Why coffee helps you stay awake — what is adenosine?

For everything that is produced, there is always a resultant waste.

The effect of caffeine on sleep was a discussion I had with King over dinner one evening.

While we’ve all heard of the role of melatonin on sleepiness in our general studies, few have really dived deep into what our brain generates to keep us awake and why we require sleep.

“I was reading up on brain chemistry this afternoon and I came across something known as ATP,” he said, slurping up a spoonful of soup. “What is known as a universal biochemical unit of currency of intracellular energy transfer.”

Naturally, who wouldn’t be perplexed at being thrown into a discussion about brain matter while enjoying your meal. Nevertheless, I humoured him and discussed what I had known about caffeine and its effects on sleep.

Like most people, my knowledge of the effects of caffeine was shallow.

I had heard that caffeine prevents the brain from producing adequate levels of melatonin to induce sleepiness. That was why drinking coffee made you less eager to head to bed. However, as your body builds up a tolerance for caffeine, you would need more and more of it to stay awake for longer. It’s why there are melatonin pills for sale at the pharmacy!

Turns out, I was wrong (is this is becoming a habit or what).

What is Adenosine?

Adenosine triphosphate (or ATP) is an organic compound that provides energy to drive many processes in living cells, such as nerve impulses, chemical synthesis, and more.

It is found in all known forms of life. Often referred to as the “molecular unit of currency” of intracellular energy transfer, when consumed in metabolic processes, it converts to either adenosine diphosphate or adenosine monophosphate or degraded to adenosine.

Adenosine and its various forms also come in the form of drugs. Singular adenosine is often found in drugs used to block faulty circuitry in the heart. Meanwhile, ATP is used to prevent changes in energy metabolism that causes weight loss

As the currency of energy exchange, ATP is constantly formed and broken down as part of our body’s biological reactions. It is central to the health and growth of all life, as it is involved in helping cells transfer energy from one to another, enabling organisms to grow and reproduce.

When we are awake, the neurons and glial cells in our brains utilise huge amounts of ATP to produce the right chemical reactions throughout the day. Adenosine levels increase as a bi-product and impose “sleep pressure” on our brains.

Adenosine, as it accumulates in our brain, progressively binds to receptor sites in the brain. One of the triggering effects of this binding process is the urge to sleep after 12-16 hours. As this process escalates, ATP depletes. Once we sleep, however, ATP gets restored and an enzyme called adenosine deaminase (or ADA) then metabolises adenosines. When we wake up, the cycle continues again.

Caffeine Is Similar To Adenosines

Have you ever experienced a crash in energy levels after drinking too much coffee? That moment when exhaustion absolutely terrorises your body, feeling like you got hit by a truck and you’re suddenly ready to pass out?

Caffeine is a direct competitor of adenosines for your brain’s receptor sites.

Unlike adenosine, however, it only has a half-life of 5-7 hours during which it occupies these receptor sites and prevents the effects of adenosine build-up. Essentially, adenosine continues to build up but because they do not bind themselves to the brain’s receptor sites, you do not progressively get tired.

Once the liver’s enzymes break down caffeine during the 5-7 hour time period, the receptor sites become available again and suddenly they will be overwhelmed by the surge of adenosine suddenly able to bind themselves to them. Hence, the crash.

And so, contrary to belief, perhaps melatonin plays only a little part in the science of sleep.

Rather, it is how much adenosine has bound to receptor sites that give our brain the signal to rest.

Special thanks to my mentor, Mr King TK Chan, for his contributions & teachings.