Why Does Coffee Make You Feel More Tired?

Caffeine blocks adenosine receptors, so the sleepiness signal keeps building while it is masked. When the caffeine clears, that accumulated adenosine lands at once, which is why the more coffee you drink, the more tired you can feel. It works like spending energy on credit rather than creating it.

Timing and amount matter more than total cups. Caffeine has a long half-life, so coffee six hours before bed can still disrupt sleep and deepen next-day fatigue. Minors face separate risks: caffeine activates the sympathetic nervous system, raises short-term blood pressure, and stimulates bone resorption.

Caffeine can boost alertness, but it can also overdraw your body's energy like swiping a credit card. When adenosine keeps accumulating and receptors are repeatedly blocked, you fall into "caffeine burnout," where the more coffee you drink, the sleepier you feel. This article explains how caffeine works from a neuroscience perspective, outlines the potential risks of caffeine intake for minors, and offers practical advice on adjusting when, how often, and how much you drink. At the end, Front Street Coffee's brand recommendation information is retained for coffee lovers' reference.

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"Drinking coffee is like swiping a credit card—you're drawing on your body's energy quota in advance, and at some point you'll overdraw."

People's love of coffee may stem from its flavor, or from the fact that its chemical components act on the nervous system, bringing physiological stimulation and sensory pleasure—allowing people, in a world of mental stimulation, to briefly alter their waking state of consciousness and simply and directly shake off low spirits.

Caffeine is a recreational substance accepted by today's society, and there are currently no age restrictions on it. But perhaps one day it will be locked in a back-room cabinet like alcohol and prescription drugs, with minors forbidden from accessing it.

A previous consumer survey in South Korea showed that more and more lower-grade students are buying caffeinated beverages (coffee, energy drinks, etc.) in their spare time, and the higher the caffeine content, the more popular they are with students. Yet we also know that excessive caffeine intake by minors affects their development, and there is currently no law anywhere in the world prohibiting minors from buying caffeinated products.

- Screenshot of a line from the TV drama "Extraordinary Attorney Woo"

Minors are not suited to caffeine intake. One reason is that caffeine can activate the sympathetic nervous system, causing short-term blood pressure increases and raising the risk of hypertension, which is bad for children's cardiovascular development; another reason is that caffeine stimulates osteoclast activity, and long-term intake affects calcium formation in bones, which is bad for children's bone development.

Minors should not consume caffeine over the long term, and the same goes for adults. The latest research suggests that coffee may not only fail to replenish energy, but actually consume it. In other words, if adults consume excessive caffeine over the long term, not only will it fail to refresh them, but they will feel increasingly exhausted.

Just like a credit card, every caffeine intake is equivalent to drawing on your body's quota in advance. If you keep swiping the card and never "repay," you will eventually hit the limit and be unable to continue using it.

Neuroscientist and Stanford University professor Andrew Huberman calls this phenomenon "sleep hunger." The longer this state persists, the more it ultimately leads to a situation where no amount of coffee works—that is, caffeine burnout.

"Isn't caffeine supposed to refresh you? Why does it still make you sleepy?"

Let's first take a brief look at how caffeine makes you briefly alert.

People feel drowsy because the brain secretes a substance called adenosine, which is an inhibitory neurotransmitter. When adenosine binds with another signal substance in the brain that recognizes it specifically—a receptor—people feel sleepy. The more adenosine binds to receptors, the sleepier people become.

When you take a sip of coffee, what happens in your brain is roughly this…

(The pink cushion plays the receptor, the cow cat plays caffeine, the orange cat plays adenosine)

Caffeine can't grab the two of them and make them sway together. All it can do is step in front of the receptor ahead of time and briefly block adenosine from binding to it. The fact that adenosine hasn't bound to the receptor doesn't mean the brain stops secreting adenosine, because the body needs adenosine to help reduce inflammation, regulate heartbeat, promote digestion, and so on.

The human body prefers regular sleep, so the brain releases adenosine according to a 24-hour circadian rhythm. If you force yourself to stay up late, you'll feel even more drowsy, because the brain releases more adenosine than usual to help you fall asleep at your normal time.

The same principle applies to drinking coffee. The more caffeine you take in, the more adenosine there will be, and your body feels hollowed out—your consciousness is awake, but like a soulless shell, your body is extremely exhausted. At this point, continuing to consume caffeine is meaningless. This state is caffeine burnout.

If this state is maintained over the long term, it will eventually cause the body to develop "tolerance," and caffeine will no longer stimulate the nerves. The person will only become more and more tired and more and more drowsy.

"Then how can I avoid caffeine burnout? I still need it to keep going!!"

Adjusting rest times, coffee intake frequency, and intake amount is very important.

The half-life of caffeine is five hours, and it takes ten hours for caffeine to become completely ineffective. This means that drinking a cup of coffee five hours before bed is equivalent to drinking half a cup right before sleep. So in the 5 hours before bed (preferably 10 hours), do not consume caffeine-containing foods (including coffee, cola, tea, chocolate, functional drinks, etc.), which can effectively improve sleep quality.

In general, adenosine needs time to fade in the early morning, so drinking coffee immediately after getting up actually doesn't refresh you; instead, it stimulates more adenosine production, making you feel like you can never fully wake up. The best time to drink coffee is 90 minutes after waking up. This gives adenosine time to fade, and drinking coffee after it has mostly faded can achieve a better refreshing effect.

While coffee makes you focused and excited, it also increases your stress. So when you feel stressed, don't choose to consume caffeine! This will also cause the brain to produce more adenosine to regulate heartbeat and ease emotions.

Coffee is not some miracle cure. When your body feels tired, what it needs is adjusted rest, not tricking yourself by stimulating the central nervous system and overdrafting your capabilities.

As the classic line from old Hong Kong triad movies goes: If you go out into the world, sooner or later you have to pay it back! Everything you overdraft must ultimately be repaid.

Good health is what matters most!

Image source: the internet

The above content is compiled by CoffeeHunters, a coffee news website.