HARRIET GREEN: I was drinking 10 coffees a day. My sleep was terrible and this one side-effect was driving my husband crazy. This is how I’m taking control over my caffeine addiction – and you can too

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My name is Harriet, and I am a coffee addict. Coffee is the first thing I think of when I wake: fire up the Bialetti moka pot, add a dash of almost-boiling milk and… aaah! Bliss.

But once I start, it’s hard to stop. On a typical day I’ll have five full pots before lunch – the equivalent of ten single espressos. I don’t eat breakfast, so it’s a pure caffeine diet from 7am to past noon. Towards lunchtime, I can feel my stress levels rising. I’m jumpy, a little snappy, busy, busy, oh, so busy – but do I actually achieve anything?

Emeritus Professor Peter Rogers, a psychologist at the University of Bristol, has done a huge amount of studies over the years on what caffeine does to the body. ‘Our research found non-caffeine consumers don’t perform better on tasks when given caffeine. They feel more wakeful and more anxious, but not more focused.’

Also, my sleep is appalling. Ten espressos! What did I expect?

Recently, I started tracking my sleep with an Oura ring – a smart device that measures your heart rate, temperature and movement. It shows what I already know: my sleep is poor and my nights restless. The cold, hard data is sobering.

Harriet with her morning Joe, 1973

My love of coffee goes back to childhood. My grandmother adored Italy and brewed coffee using the classic Bialetti pot. It’s one of my earliest memories and I’ve always loved the logo: the little moustached man with his finger raised. I’ve had my own Bialetti since I was a student, and bought my latest version – the Venus, in metallic blue – on a recent holiday in Verona.

A hazy photograph from the 1970s shows me, about five years old, sitting at the breakfast table in a quilted dressing gown, clutching a glass mug that’s already drained of liquid. That coffee was probably my second of the day.

I didn’t like the taste so much, then. I would stir in sugar till the grains crunched on the bottom. Every morning I bounced to school, a small girl with a bubble of blonde hair, totally wired.

In the evenings, my parents had dinner parties – 70s maxidresses, boeuf bourguignon and big hair – followed by black espressos from tiny cups and a Bendicks Bittermint on the gold-rimmed saucer. If I was allowed to stay up, I would have a coffee, too. Then off to bed, totally zipped.

Caffeine is the world’s most popular psychoactive drug. It has a long and rich history. One story claims a ninth-century goatherd called Kaldi noticed his goats were more full of energy after eating coffee berries. So he tried some himself. Yemeni Sufis roasted the seeds of the berry to create the drink we recognise today and stay awake during long prayer sessions. The world’s first coffee houses appeared in the 15th century, across the Ottoman Empire. Within 200 years, Europe was buzzing too.

Voltaire was said to drink 40 to 50 cups a day. More recently, Robbie Williams reportedly consumed up to 36 double espressos daily when he checked into rehab in 2007.

Earlier this year, I spent four days at a health spa that provided a barley-coffee substitute. On day two, feeling properly ill – pounding headache and feverish – I took from my suitcase an M&S coffee bag I’d packed just in case, and felt like a sad addict as, in desperation, I tried to brew a cup using tepid water from the bathroom tap.

This, surely, was rock bottom. It was time to cut down – or stop altogether.

My friend Philippa Perry, the psychotherapist and agony aunt, has been decaf for years. ‘Honestly, it’s worse than coming off heroin,’ she says, and she’s not exaggerating: ‘I’ve worked with addicts and that’s what they’ve said.’

I turn to the celebrity acupuncturist Ross Barr, who has described coffee as ‘the energetic equivalent of doing a little bump of cocaine’. Each cup agitates the endocrine system, he tells me, releasing the flight-or-flight hormones adrenaline and cortisol regardless of actual need.

For someone who is already wired, tired or anxious, coffee amplifies that state. ‘It’s throwing powerful oil on the fire of your angst,’ Barr says. At his London clinic, he takes my pulse and treats me with needles. Lying down for 30 minutes gives me time to think. I’ve had two coffees before seeing him – the second one I glugged down in his waiting room. He suggests I stop for the day and, remarkably, I manage without too much trouble. He’s a great listener and I find that talking about my habit is incredibly helpful. As others before me have found, admitting to having a problem makes it easier to tackle.

