Britain is a caffeine-powered country that drinks around 95 million cups of coffee every day.
And according to the latest research, we may be consuming much higher doses of the stimulant than we realize.
For example, a medium cappuccino from the popular Costa’s contains the equivalent of four Red Bull cans of caffeine, according to experts at Which? this week.
That’s 325 mg of the energizer and almost the full safe daily limit of 400 mg, or five cups of coffee.
In the meantime Fun A Manger’s espresso was found to be four times stronger than Starbucks’ version and contained 180mg of caffeine – almost half your total recommended daily intake.
Still, amid the various health warnings about the stimulant’s harms, some studies suggest that it may indeed provide benefits.
A 2026 study found that those who drank five or more cups a day were 47 percent less likely to develop liver problems. cancerwhile other research has found that coffee lovers have a lower risk of heart disease thanks to the anti-inflammatory substances known as polyphenols.
So what exactly happens after that very first sip? Here, experts reveal the body-wide impact of caffeine throughout the day…
Once you have a cup of coffee in the morning, you may find yourself wanting more throughout the day, experts say
The first sip: the immediate ‘buzz’
The effects of caffeine depend on how much you consume, but are felt almost immediately from the first sip.
“Caffeine consumed in coffee is an important part of daily life for millions of people,” says Dr. Gregory Marcus, chief of cardiology research at the University of California.
‘For most adults, intake of up to 400 mg per day – about five cups – without added sugars is safe and does not increase cardiovascular risk.
‘However, higher doses of caffeine may have more harmful effects.’
Before much caffeine actually enters the bloodstream, the brain already reacts.
Taste receptors send signals to the brain that activate parts of the nervous system related to 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 mood change is likely a placebo rather than a biological change, especially if you drink coffee every morning.
The real energy boost comes 20 minutes later
After about 20 minutes you’ll start to feel the effects of caffeine, explains Dr Duane Mellor of the British Dietetic Association.
Within ten minutes of the first sip, your mental performance will be improved, leaving you feeling more alert and ready to start the day.
“After about ten minutes, the caffeine will appear in the blood,” he said.
‘Some can be absorbed through the mouth and stomach, but only in smaller amounts. Most of the absorption takes place in the first part of the intestines.’
Once the caffeine is absorbed into the coffee, you’ll feel that telltale energy boost.
Mid-morning jitters
Most people reach their maximum caffeine levels about 30 minutes to an hour after drinking coffee.
As caffeine is released into the bloodstream, adrenaline begins to rise, triggering the “fight or flight” response.
From here, concentration levels improve incrementally as blood flow to the brain increases, causing blood pressure to rise.
At this stage, alertness is near maximum, dopamine activity may increase slightly – resulting in better mood and motivation – and some people may feel more productive.
But after this high we associate with the morning cup, those of us who are more sensitive to caffeine may begin to experience feelings of anxiety, palpitations, and tremors.
For these people, drinking coffee with food can slow the rate at which caffeine is absorbed into the bloodstream.
Nature calls
Caffeine is a diuretic, so once the stimulant effects kick in, you may feel the need to urinate more often.
When caffeine enters the bloodstream, it inhibits the production of a molecule called adenosine, which normally promotes the reabsorption of water in the bloodstream.
When this response is blocked, the body absorbs less water, causing urine production to increase.
But this doesn’t necessarily mean coffee is dehydrating, research suggests. The diuretic effect is relatively mild and the body develops tolerance over time.
A 2014 study found that a small cup is not linked to dehydration, meaning those who drink coffee in moderation do not need to compensate by drinking more water.
However, the diuretic effect will be more noticeable if you consume larger doses of caffeine in a short period of time or if you are already dehydrated.
Feelings of hunger
Coffee’s compounds stimulate the release of a hormone called gastrin in the intestines, 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.
Decaffeinated coffee can also cause some of these reactions, because they are caused by the polyphenols in the beans and not the caffeine itself.
One of the fastest intestinal reactions is increased activity in the large intestine – which can be felt as early as four minutes after drinking coffee.
This explains why some people feel the need to go to the toilet almost immediately after drinking their morning cup.
But the good news is that regular coffee consumption appears to positively change the composition of the gut microbiome – the friendly community of bacteria that live in the intestines.
Research suggests that regular coffee drinkers may have a greater abundance of beneficial gut bacteria, which help reduce the risk of colon cancer and inflammation while crowding out harmful microbes.
A 2017 study involving more than two million participants found that the risk of colon cancer decreased by about seven percent for every four cups of coffee increase in coffee intake.
The dreaded mid-afternoon caffeine crash
As a general rule, caffeine has a half-life of six hours, meaning it will be in your system for hours after your first sip.
But because exhaustion-inducing adenosine gradually builds up 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 symptoms include brain fog, fatigue, irritability, headaches and reduced motivation.
And if you drink your first coffee around 9 a.m., the likely crash coincides with the body’s natural midday dip in alertness, making the crash feel even worse.
One more won’t hurt…right?
After the caffeine leaves your system, you’ll think about it for a while – while the receptors in your brain wait for another craving.
This expectation has many of us reaching for another cup as we begin to feel the warning signs of a slump.
But one of the best ways to prevent the crash, or at least make it more bearable, is to avoid repeated caffeine injections throughout the day, experts say.
Due to its long half-life, it is generally accepted that consuming caffeine late in the day can disrupt sleep.
A 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; a bad night’s sleep remedied by a strong coffee in the morning.
