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Feeling jittery after just one cup of joe? You could be showing your age. Helen Coffey asks the experts if intolerance is inevitable, and whether there’s anything we can do to get our fix elsewhere
Monday 24 November 2025 06:00 GMTComments
open image in galleryAlmost overnight, this friendly pick-me-up seems to have become a nemesis (Getty)
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Ah, coffee. It’s such an accepted vice these days, it’s even spawned its very own “live, laugh, love”-style culture, complete with cringe-making merch (T-shirts reading: “Just give me coffee and no one gets hurt!”; mugs with slogans like: “First I drink the Coffee, then I do the Things!” – you get the picture).
While I’ve never gone so far as to partake in the caffeine equivalent of an “It’s wine o’clock somewhere!” bit of tat, coffee has, for me, always remained steadfast as one of the low-key joys that make daily life worth living.
But suddenly, almost overnight, this friendly pick-me-up seems to have become my nemesis. More than a cup a day (and even that is sometimes a bridge too far) leaves me jittery and anxious, with a stomach tied in the kind of knots I’d normally associate with exam-taking or waiting for a handsome man to message after a first date. It was such an unfamiliar feeling that, at first, I couldn’t for the life of me work out what was going on. Maybe it was the perimenopause, blamed for seemingly everything past the age of 35? Maybe work stress? Maybe the general melee of war, Trump, and an upsurge in far-right rhetoric taking hold across the nation?
“Have you considered that you might be intolerant to caffeine?” a more level-headed acquaintance proposed instead. This theory, while reasonable, seemed grossly unfair; why would my body, after 38 years on this planet, suddenly turn on me? Am I just a weakling, or is this yet another of the garbage effects that come with ageing?
Possibly both. Just as not all coffee is created equal – there are different strengths depending on brand or coffee shop. Ground coffee packs more of a punch than instant – tolerance differs from human to human too. This is based on genetics, medicines, body composition, hormones, sleep and lifestyle factors like smoking and diet. Hence why “the same coffee can feel fine for one person and too stimulating for another”, explains Emily English, a nutritionist and bestselling author of So Good and Live to Eat.
Caffeine is absorbed quickly, within about an hour of consumption, and reaches peak levels in the blood after around 30 to 60 minutes. Its half-life – the time it takes for the amount of a substance in your body to drop by half – usually ranges from around three to seven hours in healthy humans. But it can be as high as 9.5; factors like age, genetics, liver function, medications and hormonal status all influence this half-life time. It’s why “a late afternoon coffee can still disturb sleep”, according to English: if you drink a coffee with 200mg caffeine at 3pm, there’ll still be about 100mg left by 8pm, 50mg by 1am and 25mg at 6am the next morning.
The University of Bath carried out research investigating the effects of coffee following a night of poor sleep, looking at how it disrupts blood sugar levels and impacts metabolism. Age didn’t appear to be a huge factor, but some people have a single mutation in one of the genes involved in caffeine metabolism that could influence how long caffeine stays in one’s system.
open image in galleryNot all coffee is created equal – there are different strengths depending on brand or coffee shop (PA)“CYP1A2 is the main enzyme responsible for caffeine clearance that results in ‘fast’ and ‘slow’ metaboliser categories,” lead researcher Harry Smith told the BBC. A mutation “could be why some people are able to have more than five cups without consequence whereas others can only manage one per day”.
But ageing also has tangible physical impacts when it comes to coffee, according to the experts. “Many people do become more sensitive to caffeine as they get older,” says Nichola Ludlam-Raine, a registered dietitian and spokesperson for the British Dietetic Association (BDA). This, she tells me, is because our metabolism tends to slow down with age. Caffeine is metabolised in the liver; there are fewer enzymes as we get older, and the liver enzymes that process caffeine (mainly CYP1A2) can become less active and therefore less efficient. “As a result, caffeine stays in the body for longer,” she adds.
A slower clearance rate could create the unpleasant sensations I’ve been noticing, because “it means the same amount of coffee that someone has been habitually drinking would have an amplified effect”, as Dr Elizabeth Ko and Dr Eve Glazier wrote for UCLA Health. “This can cause unpleasant symptoms such as anxiety, irritability, jumpiness, difficulty with sleep, sleeplessness, and the ‘racy’ feeling.” Ie: if my body hasn’t cleared the caffeine from my first coffee out of my system as quickly as it used to, and I’m still stacking a second or third cup of coffee on top, the physical effects are inevitably going to become more pronounced as the caffeine builds up.
Nichola Ludlam-Raine, British Dietetic AssociationMany people do become more sensitive to caffeine as they get older
The studies that most conclusively show increased sensitivity as we age are linked to people in their mid-sixties and older. One study found that coffee drinkers aged between 65 and 70 took 33 per cent longer to metabolise than their younger counterparts. But increased sensitivity could potentially hit at an earlier age, according to James A Betts, a professor of metabolic physiology at the University of Bath’s Centre for Nutrition, Exercise and Metabolism.
“Most likely the timing and magnitude of the changing effects of caffeine with age will vary for us all – as with most aspects of ageing, our body systems can mature at different rates for different organs,” he says. “Some of that may be innate differences in how quickly we age but it often also depends on how well we look after our bodies.”
Ludlam-Raine agrees that it’s very individual, but says that many people notice this change from their forties onwards. Hormonal changes can make a “big difference”, it turns out. Oestrogen can slow the metabolism of caffeine, so during times of fluctuating hormones such as perimenopause or when taking oral contraceptives, caffeine may linger in the body for longer, explains Ludlam-Raine. “This can increase the likelihood of side effects such as anxiety, palpitations, or sleep issues.”
open image in gallerySwitching to a lower caffeine drink like chicory coffee can help if you're sensitive to its effects (Getty/iStock)My big question is, can this increased caffeine sensitivity be reversed? The short answer is: not really. “It’s largely down to genetics, age and hormonal changes,” says Ludlam-Raine. However, you can reduce symptoms by lowering your overall intake gradually, spacing out your caffeine doses and avoiding it later in the day (after 2pm is a no-no for most of us). Staying hydrated, eating regular meals and getting more sleep can also help reduce caffeine’s more “jittery” effects.
And there are things java-philes can do to get their fix. Swapping regular coffee for decaf or half-caf coffee (a mix of regular and decaf) can help smooth the transition, as can making sure you eat a protein and fibre-rich breakfast and drinking a glass of water before your first coffee to steady blood sugar and stay hydrated.
As much as I hate to suddenly hate to be one of those people, I think it’s time to accept that my three-cup-a-day habit is over. Either that or lean in and buy myself a “Just give me chicory coffee and no one gets hurt!” mug.
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