excretion, and Performance." American Physiological Society 85.2
(1998): 709-15. Web. 25 Apr. 2013.