Over 100,000 metric tons of caffeine are consumed worldwide every year, equivalent to the weight of 14 Eiffel Towers. Do you remember how you felt after your first cup of coffee? Excitement and a remarkable ability to focus even with a bad night’s sleep - this may explain why caffeine is the world’s most widely used drug. In this article, we explore the chemistry behind caffeine and how it really keeps us awake.
Where is caffeine found?
Caffeine is commonly found in tea, coffee, chocolate, and sodas. The amount of caffeine varies based on the type of beverage we consume and how it’s prepared. Caffeine is the world’s most popular stimulant and is typically associated with happiness and relief. But what really happens when we drink caffeine?
How does caffeine work?
Caffeine is a stimulant for the central nervous system and keeps us awake by blocking one of the body’s key sleep-inducing molecules: adenosine. Our bodies need a constant supply of energy, which they get by breaking down a high-energy molecule called ATP. In the process, it liberates adenosine, ATP’s chemical backbone. Neurons in our brains have receptors that are perfectly tailored to this molecule. When adenosine docks to these receptors, it activates a cascade of biochemical reactions. These cause neurons to fire more sluggishly and slow the release of important brain-signaling molecules. In other words, you get tired.
Caffeine is called an adenosine receptor antagonist. It derails this process of slowing neurons down by blocking adenosine receptors. Caffeine and adenosine have a similar molecular structure, close enough that caffeine can wedge into the adenosine receptors but not close enough to activate it. To summarize, caffeine inhibits the inhibitors, so it stimulates us.
Caffeine can also boost positive feelings; in some neurons, adenosine receptors are linked to receptors for another molecule - dopamine. Dopamine’s role in the brain is to promote feelings of pleasure. When adenosine docks in one of these paired receptors, it is hard for dopamine to fit into its own spot, interrupting its mood-lifting work. However, when caffeine takes adenosine’s place, it doesn’t have the same effect, and dopamine can play its role.
Caffeine’s effects on adenosine and dopamine receptors
Long-term benefits:
Reduce the risk of diseases such as Parkinson’s, Alzheimer's, and some types of cancer
Ramp up the body’s ability to burn fat
Enhance cognition - benefit our mood and focus
Long-term limitations:
May contribute to insomnia and anxiety
Raise heart rate and blood pressure
Caffeine and the brain
Our brains can adapt to regular consumption of caffeine. If our adenosine receptors are perpetually clogged, our body will manufacture extra ones. Therefore, even with caffeine, adenosine can still do its job. This is known as caffeine tolerance, where we may need to consume more caffeine to feel alert since there are more adenosine receptors to block. This also explains the unpleasant withdrawal we may experience if we suddenly quit caffeine because adenosine would work overtime with plenty of receptors, causing symptoms like headaches, fatigue, and depressed moods. In a few days, the extra adenosine receptors will disappear, and our bodies will readjust, even without the inclusion of the world’s most popular stimulant.
Works Cited
EatCultured (2017). The Science of Caffeine. [online] eatCultured. Available at: https://eatcultured.com/blogs/our-awesome-blog/the-science-of-caffeine.
National Consumers League (2016). Get smart about caffeine – National Consumers League – National Consumers League. [online] National Consumers League. Available at: https://nclnet.org/caffeine_facts/.
Patel, K. (2021). The science behind caffeine Article - Examine. [online] examine.com. Available at: https://examine.com/articles/science-behind-caffeine/.
Qasim, H. (2017). How does caffeine keep us awake? - Hanan Qasim. [online] www.youtube.com. Available at: https://youtu.be/foLf5Bi9qXs?si=vDIMywhUzey8Y6Yw [Accessed 29 Sep. 2023].
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