This article Chinese about 1000 words and takes about 2 minutes to read
People often ask why it is useless to drink coffee, or even more sleepy, today to talk about this problem.
How does coffee "refresh"?
There is an energy metabolite called "adenosine", which is responsible for sending signals to the brain that "the body is tired, sleepy, and needs to rest".
Caffeine, on the other hand, competes for adenosine receptors in the brain and prevents adenosine from "talking" to the brain, thus keeping us awake and excited.
Why do people get sleepy after drinking coffee?
In principle, coffee doesn't make you "sleepy." If you finish your coffee and feel sleepy, you can only say that these two things happened one after the other, but there is no causal relationship.
The biggest possibility is that you drink coffee late, your adenosine has spoken to your brain, and coffee can't do anything about it.
As for why some people drink coffee is useless, it may be that they belong to the type of caffeine metabolism or insensitivity to caffeine. It may also be a long-term heavy drink, resulting in a decrease in sensitivity.
How can coffee be more effective?
Drink early
It is useless to drink it after being sleepy to a certain extent, it is best to drink it in advance. For example, if you need to be sober in the morning, drink it in the morning. If you need to wake up in the afternoon, drink at noon.
As a reminder, if you drink coffee after 3 p.m., you may not be able to sleep at night.
(Caffeine in the body about 5-7 hours will be metabolized in half, about 8-10 hours metabolism of 75%, so it is best not to drink coffee within 5 hours before bedtime, of course, everyone's sensitivity depends on your metabolic capacity and the amount of coffee you drink on a daily basis, some people just don't have a problem.) ）
Coffee Nap
If you do feel sleepy but have something to pick up, you can set aside 20 minutes for a Coffee Nap.
This is what scientists have proven to be effective by pouring a cup of coffee and then taking a 15-20 minute nap.
During napping, your adenosine will slowly dissociate from the receptor, and the caffeine that has been waiting on the side can be on top in time to occupy the receptor and prevent adenosine from binding again, which will achieve the purpose of refreshing.
But this nap is best not to exceed 20 minutes, because naps within 20 minutes are easy to wake up, and more than 20 minutes your brain may go deeper into the sleep phase and it takes some time to wake up.
Coffee is not a lifesaver
Coffee can't cope with all problems, if you are chronically sleep deprived, resulting in a sluggish response, coffee will not be able to manage...
Sleep well with coffee!
Although coffee can make people more sober, there are also studies that show that the improvement in reaction time and judgment is not much, and even college students who drink alcohol and coffee regularly are more likely to be in car accidents.
Can't drink too much
The current conclusion is that it is safe for adults to consume no more than 400 mg of caffeine per day.
Excessive coffee drinking can not only easily lead to a decrease in sensitivity to caffeine, but also may lead to symptoms such as heart rate and breathing, insomnia, irritability, headache, stomach discomfort, or increase anxiety.
There are also studies that suggest that heavy intake of caffeine may accelerate calcium loss, but the relationship between this loss and osteoporosis is unclear.
Resources:
[1] Juliano L M, Griffiths R R. A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features[J]. Psychopharmacology, 2004, 176(1):1-29.
[2] Dam, Rob M et al. “Coffee, Caffeine, and Health.” The New England journal of medicine vol. 383,4 (2020): 369-378.