Answer
- Coffee reduces tiredness by deceiving your brain that your body does not need rest.
- Once its effect wears off after a few hours, your brain and body are even more tired.
The Science
What is Adenosine?
- After you eat a meal, the glucose in the food is broken down and turned into a chemical called Adenosine Triphosphate (ATP), which helps store energy.
- After ATP is used for your body’s energy needs, it gets converted into another compound called Adenosine.
- A high adenosine level in your blood is an indication to your brain that your body has finished using simple sugars in the food and needs to rebuild its energy storage.
- Your brain has a mechanism whereby adenosine tells brain cells (neurons) to cease activity, making you drowsy and sleepy.
How Adenosine Induces Sleep?
- Your brain has receptors, or tissue regions, where adenosine attaches. Your brain neuron cells detect the presence of adenosine molecules once they bind to the receptors.
- The higher the number of receptors attached to adenosine, the more the drowsiness.
How Coffee Improves Alertness?
- Adenosine and caffeine in coffee have similar chemical structures. So caffeine can attach to adenosine receptors, in place of adenosine molecules.
- As more receptors bind to caffeine, fewer numbers are available for adenosine to attach to.
- If adenosine receptors are attached to caffeine and not adenosine, your brain neurons think that your body does not need rest because they cannot find enough adenosine.
- Your neurons stay active, your drowsiness drops, and you feel fresh, after drinking coffee.
How Does The Effect of Coffee Wear Off?
- It takes an hour for blood caffeine levels to reach their peak after you drink coffee.
- Your liver metabolises caffeine (converts it into inactive chemicals), clearing it from the bloodstream. This process takes time as the half-life of caffeine is about 5 hours in the body.
- The caffeine molecules attached to your brain receptors start detaching into your blood as the blood caffeine levels drop.
- After about six hours, blood caffeine levels are down noticeably and many adenosine receptors are free to attach to adenosine once again.
- In nine to ten hours, caffeine is nearly eliminated from the bloodstream.
- By then, more ATP is burned in your body and the adenosine levels increase even more. As a result, you feel sleepier than before drinking coffee.
Tea also has caffeine, but it is about one-fourth of the coffee contents.
The freshness from tea or coffee is temporary and borrowed from the future. If your deadline is long-term, don’t use caffeine to get energy. But if you need to be attentive over a short term, such as for an upcoming presentation or an examination, tea or coffee will be helpful.
Caffeine Tolerance, Dependence, and Addiction
If you drink coffee over a long period, your body as well as your brain adapt to caffeine.
- Tolerance: Your brain develops more adenosine receptors. There are more receptors left for adenosine to attach to even after drinking the same amount of coffee as before and you don’t get earlier freshness and alertness. You have developed caffeine tolerance by needing more coffee to get the same effect.
- Dependence: The body (liver) starts metabolising caffeine faster, removing it from the bloodstream quicker. The drowsiness and fatigue start returning more quickly. You may develop dependence and start drinking coffee more frequently.
- Addiction: The next stage is coffee addiction, where you are unable to cut down on your consumption, even if you want to. Don’t let it get there.
Read this to know the difference between tolerance, dependence and addiction.
More Points to Remember
- Coffee is a diuretic—you end up passing more urine after drinking coffee. This water loss reduces blood pressure. The heart has to beat more rapidly to maintain blood flow leading to tiredness.
- A 250-millilitre or 8-ounce cup of coffee has 80 mg of caffeine. You should not exceed 400 mg of caffeine a day.
- Specific life stages such as pregnancy have separate recommendations. Follow them!
- Have your last cup of coffee ten hours, or at least six hours, before your normal sleep time since it takes ten hours for caffeine to completely clear from your system. Else, you will get disturbed sleep.
This information is from my upcoming book to be published by Macmillan Publishers in Nov 2023. It discusses twenty superfoods, their nutrients, health benefits, recommended amounts and excess levels. It also covers how to select and store and who should avoid them.
The superfoods: Tomatoes, carrots, spinach, beetroot, coconut, capsicum (Shimla mirch), drumsticks, pineapples, papaya, amla (Indian gooseberry), jamun (Java plum), turmeric, garlic, ginger, cinnamon, flax seeds, aloe vera, green tea, asafoetida (hing), and sabja (sweet basil seeds).
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?
- SleepScoreLabs: What Is Adenosine & How Does It Affect Sleep?
- On this Website: 14 signs of sleep deprivation that you may miss
- On this Website: How Much Tea or Coffee is OK in a Day?
First published on: 24th December 2021
Image credit: Mikhail Nilov on Pexels
Last Updated on: 23rd May 2023