Effects of Caffeine on the Body

effects of caffeine on the body and sleep

Caffeine Consumption & Your Body

  • The effects of caffeine can take over 24 hours to fully leave the system.
  • Caffeine keeps us feeling awake by suppressing adenosine, the chemical in our brain telling us to sleep.
  • A cup of decaf coffee still contains 15 to 30% of the caffeine a regular coffee provides.
  • Coffee, chocolate, black and green tea, energy drinks, and soft drinks all contain caffeine.

Caffeine is the most used and abused psychoactive stimulant in the world- second most traded commodity on the planet after oil. It has become the life-blood of modern society. For many, it’s what helps fuel us for the long day ahead.

But how exactly does caffeine affect the body and allow us to stay awake longer and later into the night?

Effects of Caffeine on Sleep Pressure

This feeling of tiredness, when we just can’t seem to keep our eyelids from drooping down, is caused by something called sleep pressure. Just as its name suggests, sleep pressure is the compulsion to sleep, which is caused by a naturally occurring chemical in the body called adenosine.

The chemical builds up in the brain, and continues to do so with every moment we are awake. The longer a person stays awake, the more build-up of adenosine there is in the brain. This pressure it what helps to keep our sleep-wake cycle, or circadian rhythm, in check.

It is this chemical adenosine that caffeine directly affects.

For adenosine to latch on to the brain, and begin pressuring the body to sleep, it needs a landing site. Imagine for a moment that our brain is a giant roof with a large H helicopter pad- this is where adenosine will land and start creating sleep pressure.

Caffeine effectively wipes away the big red H landing, blocking the adenosine from landing upon the brain, and cutting off the signals that tell the brain it is time to sleep. This, in turn, helps the mind feel more awake.

However, the helicopter that is adenosine is still hovering above the site. It is gathering momentum and waiting for the moment to land to put pressure on the brain to sleep.

The Half-Life of Caffeine

The effects of caffeine typically peak thirty minutes after it has been consumed- it is relatively fast-acting. People love it for this reason- however, many do not know just how long caffeine stays in the system and affects the body.

The term ‘half-life’ is used to describe a substance’s efficiency, and length of time it takes for the body to dispel 50% of the substance’s concentration. Caffeine’s half-life is approximately 5 to 7 hours. After that time, there is still 50% of this stimulant active and circulating through the brain. All together, caffeine can linger in your system for over 24 hours.

Those that enjoy a nice cup of coffee as an after-dinner dessert at 7:30 pm will still have the caffeine circulating in their system by 1:30 am. The body is only halfway done flushing the effects of this stimulant from the body, drastically plummeting the night’s quality of sleep as a result.

Caffeine is the leading contender for causing sleepless nights in people, disguising itself as insomnia. With such a long half life, many people don’t make the connection between bad sleep, and the coffee they consumed mid-afternoon.

You may think that drinking decaffeinated coffee would nip this problem in the bud. Contrary to popular belief, decaffeinated does not actually mean zero caffeine. A cup of decaf coffee can contain between 15 to 30% of the caffeine a regular cup of coffee provides.

So how does the body dispel caffeine once it’s in the system? This responsibility falls to enzymes housed within the liver, which gradually degrade the effects of the stimulant from the bloodstream over time.

How capable the liver’s enzymes are at cleansing the bloodstream has to do mostly with genetics and age. Some are hereditarily better at flushing caffeine from the system than others. It is also easier for a younger person to metabolize this substance over those that are older.

Effects of the Dreaded Caffeine Crash

After consuming that cup of coffee, we eagerly await for the effects to wash over us and dispel feelings of fatigue and exhaustion. Once that happens, we promptly continue with our day and forget about that sleep pressure and buildup of adenosine happening in the brain.

But that adenosine has not forgotten about us.

Caffeine effectively removes the giant landing pad H from the brain for a time. Still, the adenosine is just waiting to swoop in once that landing site is cleared of caffeine. And that sleep pressure continues to build up, compounding in force even if we don’t feel it yet.

It is this buildup and subsequent release which causes the dreaded crash of energy. Once the liver has done its job of clearing away caffeine and unblocking the big H landing pad on our brain, the magnified sleep pressure overwhelms the site, creating a riptide of adenosine.

At this point, staying awake is going to be exceptionally hard to do.

Resetting Your Sleep Pressure

Once we sleep, the brain sweeps away the buildup of adenosine. When we wake in the morning, the accumulation of sleep pressure starts anew.

However, if you are regularly not achieving the recommended 8 hours of sleep, the full amount of adenosine will not be removed from the brain. Leftover adenosine causes us to consume more caffeine in the morning, starting the process all over again. Therefore if you are looking to cut down on your caffeine intake, achieving a higher quality and quantity of sleep can do the trick.

For tips on improving sleep, check out our Top ten techniques for falling asleep faster, or how about introducing yoga into your bedtime routine.