I know that most people are accustomed to have some coffee right after getting out of bed. I used to schedule my coffee filter instead of an alarm, just so I can wake up to the smell of freshly brewed coffee. Nice as it may sound, biologically it was not such a great idea. I was used to preparing an 8-cup filter, drinking it steadily from morning until 6pm. Once I’ve learned a few things, I’ve replaced the coffee filter machine with an espresso one and switched the intake to 3-4 espressos. That’s more or less the same amount of caffeine, but brings me closer to what would be “the best time to drink coffee“.
The natural rhythm of our body
For a regular person working during the day and going to bed at night, the body follows its “default” settings. I am talking about the circadian rhythm. Cortisol, the so-called stress hormone, naturally peaks between 8-9 am, 12-1pm and 5:30-6:30pm. Instead of giving you exact hours, let’s say it reaches its peak level about 30-45 minutes after you wake up and first round should last about an hour. Lower levels of cortisol are 3-4 hours after you wake up.
Cortisol, connected to fight or flight response, raises alertness and focus. However, in the morning, it rises just to wake you up. It has also other benefits such as regulating your metabolism, blood pressure and helps with tissue healing. For nightshift workers, the circadian rhythm tends to change and cortisol rises around the time they wake up to go to work. Constant levels of high cortisol (chronic stress) obviously damage the immune system, so we don’t want to enhance it.
Here’s the bad news: cortisol also spikes when sitting inside all day (sounds like work from home, right?), eating inflammatory foods (processed meat, processed grains, fried food, sodas) or not consuming enough carbohydrates.
Caffeine rises cortisol. If you drink coffee when cortisol is already high, you’ll get some morning anxiety and possibly none of the benefits. Caffeine’s effect last between 1 to 6 hours, but we’ll get to that. For regular coffee drinkers, the effect on cortisol may not be that high. They can also feel more energised if they delay a bit the morning coffee.
Why do you feel tired or sleepy?
Feeling sleepy is the effect of adenosine. It’s a molecule that inhibits neural activity when detected. We could say it signals fatigue to our brain. It’s low in the morning and continuously accumulates during the day, closely tied to digestion. The brain detects these levels through specific receptors. Receptors are nothing but proteins in the membrane of a brain cell. When receptors detect a neurochemical they can read, the neurons trigger a specific response. Either they stop the signal (the trigger) or pass it forward to the next cell, or diminish it. Receptors have a critical role for learning and memory, but we will not get into details.
Caffeine blocks the adenosine receptors or rather it binds to the same receptors. It does not leave any room for adenosine to be detected. That doesn’t mean that adenosine doesn’t keep accumulating, it obviously does. The brain just isn’t aware of it. That is until the caffeine effect wears out and … well, you’ve actually felt this. Did it ever happen to you to “suddenly” feel sleepy, like you can barely keep your eyes open? That “I need to sleep NOW” sensation. That’s the accumulated fatigue that’s not blocked anymore. As a consequence, the brain, reading the high levels of adenosine, sends you the shutdown command.
Adenosine washes away when you sleep. If you don’t sleep enough, adenosine is still there and you will feel tired. As a result, you drink coffee to be able to cope with the day and more adenosine accumulates on top of the one that didn’t wear out.
So when is the best time to drink coffee?
The best time to drink coffee is between 9:30-11:30 am or as a rule of thumb, ideally 3-4 hours after you wake up, but not less than 2 hours. The latest you should be drinking coffee is 6 hours before going to bed, if you don’t want it to impact your sleep.
The caffeine in a cup is fully absorbed in the bloodstream in about 30 minutes, but its first effects are noticed after the first 10 minutes. The body needs 5 hours to metabolize half of the caffeine in one cup and 10 hours to wear it out completely. So if you go to bed at 11pm or midnight, you should have the last cup by 4pm the latest. That way, your body has almost eliminated it, by the time you fall asleep.
The maximum intake of caffeine/day should be 300-400mg. Maximum (!), not “recommended” intake. A cup of brewed coffee (240ml) can contain up to 100mg of caffeine. AeroPress has a lower concentration. An espresso of 30ml has roughly 60+mg.
Now you know 😊
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