#9 - Caffeine: History, biological mechanisms, and impacts on sleep

There are a few drugs that are so socially accepted that we often forget their risks. Alcohol may fall into that category for some, but caffeine falls into that category for most, as an astonishing 90% of the world drink coffee daily. Caffeine is in fact so prevalent in our bloodstreams that it is also a part of our identity. If that sounds like an exaggeration, think back to the last time you heard somebody say “I don’t feel like myself today” after not getting their morning coffee. How was this drug able to establish such a foothold in society, and what are the risks that have come with it?

Coffee beans began being discovered in different regions of the world at different times, it was not one coherent discovery that spread around the world. What seems to be a common trend is that wherever it was brought, society was changed in obvious ways. Ninth century traders brought it to the middle east, around the same time as the Islamic golden age. China experienced its golden age after the Tang dynasty popularized tea. The scientific period in Europe had its breakthrough at around the same time as coffee began being traded there, in the 16th century. The link between coffee and knowledge was then developed further in Europe as coffee shops began to be hubs for knowledge.

What can explain this clear correlation between caffeine and intellectual advancement? What effect does caffeine have on the brain and body?

Central Nervous System Stimulation: Caffeine primarily works by blocking the action of a neurotransmitter called adenosine. Adenosine promotes sleep and relaxation, and its levels gradually increase in the brain as you become more awake throughout the day. By blocking adenosine's effects, caffeine promotes wakefulness and alertness.

Increased Neurotransmitter Release: With adenosine blocked, other neurotransmitters like dopamine and norepinephrine become more active. Dopamine is associated with pleasure and reward, while norepinephrine is linked to the body's "fight or flight" response, increasing alertness and energy.

It’s worth noting that caffeine can also increase physical performance by stimulating the release of adrenaline, which can lead to improved endurance and strength during physical activities. However, the negative aspects of caffeine are also important to highlight, not least in regard to sleep.

As mentioned, caffeine blocks the action of adenosine, a neurotransmitter that promotes sleep and relaxation. Therefore, caffeine becomes an obstacle to sleep. Even if you are able to fall asleep with the effects of caffeine active in your system, it could be worsening your sleep quality (which is as important as sleep duration) by stopping you from reaching deep sleep.

Caffeine has a half life of about 5-6 hours. Therefore, if you go to bed at 11 pm and you have a cup of coffee with 100 mg of caffeine (a normal coffee) at 6 pm, it would have the same effect as drinking half that cup of coffee right before bed. According to sleep scientist Matthew Walker, caffeine should be avoided from at least 8, but preferably 10-12 hours before sleep.

If you experience afternoon crashes on days where you ingest coffee early in the day, it would be wise to skip your first coffee and instead wait about 90 minutes after waking. This is because when you initially wake up, a lot of adenosine is still in your system. If you ingest caffeine before the adenosine can “clear out” then you will get an abnormal amount of adenosine (which promotes sleep and relaxation) when that caffeine wears off in the middle of the day.

Cover image: https://www.news-medical.net/news/20210216/Daily-caffeine-consumption-can-change-the-gray-matter-of-the-brain.aspx