Minute by minute, this is exactly what your daily cup of coffee is doing to your brain, gut and heart - as shocking caffeine count in high street drinks is revealed

Britain is a nation fuelled by caffeine - drinking around 95 million cups of coffee every day. And, according to the latest research, we may be consuming far higher doses of the stimulant than we realise.A medium cappuccino from high street favourite Costa's, for instance, contains the equivalent of four Red Bull cans worth of caffeine, as revealed by experts at Which? this week.That's 325mg of the energiser, and almost the entirety of the safe daily limit of 400mg, or five coffee cups. Meanwhile Pret A Manger's espresso was found to be four times stronger than Starbucks' version, containing 180mg of caffeine - nearly half of your total daily recommended intake. Yet, amid the various health warnings about the harms of the stimulant, some studies suggest it may in fact bring benefits. One 2026 study found those who drink five or more cups a day were 47 per cent less likely to develop liver cancer, while other research has found coffee lovers have a lower risk of heart disease thanks to its anti-inflammatory compounds, known as polyphenols. So what exactly happens following that very first sip? Here, experts reveal the body-wide impact of caffeine throughout the day... Once you've had a morning cup of coffee, you'll find yourself wanting more throughout the day, experts say The first sip: The immediate 'buzz'Caffeine's effects depend on how much you consume – but can be felt almost instantly from the very first sip.'Caffeine consumed in coffee is a key part of daily life for millions of people,' Dr Gregory Marcus, chief of cardiology for research at the University of California said. 'For most adults, intake of up to 400mg a day - around five cups - without added sugar is safe and does not increase cardiovascular risk.'However higher doses of caffeine may have more harmful effects.'Before much caffeine has actually entered the bloodstream, the brain is already responding. Taste receptors send signals to the brain which activate parts of the nervous system associated with alertness and reward. This is why some people feel a mental 'lift' after the first sip, even though the caffeine hasn't had time to reach the brain. However some experts say the immediate shift in mood is likely a placebo rather than a biological change – especially if you drink coffee every morning. The real energy boost comes 20 minutes after After about 20 minutes is when you will start to feel caffeine's effects, Dr Duane Mellor, from the British Dietetic Association, explains. Within ten minutes of the first sip, your mental performance has already improved, making you feel more alert and ready to start the day.'After about 10 minutes the caffeine will appear in the blood,' he said.'Some can be absorbed through the mouth and stomach but only smaller amounts, most of the absorption is in the first part of the intestines.'Once the caffeine in the coffee is absorbed, that's when you feel that tell-tale energy boost.Mid-morning jitters Most people reach peak caffeine levels around 30 minutes to an hour after drinking coffee.As caffeine is released into the bloodstream, adrenaline starts to rise – triggering the 'fight or flight' response. Concentration levels improve incrementally from here, as blood flow to the brain increases, driving up blood pressure. At this stage, alertness is near maximum, dopamine activity may slightly increase – resulting in improved mood and motivation – and some people may feel more productive. But following this high we associate with the morning cup, those of us who are more sensitive to caffeine may start to experience feelings of anxiety, heart palpitations and tremors. For these people, drinking coffee with food can help delay the rate at which caffeine is absorbed into the bloodstream. Nature calls Caffeine is a diuretic, so once the stimulating effects kick in, you may feel the need to urinate more frequently. When caffeine enters the bloodstream, it inhibits the production of a molecule called adenosine, which normally helps promote the reabsorption of water back into the bloodstream. When this response is blocked, the body takes in less water, increasing urine output. But this doesn't necessarily mean that coffee is dehydrating, research suggests. The diuretic effect is relatively mild and the body develops tolerance over time. One 2014 study found that a small cup has no links to dehydration, meaning those who drink coffee in moderation don't need to compensate by drinking more water. However, the diuretic effect will be more noticeable when you consume larger doses of caffeine in a short period or when you are already dehydrated. Hunger pangs The compounds of coffee stimulate the release of a hormone called gastrin in the gut, which tells the stomach to produce more acid. In some people, this can help aid digestion and relieve symptoms of constipation. However, others may experience mild feelings of indigestion, heartburn or acid reflux. Decaf coffee can also trigger some of these responses, as they are triggered by the polyphenols in the beans rather than caffeine itself. One of the fastest gut responses is increased activity in the large intestine – which can be felt just four minutes after drinking coffee. This explains why some people feel the need to use the toilet almost immediately after finishing their morning cup. But the good news is, regular consumption of coffee appears to positively alter the composition of the gut microbiome – the friendly community of bacteria living in the gut.Research suggests that regular coffee drinkers may have greater abundance of beneficial gut bacteria, which help reduce the risk of bowel cancer and inflammation while crowding out harmful microbes. One 2017 review, including over two million participants, found that colon cancer risk fell by around seven per cent for every four cup increase in coffee intake. The dreaded mid-afternoon caffeine crashAs a general rule, caffeine has a half-life of six hours, meaning it will be in your system hours after your first sip. But as exhaustion-inducing adenosine gradually accumulates in the brain as the effects of caffeine wear off, sleep pressure increases. This can feel like a sudden drop in energy, concentration and motivation, often described as a 'crash'. Common signs include brain fog, fatigue, irritability, headaches and lower motivation.And if you have your first coffee around 9am in the morning, the likely crash coincides with the body's natural afternoon dip in alertness, making the crash feel even worse. One more can't hurt... can it? For a while after the caffeine has left your system, it will still be very much on your mind – as receptors in your brain wait for another hit. This expectation results in many of us reaching for another cup as we start to feel the warning signs of a slump.But one of the best ways to avoid the crash, or at least make it more bearable, is to avoid repeated caffeine hits through the day, experts say. Due to its long half-life, it is widely accepted that consuming caffeine late in the day can interfere with sleep. One study, published in the Journal of Clinical Sleep Medicine, found that caffeine consumed six hours before bed still affected sleep – even when participants said they could no longer feel its effects. And so the cycle repeats itself; a poor night's sleep remedied by a strong coffee in the morning.