We used to be a nation defined by our tea-drinking, but coffee is now the UK’s favourite drink, with 63 per cent of us regularly imbibing compared with 59 per cent for tea, according to a 2023 survey.
And rarely a month passes without another scientific study suggesting that all that coffee is good for our health.
One of the most recent showed that coffee drinkers are happier in the first two-and-a-half hours of the day than abstainers.
This is probably because caffeine blocks the absorption of a compound in our bodies – adenosine – that makes us feel sleepy.
‘This increases the release of dopamine, a feel-good chemical that helps improve mood and alertness,’ explains Professor Anu Realo, head of the wellbeing, culture, and personality research group at the University of Warwick, who led the research.
The effect might also be due to minor caffeine withdrawal effects – which make you feel tired but then ‘disappear after the morning coffee’, she adds. Unsurprisingly, that makes you feel happier.
The health benefits emerging from research are significant, with large studies linking coffee-drinking with a lower risk of conditions such as type 2 diabetes, coronary heart disease and stroke, possibly due to antioxidants, compounds that can help lower inflammation, in the beans.
Last November, the American Heart Association published research showing that for adults who’d previously suffered from atrial fibrillation (a faulty heart rhythm), a cup of coffee a day was associated with a 39 per cent lower likelihood of recurrence.
A recent study showed that coffee drinkers are happier in the first two-and-a-half hours of the day than abstainers
Coffee is always near the top of the list of tooth-staining culprits. But new research suggests the type of bean can impact the level of discolouration
‘Coffee increases physical activity which is known to reduce atrial fibrillation – caffeine is also a diuretic, which could potentially reduce blood pressure’ lessening the risk, said the researchers.
But there can be downsides – from tooth staining to anxiety. How you make it and the beans you choose, also matter…
Why bean choice makes a difference
We generally consume two species of coffee bean – robusta and arabica, explains Christopher Hendon, an associate professor of chemistry at the University of Oregon and a leading coffee scientist.
Robusta beans, grown mainly in Vietnam, Indonesia and parts of Africa, typically have a deep, strong flavour, high caffeine content and are more acidic. They’re generally used for instant coffee.
Arabica beans, which account for 70 per cent of the world market and are mainly grown in South and Central America, are more aromatic and taste chocolatey; they’re lower in caffeine, too, says Professor Hendon (who only drinks one cup of filter coffee each morning because he tries so much at work).
The type of bean affects its health credentials, too.
Robusta has about double the caffeine and is richer in chlorogenic acid, an antioxidant, but this may cause more digestive irritation for sensitive people.
Arabica, as it’s generally lower in caffeine and acidity, is gentler on the stomach and contains more trigonelline, an alkaloid beneficial for liver and brain health, through its antioxidant, anti-inflammatory and metabolism-regulating properties.
The worst type for staining teeth
Coffee is always near the top of the list of tooth-staining culprits. But new research suggests the more chlorogenic acid in it, the more it stains.
Adding milk can help because the proteins in it, such as casein, can bind to the acidic plant compounds in coffee, preventing them from adhering to tooth enamel.
The study, published last year in the American Journal of Dentistry, also found hot coffee appeared to be worse for discolouration than iced coffee.
It’s not just about caffeine
Coffee is packed with more than 1,000 bioactive compounds, including oils, carbohydrates and proteins, as well as antioxidants.
Indeed, because we drink so much of it, coffee is one of the largest sources of antioxidants in our diets, says Professor Hendon, with chlorogenic acid potentially the most interesting.
‘It’s not just about the volume you are drinking – it’s about the concentration of the coffee you have,’ says Professor Christopher Hendon, a leading coffee scientist
Coffee is packed with more than 1,000 bioactive compounds, including oils, carbohydrates and proteins, as well as antioxidants
‘Roasted coffee is one of the only sources of chlorogenic acid on Earth – it comes from the acids in coffee decomposing when it’s roasted.’
It can be broken down and transformed by gut bacteria into multiple potentially beneficial molecules such as caffeic acid, which is anti-inflammatory.
A 2024 study by Harvard University found gut microbiomes of coffee drinkers were ‘markedly healthier than non-drinkers’ – with analysis showing that 115 bacterial species react positively to the drink, reported Nature Microbiology, meaning there were more beneficial ones and fewer harmful bacteria.
How much is enough – or too much?
Research points to around three to four cups a day as optimal for health – this would give around 400mg of caffeine, the amount the European Food Safety Agency recommends adults should not exceed per day.
While caffeine tolerance varies between individuals, if you regularly drink more than that you risk short-term side-effects such as insomnia, anxiety, increased heart rate and digestive issues. But working out how much caffeine is in your regular cup at home or in a coffee shop can be difficult. It varies due to natural variations in coffee beans themselves – and different ways of making your drink.
‘It’s not just about the volume you are drinking – it’s about the concentration of the coffee you have,’ says Professor Hendon, who explains that in the industry two parameters are used to judge a drink’s strength: efficiency of extraction and concentration.
