Drinking coffee before going to sleep or taking a nap can seem counterintuitive. Conventional wisdom dictates that caffeine interferes with sleep. And the belief that drinking coffee or tea before bed affects sleep is so widespread that hundreds of scientists have embarked on a mission to find out if this really is so. Surprisingly, many studies have ended up indicating just the opposite: that having a cup of coffee just before bed does not affect sleep and instead increases your energy level upon waking.
This practice has ended up being called in the Anglo-Saxon world as coffee nap, or coffee nap. And there is a whole science behind its benefits and operation.
The studies. Some research like this one from Loughborough University found that when participants drank coffee and quickly took a short 15-minute nap, they then made fewer errors in a driving simulator than when they were given just coffee or just napped. Another Japanese study suggests that people who drank caffeine before their naps and then took memory tests performed better than the rest. They also said they felt less tired.
How does caffeine affect you? But to understand what a coffee nap does to your body, you first need to know how caffeine affects your brain. When you drink a cup of coffee, the caffeine is absorbed through the small intestine and into the bloodstream and then into the brain. There, it settles into receptors that are busy with adenosine, the brain activity molecule that when built up in large amounts makes you feel tired and sleepy.
However, with caffeine blocking the receptors, he can’t do it. “It’s like putting a block of wood under one of the brain’s brake pedals,” Stephen R. Braun explained in the book Buzz: The Science and Lore of Alcohol and Caffeine.
Then? Caffeine does not block all adenosine receptors, rather it competes with it. And this is where the key is. Sleeping removes adenosine from the brain, and if you sleep for more than 15 or 20 minutes, your brain is likely to enter deep stages of sleep that are harder to recover from (which is why we sometimes wake up tired from naps). But if they are short they do not lead to the so-called “sleep inertia”. And most importantly, it takes around 20 minutes for caffeine to reach the brain.
That is, if you take a 20-minute nap after your coffee, you will reduce adenosine levels just in time for the caffeine to kick in. Caffeine will have less adenosine to compete with and will therefore be even more effective at keeping you energized.
How to do it? Most experts recommend consuming caffeine just before falling asleep for approximately 15 to 20 minutes. And the time of day can also be important. One study found that those who consumed 400 mg of caffeine, the equivalent of four cups of coffee, six, three, or zero hours before bedtime experienced sleep disturbances. That indicates that it is best to do it more than six hours before bedtime. And the amount consumed also affects the effectiveness. Most research suggests that 200mg of caffeine, about two cups of coffee, is recommended.
Why does coffee sometimes make you sleepy? Have you ever felt that coffee tires you, and you are not wrong. First of all, it must be mentioned that coffee is diuretic. With 4 to 5 cups of coffee, it’s normal to use the bathroom more often, resulting in dehydration, dizziness, dry mouth, and lack of sweating. And all these factors lead you to feel fatigued and sleepy throughout the day. On the other hand, if you consume it with sugar, sweetener or honey, it leads to a drop in glucose, a source of energy. People with high blood sugar levels feel tired.
Among other reasons, it could even be the mold found in coffee beans: mycotoxins are the causes of chronic fatigue. And finally, there is stress. Several studies indicate that caffeine doubles the flow of epinephrine and cortisol, even if the person does not consume coffee regularly. And stress causes tiredness.
Less than nicotine or alcohol. Still, a cup of coffee doesn’t hurt your sleep as much as a cigarette before bed. So says another study from Harvard University published in the journal Sleep. In this case, caffeine consumption in the hours before bedtime had no impact on how long it took subjects to fall asleep, how long they slept, or whether they woke up during the night.
In contrast, those who enjoy a glass of wine with dinner or drink alcohol before going to bed have “a small but statistically significant reduction” in sleep efficiency and fragmented sleep. Mind you, the biggest bad thing was nicotine: smoking within four hours of bedtime was associated with sleeping just over 42 minutes less, on average, and they had lower sleep efficiency.