Why does coffee keep you awake?

A glug of strong coffee can give you kick-start out of morning grogginess, or it might help you to keep going if you have to work late into the night.

If you are sensitive to its effects, drinking too much coffee during the day might make it hard to get to sleep at night.

Most of us are aware that the magic jolting ingredient in coffee is caffeine, but how does it make us so wakeful?

It appears that one of the key molecules involved in this effect is adenosine, a biochemical that occurs naturally in your body.

When you are headed for slumber, levels of adenosine rise and bind to specific receptors in the brain, effectively quietening down activity in preparation for sleep. When it’s time to wake, levels of adenosine fall and the brakes are released.

So where does caffeine come in? Chemically caffeine is similar to adenosine and, when you drink a caffeine-rich beverage such as strong coffee, it’s thought to bind to a type of receptor that is usually triggered by adenosine.

By hogging this receptor, caffeine blocks the usual actions of adenosine, so it’s as if levels of adenosine are low, and your brain is wakeful.

If you take enough caffeine on board, it is also linked with releasing adrenaline, which puts your body on higher alert, and increased levels of dopamine, a brain chemical associated with pleasure.

But it’s not without a downside. If you frequently drink coffee, you could experience withdrawal symptoms when you miss your “fix”. So easy does it.