For some it is an essential pick-me-up and no day can start without it. Others believe drinking it has numerous health benefits, citing studies that suggest regular consumption could combat everything from heart disease to dementia. But coffee – which last year overtook tea as Britain’s favorite hot drink – doesn’t agree with everyone. Reports suggest that even modest amounts can cause anxiety, palpitations and sleepless nights.
The cause, of course, is caffeine – the stimulant that is one of the main components of coffee.
But why do people react badly? We spoke to coffee experts to find out – and they revealed the surprising ways you can maximize the benefits and enjoy the buzz while avoiding the downsides.
Coffee – which overtook tea as Britain’s favorite hot drink last year – doesn’t agree with everyone
In 2019, pop megastar Taylor Swift said L-theanine was her favorite supplement because it helps with her ‘stress and anxiety’
SENSITIVITY TO COFFEE IS IN OUR GENES
Experts say that different reactions to coffee are in our DNA. Caffeine can linger in the body for anywhere from 90 minutes to nine hours, depending on how quickly the liver – the organ that filters toxins from the blood – breaks it down.
Scientists have discovered that a specific gene, CYP1A2, determines how quickly the liver processes caffeine. About half the population has two copies of the CYP1A2 gene, meaning they burn caffeine quickly. About four in ten have only one copy of the gene, which helps coffee stay in their system longer. And about one in ten does not have a CYP1A2 gene. Their bodies can still break down caffeine, but it’s significantly harder for them, meaning the stimulant stays in the blood for much longer, increasing the risk of sleep loss.
Some research suggests that people without the CYP1A2 gene may even develop high blood pressure as a result of drinking coffee. ‘Many people can metabolize coffee very quickly, meaning they get an instant energy boost,’ says Flick Lucas, sports nutritionist at Oxford Brookes, who is researching the effect of giving athletes caffeine before competition.
‘But some don’t get that benefit and the caffeine can stay in the body for up to nine hours, causing unwanted symptoms. It is only in the last few years that we have begun to understand how big a role genetics plays in this effect.’
WHY TOO MUCH MAKES YOU FEEL TERRIBLE
Coffee – or more accurately caffeine – works by changing the flow of certain compounds and chemicals to the brain.
In order to sleep, the body produces a chemical called adenosine. When absorbed into the brain, it makes people feel tired and slows the heart rate. During the day, the amount of adenosine in the body builds up. Therefore, it is normal to start feeling sleepy in the afternoon.
But caffeine blocks the receptors in the brain that process adenosine. ‘This will make you feel more alert and awake,’ says Dr Duane Mellor, a dietitian at Aston University. There are of course disadvantages to this. “You don’t want to be on alert all the time with your heartbeat pounding,” adds Dr. Mellor.
‘Adenosine also has a calming effect on the body, so taking it away for long periods of time can make people feel anxious.’ Experts say that people who drink coffee regularly are less sensitive to its effects because their adenosine receptors build up caffeine resistance.
Research also shows that people who smoke are less affected by coffee, because their adenosine receptors are already dulled by the effect of tobacco. However, studies suggest that genes are the most important factor in how coffee affects the body.
JITTING? Blame that cheap instant
Experts say the type of bean used to make the coffee affects the amount of caffeine it contains. There are two coffee beans used by the vast majority of producers: arabica and robusta.
Arabica, the more expensive and popular bean, grows higher up in the mountains.
It tends to have a sweeter taste. But Robusta contains 40 percent more caffeine. Most coffee shops only use Arabica beans. The same applies to more expensive instant coffee such as Nescafe Gold Blend. However, cheaper instant varieties, such as Nescafe Original, contain a mix of arabica and robusta, which can cause them to have a higher caffeine content. Even more important is the way the coffee is prepared, experts say.
At its most basic level, coffee is a combination of water and ground coffee beans, but the preparation can make a big difference to the caffeine content. ‘The more contact time there is between the coffee and the water, the more caffeine the drink will contain,’ says Kurt Stewart, founder of Volcano Coffee Works in South London. ‘So American filter coffee (where hot water is passed through the ground beans and a paper filter) will never be very caffeinated, which is why you can drink it all day long.
‘The most caffeinated coffee is cold brew, where the ground beans are soaked in cold water for up to 24 hours. If you are sensitive to caffeine I would avoid cold brew. The espresso machine stuff you would normally get at a coffee shop is somewhere in the middle on the caffeine scale.
“It’s fine to drink small amounts, but you wouldn’t want more than a few in a short period of time.”