‘It’s pretty standard to extract 2g coffee dissolved in water from 10g of ground coffee, which is a 20 per cent extraction,’ he explains. ‘If I put that 2g in 100ml of water, my drink is 2 per cent concentrated.
This is what you might commonly find in a shorter drink such as an espresso. A cappuccino often contains two ‘shots’ of espresso – still at 2 per cent concentration – but then will be further diluted with milk and water, so the concentration of coffee overall will vary.
How long the hot water touches coffee is also key – longer means more caffeine and other coffee molecules make it into the cup.
‘As a result, coffee preparations that are made with a short contact time such as espresso [or even a cappuccino] tend to have lower concentrations of certain molecules, including beneficial plant compounds – even though we think of espresso as strong.’
So actually the caffeine content in espresso is lower – somewhere between 40-80mg, while it can be upwards of 150mg in a cup of filter coffee.
This means you could have as many as five espressos in a day, but only three to four cups of filter coffee. But the filter may have more healthy compounds.
Brain booster delusion
However, some experts are cautious in recommending coffee as a health panacea. Professor Peter Rogers, a psychologist at the University of Bristol, who has studied what caffeine does to the body, says: ‘One key effect is wakefulness – but another is anxiety and increased blood pressure.’
The latter effect is usually small and temporary but in some people (especially non-habitual drinkers) it can be pronounced.
Caffeine raises blood pressure by blocking adenosine and triggering the production of adrenaline, which causes blood vessels to constrict.
‘We become completely or partly tolerant when we drink coffee regularly,’ says Professor Rogers.
Caffeine withdrawal can occur at surprisingly low daily intakes. ‘But the severity depends heavily on dose, timing and individual sensitivity,’ he adds.
The withdrawal effect is probably down to vasodilation, the widening of blood vessels – in this case particularly in the brain, where adenosine receptors are blocked by caffeine.
‘When you come off the caffeine, you begin to vasodilate more effectively again. It’s this return to normal which is the cause of your headache,’ he explains.
As for boosting your brain: ‘Coffee can be useful for keeping you awake but, actually, it may not improve cognitive performance.
And if it causes anxiety this is distracting – your brain is searching the environment for threats, which is actually impairing your performance,’ adds Professor Rogers (who drinks only decaf coffee unless he has a long drive.)
What about instant coffee?
Instant coffee has had a health-conscious makeover with newer brands adding ingredients to their blends, such as ‘adaptogens’ (plant compounds said to help the body cope with stress), including mushroom extracts and ashwagandha – an evergreen shrub.
Zain Peer, of the instant-coffee company London Nootropics, says: ‘We are coffee snobs and we wanted to make ground coffee, but then we realised that depending on how you filter it, you might be filtering out the active compounds. So, we use spray-dried coffee and then 8-10 per cent of more finely ground (microground) coffee, too, for flavour. With instant you can control what someone is getting.’
But Professor Hendon isn’t convinced: ‘There are no good examples where adding something to coffee has an enhanced effect compared to taking the additive by itself.’
He also argues that spray-dried instant might potentially produce more unwanted by-products.
Instant coffee is typically freeze-dried – ‘this means it starts as a baking tray of liquid and comes out as a solid and then gets broken up into solid little pieces’.
‘By comparison, spray drying involves taking a liquid extract and aerosol spraying it into an oil drum and then scraping the coffee off the sides. It behaves more like dust. You are heating the coffee twice which could potentially increase the presence of compounds like acrylamide.’
Acrylamide is formed when certain foodstuffs are heated to high temperatures, and is considered a carcinogen – however, the amounts in spray-dried instant coffee are well within safe levels, adds Professor Hendon.
Perhaps it pays to remember that it might not be what’s in our cup that matters most.
‘Part of the reason coffee improves our morning mood may come from the ritual itself,’ says Professor Anu Realo, who is particular about the two cups of coffee she drinks each morning. She uses freshly ground beans, preferring ‘dark roast arabica beans’, in a bean-to-cup espresso machine. Each cup contains two espressos, with a third of frothed milk.
‘For many people, even the smell or anticipation of coffee can lift their mood. It’s not just the caffeine, the taste and experience matter, too. I enjoy every sip.’
Using the right water counts, too
Professor Hendon says it’s crucial to consider the water you use.
‘Hard water yields not-very-good coffee in terms of flavour. It’s high in calcium and sodium bicarbonate which strips out some of the coffee’s natural acidity.’
One option is bottled water, but it’s neither an environmentally sustainable option nor always soft – Evian, for example, ‘has lots of bicarbonate in it, hence its silky mouthfeel, but that means it’s about 50 per cent harder than London water, so it’s not good for coffee’. Or ‘you can buy coffees whose flavour profiles are not as affected by the water chemistry’, says Professor Hendon. ‘These tend to be cheaper coffees, such as varieties from Brazil. They don’t have a lot of acid to begin with anyway.’
If you grind your own beans, store them in the freezer. ‘It not only helps preserve the beans, but they undergo a material transition so they fracture in a more consistent way when you grind them up, meaning the flavours come out more reliably.’