And yet, and yet…

There’s plenty of research demonstrating the benefits of coffee. Only two months ago, a study by Warwick University showed that coffee drinkers are happier in the first two and a half hours of the day. ‘Caffeine works by blocking adenosine receptors, which can increase dopamine activity in key brain regions,’ explained Professor Anu Realo, ‘an effect linked to improved mood and greater alertness.’

Meanwhile Professor Tim Spector, the epidemiologist and gut expert, extolled the virtues of coffee on his podcast, specifically its fibre content and high levels of polyphenols (‘like rocket fuel for your gut microbes’). They can have, he said, ‘amazing protective effects on the rest of the body, particularly our hearts.’ I should add that Spector says there’s a point where enough becomes too much. ‘Health data shows that if you have between one and five cups of coffee a day, it’s healthy. As soon as you get to six or more, you seem to lose that benefit.’

But here’s the problem: with so many variables – the bean, processing and brewing techniques, water content – it’s hard to say exactly how much caffeine is in any given cup.

One day, attempting to be scientific, I measured my intake. For years, I’ve brewed Lavazza Rossa, a blend that’s widely available in supermarkets. And it turns out that I use 16g in each moka-pot brew, which means 180mg to 205mg of caffeine per cup. Most mornings, I drink five of these. That’s 900mg to 1,025mg of caffeine every day. The American Food and Drug Administration estimates that the safe limit is approximately 400mg.

James Hoffman has a successful YouTube channel (more than two million subscribers) dedicated to coffee. His book, The World Atlas Of Coffee, is in its third edition. He agreed with my calculations, adding that the high figure is partly because of the beans that go into my preferred blend.

‘Lavazza Rossa has some robusta beans in it [about 30 per cent], and robusta has about twice the caffeine content of arabica. So you’re starting with a lot more caffeine to begin with. Sixteen grams of robusta – it’s like drinking 24g of pure arabica.’

Hoffman loves coffee, but he’s clear-eyed about how much is too much: ‘My line on caffeine is: it is the world’s most popular psychoactive drug, yet nobody has any idea how much they’re taking. With alcohol, for example, everything’s listed. Caffeine? Not a clue! If people knew how much they were consuming, they might drink less.’

Hoffman stops drinking coffee by 2pm. ‘Sleep is really important to me, so that’s a hard limit on my caffeine consumption,’ he explains. ‘I would generally not exceed 330mg to 350mg a day.’

He suggests I switch to an arabica blend. ‘Right now, it’s a great time to be a coffee consumer in the UK; you have so much choice. Have a look, initially, for a pure arabica.’ He warns me that I’ll notice a difference in taste, and advises I shouldn’t aim to cut down too fast, say from 1,000mg a day to 200mg. ‘You may have a day or two where that doesn’t feel great.’

I could also experiment with different coffees at different times of day, Hoffman suggests. Sometimes he has a decaf in the afternoon, ‘when it’s dark outside, and I want that coffeeness, but I also want to sleep later on’. Decaf used to be a poor alternative, but no longer, he says. ‘And there are lots of options out there for half-caf.’

Strangely, it’s not my mood that finally encourages me to cut down. For some years, I’ve been going to the loo many times a night – a common symptom of the perimenopause/menopause – and it’s been getting worse, ruining my sleep and driving my husband crazy. Last month, as I was researching this article, I got a urinary tract infection. There are strong links between coffee and bladder irritation. I cut back, and on the days I drank less coffee – as the Oura ring confirmed – my nocturnal loo trips fell sharply.

I’m not ready to give up coffee completely. I’ll cut down to two cups before noon and follow Hoffman’s suggestions for alternative blends and an excellent decaf. My sleep will be better – I really hope – my bladder calmer and my daytimes less jittery.

But ultimately, I agree with the great Jerry Seinfeld. ‘I think coffee is the most important part of a human’s life,’ he once joked. ‘When you get to the end of this life, before you move on to whatever is next, I think it’s quite possible your last thought will be, “That was good coffee!”’