ESPRESSO OVERDOSE? HERE’S WHAT TO DO
Scientists say there are steps people can take to counteract the unwanted effects of caffeine.
Research shows that drinking plenty of water – roughly one large glass for every coffee – can reduce the risk of jitters. This is because coffee is a diuretic, meaning it dehydrates the body. Experts say this can worsen the side effects of coffee. That’s why they recommend drinking plenty of water if you feel like you’re consuming too much caffeine.
Research also shows that vigorous exercise – for example running or cycling for 20 minutes – can reduce anxiety about coffee after it starts, and reduce the risk of sleepless nights.
Experts claim that this is likely due to the fact that exercise speeds up the metabolism of caffeine, causing it to be broken down more quickly.
In recent years, there has been growing popularity for a supplement called L-theanine, which some social media influencers claim can take away the jitters if taken before drinking coffee.
L-theanine is an amino acid found in black and green tea. In supplement form, it usually comes as a flavorless soluble powder (this can be mixed into a protein shake and some people also mix it directly into coffee). There have been some studies suggesting that it has an anti-anxiety effect.
In 2019, pop megastar Taylor Swift said L-theanine was her favorite supplement because it helps with her “stress and anxiety.” Experts say there are suggestions that people may benefit from L-theanine. ‘Many people claim that drinking tea, which often contains as much caffeine as coffee, does not make them anxious,’ says Dr Mellor.
‘It is possible that this is because it contains L-theanine. The studies claiming it works as an anti-anxiety supplement are too small to draw any firm conclusions, but the science makes sense.”
DECAFF CAN HELP MORE THAN YOU THINK
One reason researchers believe coffee may have health benefits is that it contains polyphenols, a group of compounds found in plants that are believed to have anti-inflammatory properties. Recent research also suggests that it contains a surprising amount of fiber – a crucial nutrient found mainly in fruits, vegetables and grains.
Professor Tim Spector, a British epidemiologist and creator of the Zoe nutrition app, claims that people who drink three to four cups of coffee a day get ‘significant amounts of fibre’.
Research shows that coffee contains about 1.5 grams of fiber – about the same as a glass of orange juice. The NHS recommends that people consume around 30 grams of fiber a day, but research shows that less than a tenth of Britons get enough fibre.
Decaffeinated coffee is usually made by steeping fresh coffee beans in hot water. Because caffeine is water-soluble, this process removes about 97 percent of the stimulant, but the rest of the ingredients are left behind.
‘Decaffeinated coffee still contains the beneficial ingredients,’ says Dr Mellor.
‘And it is possible that it will also give you an energy boost. For many people, having coffee is more about the habit than the caffeine; it’s a taste they associate with starting the day. And you still get that bitter taste from decaf.’
Experts say demand for decaffeinated coffee is increasing.
“We’ve seen a significant increase in the number of customers requesting it,” says Kurt Stewart.
“A lot of people feel like it still gives them the coffee buzz without the jitters; it’s a kind of placebo effect.’
And for those who are skeptical of this theory, there is good news.
“Earlier this year we tested a half and half coffee, a combination of caffeinated and decaffeinated,” Mr Stewart added.
‘It was extremely popular, especially with people who are more sensitive to caffeine and people who want to drink it later in the day.
“We’re going to sell more of it and I think others might do the same.”
…but be careful: too much caffeine can be really fatal
It’s not just an urban myth: According to studies, you really can overdose on coffee.
In 2022, a 29-year-old British man died of cardiac arrest after accidentally consuming “up to 5 grams” of caffeine powder (not coffee).
Thomas Mansfield, a personal trainer who used caffeine to boost his energy levels while working out at the gym, drank seven times the recommended dose, an inquest heard.
An Italian study published in 2018 found 92 similar cases of caffeine overdose deaths in the medical literature. These deaths also involved the consumption of more than 5 grams of caffeine. A standard cup of coffee usually contains between 80 and 100 mg of caffeine. This means you need to drink 50 cups to overdose. But drinking more than 500 mg has been linked to uncomfortable side effects, including heart palpitations and increased blood pressure.
Research shows that for non-exercisers, around 250 mg – roughly two and a half coffees – is an optimal amount of caffeine, and is linked to desirable symptoms such as better concentration and even arousal.
However, experts say that for athletes, even a small cup of coffee is enough to give them an edge.
“We found that one shot of espresso can give athletes the boost they need,” says researcher Flick Lucas. “That’s only if you’re a fast metabolizer of caffeine, though.”
