I have a long and deeply passionate love affair with coffee. The smell, the associations, the routine, the taste – I bl**dy love everything about it. In fact, I’ve just bought some stupidly expensive hazelnut flavoured coffee to get a little hit of NYC living down here in sleepy Somerset.

Having suffered from CFS/Fibro for most of my adult life, coffee has been both my nemesis and my salvation. I’ve tried to give it up countless times, even resorting to hypnotherapy (it worked for a month or so), reading books on habit change, trying to moderate my habit, emptying the whole house of it… But there’s a reason it’s the world’s favourite drug. It’s addictive, wonderful, and helps us survive in this hectic, demanding world. Incidentally, I think part of the reason it’s so hard for me to give it up is that it stimulates the release of dopamine, and a widely held theory about the root cause of fibro is that it’s a a dopamine disregulation (ie too little of it).

I’m not about to tell you to kick the habit – that would be hypocritical and impossible!

Instead, let’s learn a little bit more about caffeine and how it works, how it affects your sleep, and most importantly, how and when to have your best cup, making it work for you.

There are two things which trigger your urge to sleep – your circadian rhythm and sleep pressure. Interestingly they are two completely separate entities. So firstly your biological clock (circadian rhythm) operates on a cycle between 24 and 25 hours – if you’re interested it’s 24 hours and 15 to 20 minutes. That biological clock is going to trigger our body to go to sleep to some extent – although the slightly ‘off’ timing does mean that we constantly operate in a very slight state of jet lag. This can’t be affected by caffeine, only by light (which we’ll cover in another post).

Sleep pressure however is affected by coffee. When we wake up after a great night’s sleep and when our body has restored itself, then a chemical messenger called adenosine is very low. During the day this neurotransmitter builds up and up until it hits a certain level in the evening, causing that feeling of sleepiness and sleep pressure, which should (…) send us off to the land of nod.

The interesting thing is that the molecules adenosine and caffeine are very, very similar. So caffeine works by blocking the action of adenosine – it docks into the adenosine receptors instead, a bit like a key in a lock, and prevents the signal from being transmitted to the brain. But… adenosine doesn’t stop being produced, it simply keeps building up outside these receptors, waiting until the caffeine is eventually flushed out in order to take its rightful spot.  

The first thing to realise is that caffeine is not making you feel more refreshed.

It’s just stopping you from getting more and more tired. Secondly, when your liver kicks in and flushes out the caffeine, you will have a huge crash, as the backlog of adenosine will rush in there and trigger that a lot of tired signals. Instead of building up gently, you now have sleep pressure hitting you at full throttle.

How quickly will that caffeine get moved on – in other words, how long until you crash? Caffeine is flushed out through the liver and metabolised (or made inactive) by a specific enzyme. That enzyme works very individually – some of us have a version that gets rid of caffeine pretty quickly and others have a variant that works more slowly. But in general, the average amount of time needed to reduce the stimulant effect of caffeine by half is 6-8hours, ie a loooong time. If you think that caffeine doesn’t affect you, that you have a variant of the gene which means that you can have an espresso at 10pm and still go to bed at 11, don’t be fooled. I often have to explain to my clients that they’re simply so sleep deprived that their brain throws them into sleep, but the caffeine will turn melatonin off and affect their sleep quality.  A latte mid-late afternoon can still interfere with your evening. And remember that it’s not just the caffeine in coffee, we’re talking tea, dark chocolate and energy drinks. Also worth noting that decaf is still 10 to 15% caffeine, so not totally caffeine-free.

What would be the best way to ramp up your energy, yet stay smart about protecting your night’s rest? There seem to be two key times during which we need that extra boost; for mental focus in the morning and to stave off the early afternoon slump. I have a pretty fail-safe strategy for both, but there is a catch.

You absolutely need to try and get out of the habit of drinking coffee first thing in the morning.

If you drink coffee when your cortisol level is high – generally 2 hours from waking – the effects are non-existent and all it does all this does is increase caffeine tolerance. We have all noticed the law of diminishing returns – the more you drink, the less effective it is. 

However if you drink it when cortisol levels are low, then caffeine gently nudges your adrenals into giving you a hit of adrenaline and you will feel more awake and alert. So we’re aiming to time coffee breaks with dips in your natural cortisol level to effectively boost energy. For the average chronotype, those dips occur between the hours of 9.30am and 11.30am, and between 1.30pm and 5.30pm. As per the brilliant book by Michael Breuss (see my recommendation here), there are 4 different chronotypes, and each has a different natural cortisol cycle – the aim of the game is to make it fit with this ‘one-size-fits-all’ modern lifestyle.

So now you’ve had your gorgeous cup of Joe, written that epic presentation and made those tough calls, don’t reach for a second one. Keep going until you’ve had lunch. Your circadian rhythm is going to have a natural dip between 1:30 and 3pm, and you’re going to feel tired – especially if you’ve had a carb-heavy meal. An interesting fact is that caffeine takes roughly 20 minutes to kick in and attach onto your receptors, so the ideal scenario – if you have to have your coffee – is to have a quick shot at 1pm, followed by a power nap of 20 to 30 minutes. You will then have renewed energy from your nap and block adenosine from your receptors. This should make you feel super alert for about 4 hrs, just in time for coming home and winding down. And this way, the buffer is sufficient that you don’t suppress the production of melatonin.  But remember, you will get that backlash of pent up adenosine and will dip sometime around the early evening – hopefully no bad thing unless you have small children demanding to be wrestled with (sounds familiar??).

The worst time to have coffee: within 2 hours of waking & within 6 hours of bedtime.

In summary, my advice is to wait until your cortisol level dips in the am to have your first cup, and to have the last, or second one before 2pm in conjunction with a power nap.