Executive Summary Video
We drink coffee for the quick energy boost it gives. Coffee improves alertness and cognition. However, those positive effects are short-term and wear off once the caffeine is metabolised from our blood.
Over the longer-term, coffee leads to addiction because our body gets used to its energy jolt and craves that higher energy state. The body also gets used to the energy-boosting effects of caffeine and does not respond as strongly to the caffeine intake.
Thus, coffee is great for the short-term but bad for long-term use.
How Coffee Improves Alertness
Our body uses energy by burning a chemical called adenosine triphosphate, or ATP. A byproduct of this mechanism is a compound called adenosine. As the long day wears on, the levels of adenosine in our body keep increasing.
Our brain has adenosine receptors. The molecules of adenosine attach to those receptors. The brain senses the presence of adenosine, once it is bound to the receptors. The more the adenosine, the more is the sleepy sensation.
Caffeine in coffee has a similar chemical structure to adenosine. So after you drink coffee, the adenosine receptors in the brain quickly attach to caffeine. This prevents adenosine from binding to them. As a result, the brain cannot detect the presence of adenosine.
While caffeine is present in the blood, the brain stays alert as if there is very little adenosine in the system. It is as if our body is rested and fresh.
After you drink coffee, the caffeine levels reach their peak within 45 to 60 minutes. They stay high for 6 hours and they are cleared from the body in 10 hours. As the caffeine comes off, the brain starts sensing adenosine levels again, which would have increased some more in those few hours. As a result, you will feel even more sleepy.
Over a period of time, our bodies adapt to caffeine. The liver starts metabolising caffeine faster. As a result, caffeine is cleared from our system quicker. So the feeling of tiredness starts returning faster.
Faced with the blocking of adenosine receptors, the brain adapts, too. It develops more adenosine receptors. So more adenosine is sensed by the brain even for the same amount of caffeine consumed. Thus, drinking the same amount of coffee no longer gives you the same levels of perkiness.
- Caffeine is also known to reduce insulin sensitivity (and increase insulin resistance) in the short term. This boosts blood glucose levels after drinking coffee. Since the heightened insulin resistance prevents blood glucose from entering cells for energy production, one feels fatigued and tired.
- Coffee is also a diuretic. One ends up passing more urine after drinking coffee. This water loss reduces blood pressure. The heart beats more rapidly to maintain blood flow leading to tiredness.
- A 250 mL or 8 oz. cup of coffee contains 80 mg of caffeine. You should not exceed 400 mg a day. Specific life stages such as pregnancy have separate recommendations. Follow them.
- Since it takes 10 hours for caffeine to completely clear from our system, have your last cup of coffee ten hours, or at least six hours, before your normal sleep time. Else, you will get disturbed sleep.
To Read More
- Cleveland Clinic: Caffeine: How to Hack It and How to Quit It
- US FDA: Spilling the Beans: How Much Caffeine is Too Much?
- Mayo Clinic: Caffeine content for coffee, tea, soda and more
- MedicalNewsToday: Why does coffee make me tired?
First published on: 24th December 2021
Image credit: Andrea Piacquadio on Pexels