While a moderate flat white habit is nothing to be worried by, persistently going hard on the java can prove problematic. Here, WH speaks to the experts about what happens in your body, when you mainline caffeine.
What happens after my first cup of coffee?
A thirst for Nero’s finest is usually the result of a few things – from a late bedtime to a longstanding habit. But caving to your craving is no bad thing, particularly as that first cup is likely to perk you up. ‘Caffeine mainly works by plugging the adenosine receptors in your brain,’ explains GP Dr Serena Rakha.
‘Caffeine and adenosine (a compound that usually promotes sleepiness when it hits the receptors) are similar in structure, so caffeine can bind to adenosine receptors, like different keys fitting the same lock, and cause stimulation across the brain.’ After that first coffee or two, this manifests as you feeling alert, with increased concentration to boot.
And my fourth?
Blocking some of these receptors is all good, to an extent, but sipping on four and a half cups of coffee (around 450mg of caffeine) per day can block up to 50% of them. ‘This allows stimulating neurochemicals, such as dopamine, to flood your system,’ says Dr Rakha.
‘When your body catches on, it responds by churning out more adenosine receptors in an attempt to restore equilibrium.’
The upshot? Adenosinestarts binding to the free receptors, which slows down neural activity in the brain (winding down for sleep) –thus, your energy begins to wear thin.
The obvious solution is, well, even more coffee. But as well as blocking sleep-promoting adenosine (so you struggle to nod off hours after your last espresso), caffeine also triggers the release of adrenaline, the-called fight-or-flight hormone, says Dr Rakha.
This rushes through your body, giving you the power to blast through that session on your homerower – at higher doses, though, I'll leave you tense and anxious, and it contributes to the classic ‘coffee jitters’.
So potent are the effects that caffeine-induced anxiety disorder is recognised by the American Psychiatric Association.
So how much coffee is okay?
While the European Food Safety Authority has determined that 400mg of caffeine per day – around four cups of coffee – is fine for most adults, what works for you may be different. ‘There’s also some evidence that caffeine ingestion can increase your circulating stress hormone cortisol,’ says dietitian Sophie Medlin.
‘Cortisol levels peak in the morning, which helps you get up and get on with your day, so if you want to optimise what your Americano is doing for you, you might want to delay it until mid-morning, when your cortisol levels start dropping.’
Otherwise, think about when you might need it most – a recent review concluded that caffeine was an effective workout performance enhancer, particularly for aerobic exercise.
And how do I cut back on coffee, if I need to?
If you want to wind down your dependence, try eliminating one caffeinated beverage at
‘If you experience headache, that’s your previously caffeine-tightened blood vessels widening, creating pressure-like tension in your brain,’ explains Dr Rakha – pop a painkiller if you need to.
‘Often, it’s the ritual of making coffee and sitting down with it that you really crave,’ says Medlin. ‘If you’re trying to reduce your caffeine intake, use that time to brew caffeine-free rooibos instead.’
Still fatigued? Get moving: 10 minutes of climbing stairs will boost your energy as much as an espresso, while the endorphin rush will drown out irritability. Step to it.
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