Hi Hazel, so I've been told that you're not supposed to have coffee past 12pm because of

a tough life and how it'll affect your sleep.

But I'm just wondering for somebody who doesn't have to new and work out, is it okay to

drink coffee before that if you're going to be burning off that energy will affect

the half life.

Thank you.

This is a great question and actually I didn't know the answer myself so I'm really glad

that you asked.

There are a lot of papers on the effects of caffeine on exercise but not many the other

way around.

Caffeine has some pretty powerful effects when it comes to mental and physical performance

but the timing and the dose does matter.

So first of all before we jump into the question how does caffeine work?

So it's a cycle act of stimulant and it works through a variety of mechanisms but mainly

through its effects on adenosine.

So adenosine accumulates across the day as we're awake the more we have the sleepier we

feel.

Then caffeine comes in and acts by preventing adenosine binding to its receptor so essentially

it's elbowing caffeine out of the way and blocking it from doing this job.

So this increases alertness which of course can be a positive thing depending on the time

of the day but it can also have a knock on effect your sleep later that night.

So the half time which is the time taken to eliminate half the caffeine from your body varies

...