• What is Caffeine and How Does It Work?
On average, almost every third person in the world drinks a cup of coffee every day[1]. If 100 mg of caffeine per dosage is the average, this would result in over 225 metric tons of it (caffeine) consumed daily, worldwide. It is completely needless to state that caffeine, and coffee in general, are seen as a necessities by millions, if not billions. The drink itself is said to have originated in Yemen, during the 15th century[2]. According to the legend, a sheikh called Omar was in exile and starving when he came across the coffee plant. In the most common version of the story, he found the fruit bitter and decided to throw them into a fire to soften the taste. As the beans have gone solid as an effect, he decided to boil them in order to soften them. The resulting potion bearing resemblance of today’s coffee got him his exile order revoked[3].

Today, caffeine is the worlds most consumed psychoactive drug, given that this substance brings about changes to the function of the brain. Besides the natural source, caffeine can also be produced synthetically, in laboratories. The main mechanism in which this CNS stimulant works is through blocking the adenosine receptors in cells. Adenosine is a chemical that affects the body in a multitude of way, thus creating a range of different effects when blocked. In the brain, adenosine serves as a inhibitory neurotransmitter, essentially producing tiredness and promoting sleep, while rising in amount with every waking hour[4].
  • Cognitive Effects of Caffeine:
The improvements that caffeine consumption can bring about are not limited to the physical. Caffeine ingestion includes a range of cognitive enhancements as well, such as:
Decreased Rate of Perceived Pain:  A study has found that ingesting as little as 100 mg of caffeine can reduce the extent to which the subjects feel physical pain during exercise, specifically grip-related ones[5].
Decreased Rate of Perceived Exertion: There has been sufficient evidence, from a multitude of studies, to believe that the ergogenic effects of caffeine can in fact attenuate the perception of physical exertion, making the user feel as if the loads require less strain. Although, it must be noted that the decreased rate of perceived exertion has not led to an increase in performance or total accumulated volume during the trials[6, 7, 8, 9].
Improved Reaction Time: Four out of five researches claim that caffeine can result in a decrease of reaction time, meaning that the individual responds faster to immediate events, such as positioning the arms during a fall, to avoid injury[10, 11, 12, 13, 14].
Wakefulness: Acute usage of caffeine has been found to increase arousal in test subjects, and it is said that this substance can be used as an effortless manner to manipulate wakefulness in both children and adults, in varying dosages[13, 15, 16].
  • Physical Effects of Caffeine:
Power Output: While sprinting cycling may not necessarily be aided by caffeine, research has shown that maximal power output and total workload can. While the opinion is mixed regarding dosages as low as 2 mg per kg of bodyweight, most studies agree on higher dosages having effect, most commonly 5 mg per kg. The largest effects were witnessed at 800 mg of total caffeine ingested acutely[17, 18, 19, 20, 21, 22, 23, 24, 25].
Adrenaline: Also known as epinephrine, this is the hormone that is responsible for the “fight or flight” response. Among other things, it increases heart rate and redistributes blood to the muscles. Studies have shown that dosages of 5 mg per kg have managed to increase the concentration of plasma epinephrine in subjects by a significant amount. One study measured the increase at 40% while an second one measured it at fivefold[26, 27, 28].
Lipid Oxidation: Although not very sustainable in the long run, research has shown that caffeine does have a positive effect on lipid oxidation or fat loss, in layman terms. One study witnessed that an indicator of lipid oxidation was increased, while the other two showed that there were more serum- free fatty acids available in the bloodstream, acutely upon consuming caffeine. The unsustainable part was regarding daily dosages. The largest effect was witnessed at 400 mg, although higher dosages may lead to even better results[27, 28, 29].
  • Adverse Effects of Caffeine:
Cortisol Increase: Despite the fact that the scientist don’t completely agree to the amount, an acute increase of cortisol upon consumption of caffeine is present, especially in those who aren’t regular coffee-drinkers. The varying results could be due to to differences in dosages and time of ingestion, as cortisol is known to vary throughout the day. The long term significance of this is yet to be researched[19, 20, 30, 31].
Decreased Insulin Sensitivity: An increase in insulin resistance, and thus a decrease in insulin sensitivity has been shown with caffeine consumption. The cause of this is most probably due to the increase in epinephrine, as insulin sensitivity decrease is one of its’ effects[26, 28, 32, 33, 34].
Increased Blood Pressure: While, again, the scientists and the studies disagree in which ways or amounts the pressure was affected, an increase in blood pressure was found regardless, even in habitual coffee drinkers. One study found that a blood pressure increase was only found in the supine position[25, 26, 34, 35].
  • Caution:
Toxic Dosage: While it would be impossible to overdose on caffeine through coffee, it is more than possible to do it accidentally with supplements in powder form. A dosage of 20-40 mg per kg of bodyweight is more than enough to cause an overdose, and most probably death, on the higher range of this scale[36, 37, 38, 39].
Sensitivity: Caffeine hypersensitivity is usually genetically predisposed but can also come about as a result of the liver being unable to metabolize caffeine molecules efficiently. Simply put, when an individual has a caffeine hypersensitivity, they need a drastically lower dosage to achieve the same effects as their regularly sensitive counterparts. This means that a simple cup of coffee can cause the racing heartbeat people usually get when they take two scoops too many of their pre-workout[40].
Tolerance: As with every other stimulant, the same dosage can never cause the same magnitude of effect in users if taken regularly. This is called tolerance, and it is acquired over time, with some substances being quicker than other in regards of increasing it. As the caffeine intake becomes patterned and increases in regularity, the body becomes more efficient at metabolizing it. This means that the same 100 mg that made your heart race a year ago might be in your cup every morning today. An other thing the body does about caffeine is that it produces more adenosine, in an attempt to reach homeostasis again. This means that the individual is much more tired if they don’t consume caffeine, which in turn creates an addiction. What could be done to avoid this? It’s simple, just refrain from consuming caffeine daily. Even once every other day makes tolerance much more difficult to acquire, and twice or once per week makes it almost- if not completely- impossible[41].


– Milos Askovic

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