The Chemical Effects of Caffeine on the Human Body
- Science Holic
- Aug 6
- 4 min read
Author: Kayla Otoo
Editors: Oscar Chen, Hwi-On Lee
Artist: Caitland So
From late nights and early mornings to a surplus of assignments, many individuals turn towards caffeine to deal with the daily stresses of life. At a glance, caffeine consumption may seem like a suitable way to rid oneself from all of these stressors. However, this overload of caffeine can in fact lead to more harm than good. Worldwide, this poses an even larger problem as 80% of individuals worldwide consume substances containing caffeine, with countries such as Finland, Vietnam, and Brazil being the dominant producers and exporters of this product. Consequently, it is crucial to understand the pharmacology of caffeine and the potential chemical effects as well as risks associated with abnormal intake to prevent further complications.
Caffeine is created when xanthine and a methyl group coalesce. Also known as 1,3,7-trimethylxanthine (C8H10N4O2), caffeine is an alkaloid compound. Specifically, caffeine is a methylxanthine alkaloid, meaning it contains nitrogen and relates to certain bases in nucleic acids such as adenine and guanine. Known to be the most widely used central nervous stimulant worldwide, caffeine has a 100% bioavailability rate and is highly soluble in water. In other words, almost immediately after ingestion from the gastrointestinal tract, it is estimated that nearly 99% of caffeine is absorbed into the bloodstream within 45 minutes. Then, 10-30% of these caffeine molecules will bind to plasma proteins through a process known as reversible binding. In this process, two molecules bind temporarily and can bind and unbind as many times as they need. Meanwhile, leftover caffeine molecules will be distributed to different body tissues and organs.
After this distribution, caffeine will act mainly as a stimulant by blocking adenosine receptors located in the brain. Adenosine, a neurotransmitter, takes two forms: A1 and A2. These two forms are both from the family of G protein-coupled receptors, which are crucial in cell signaling and also regulate a diverse range of functions in many systems, including the cardiovascular and respiratory systems. As a result, adenosine is primarily reputed for its calming effects, such as relaxation and/or sleepiness. Therefore, caffeine's blockage of adenosine receptors can increase neuronal activity and reverse these calming effects. By releasing certain neurotransmitters such as dopamine, glutamate, and serotonin, an individual will slowly start to feel more awake.
Additionally, caffeine's second primary function is through the inhibition of a family of enzymes known as phosphodiesterases. These enzymes' main function is to break down certain cyclic nucleotides such as cyclic AMP (cAMP). Therefore, caffeine will block cAMP from breaking down within cells. This can lead to many positive effects, such as increased levels of cAMP, which can improve blood flow. However, in some instances, this can cause the aortic wall of the heart to weaken, which could eventually lead to harmful conditions such as an aortic dilation, aka swelling of the aorta.
To determine the potential side effects an individual may experience, it is necessary to understand how caffeine is metabolized. First, caffeine is metabolized by the liver, which occurs through certain enzymes such as CYP1A2, a cytochrome P450 enzyme. The primary pathway for metabolizing caffeine involves demethylation. A huge metabolite in this process is Paraxanthine, which is responsible for over 80% of caffeine metabolism in humans. In the end, caffeine will exit the kidneys via urine excretion. However, this can vary significantly due to many factors such as an individual's age, health, and any possible medication.
All in all, caffeine may seem like a stimulant to help increase attention, yet it often does the opposite and impacts other internal systems. To reduce the potential for harm, it is essential that individuals have insight into their metabolism of this substance. For example, cytochrome P450 1A2, also known as the CY1P1A2 gene, is responsible for the breakdown of caffeine through a process known as demethylation, where a methyl group is removed from the caffeine molecule. However, this breakdown rate differs from person to person due to our varying genetic differences. A person with a fast metabolism may experience less extreme effects than a person with a slower metabolism.
Regardless, excessive caffeine consumption can have negative effects, which can be seen in various studies that prove that heartburn, hypertension, high blood pressure, and other heart-related problems are all possible results from the buildup of caffeine. Furthermore, there is a slight increased risk that caffeine could seep into an individual’s bones, which could contribute to bone diseases like osteoporosis, a weakening of bones, which can interfere with calcium absorption or metabolism. That is why people must start paying careful attention to their caffeine consumption before it becomes an even bigger issue, making it less easy to tackle.
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