Everything you need to know about what's in your cup of coffee 

One in three Irish people now buys coffee at least once a day - but can you get too much of a good thing? 

Sweet coffee aroma, coffee beans and morning coffee

Are you getting a bigger caffeine kick from your coffee than you bargained for? A recent report by the consumer watchdog, Which? compared the caffeine content in espresso, cappuccino and filter coffee from various high street chains, including Costa, Pret and Starbucks, and found some coffees provided five times as much caffeine as others.

If you are partial to a cappuccino from Costa on the way to work, you will certainly be buzzing through the morning as it was found to contain nearly five times as much caffeine as one from rival chain Starbucks. The survey found a “massive” 325mg of caffeine in a medium Costa cappuccino, about the same amount contained in four cups of tea. A Starbucks equivalent contained just 66mg of caffeine and there is 80mg caffeine in a 250ml can of Red Bull.

When it came to filter coffee, Pret a Manger (which opened in Dublin last year) provided the biggest hit with 271mg caffeine, two and a half times as much as the Starbucks version (102mg). And a single espresso from Pret provided 180mg of caffeine, six times as much as one from Starbucks (33mg). But there’s more to coffee than caffeine — here’s what you need to know about how it affects you.

How much coffee is safe to drink?

The European Food Safety Agency recommends adults consume no more than 400mg of caffeine, approximately four regular homemade cups of coffee a day. The Irish Heart Foundation (IHF) says “moderate intakes should not have a negative impact on the heart” and for most people up to four cups a day is fine, although advice for pregnant women is to consume no more than 200mg caffeine (two cups of coffee) daily.

More than 600mg caffeine a day has been linked to insomnia, nervousness, irritability, increased blood pressure and gastrointestinal problems. Remember too that cup sizes range from 30–700ml, so the amount of caffeine you get in a serving varies considerably as the Which? survey highlighted.

Individual sensitivity to caffeine varies.

“Some people are more sensitive to caffeine and find it gives them palpitations,” says Dr Angie Brown, medical director of the IHF and consultant cardiologist, “and very high levels of caffeine are a stimulant which can increase the heart rate, so make sure you check for caffeine sources in your diet other than tea and coffee.”

What are the health benefits?

There are reportedly more than 700 natural compounds in coffee including tannin, oils, carbohydrates and proteins as well as health-providing antioxidants.

“Coffee, like tea, is a plant-based food that naturally contains many beneficial compounds,” says Dublin-based dietician Sarah Keogh.

“Researchers have tried and failed for decades to find anything bad to say about coffee – apart from its caffeine content – and moderate consumption is linked to a decreased risk of some cancers and possibly to a lower risk of dementia.”

Because we drink so much of it – one in three Irish people now buys coffee at least once a day according to a survey by UCC Coffee Ireland – it is one of the biggest providers of antioxidants in our diets.

Will I cut caffeine by switching to tea?

Black, mate, matcha and green tea, all contain caffeine, albeit less than you get in a regular black coffee which provides 57mg of caffeine per 100ml while an espresso contains 55mg per 30ml shot (170mg per 100ml).

Generally, a mug of tea will provide roughly the same amount of caffeine as is found in an energy drink, which usually contains about 30mg of caffeine per 100ml (a 250ml can of Red Bull contains 80mg).

If you are someone who ‘waves’ a teabag briefly in the general direction of a mug of boiled water, there will be significantly less and, of course, many fruit and herbal teas contain none.

What about hidden caffeine?

Energy gels and drinks, cola, mocha and frappuccinos, ice lollies, painkillers, cold and flu capsules and even toothpaste can contain unexpected amounts of caffeine.

Look out for guarana, a popular energy-enhancing ingredient that is a natural source of caffeine in itself. You will also find caffeine in chocolate – although not in as high amounts as you might think with just 6mg of caffeine in 25g of milk chocolate and 20mg of caffeine per 25mg of dark chocolate.

“People are often surprised to find over-the-counter cold and flu medications contain caffeine,” says Keogh. “Often there is not much added, but it contributes to your daily intake.”

Does a coffee rating indicate its caffeine content?

If you select coffee according to the 1-10 strength rating that appears on many packets, you might assume you are getting an extra kick out of the ‘strongest’ variety. In fact, the number denotes the strength of roast rather than caffeine content or type of bean. The higher the number, the darker the roast and stronger the flavour. 

A light roast with a 1-3 rating might well contain as much caffeine as a punchier, dark roasted 7-8 coffee. Studies show the Robusta bean contains up to double the amount of caffeine as the Arabica bean.

Can too much caffeine seriously damage your health?

How much caffeine do you consume on a daily basis?

Some researchers have suggested that in excess of six to eight cups a day increases arterial stiffness, putting pressure on the heart and increasing the risk of a heart attack or stroke, although that was debunked in a study of more than 8,000 people presented at the 2019 British Cardiovascular Society Conference in which researchers reported that drinking up to 25 cups a day is not associated with having stiffer arteries.

Not everyone responds to caffeine in the same way and some people will get the jitters after just a cup.

Will coffee help you to lose weight?

The impact is likely to be negligible, but black coffee might help to shed a few pounds. Studies at Coventry University have shown caffeine ingestion prior to exercise can help people work that little bit harder so they burn a few more calories.

Others have suggested there might be bioactive compounds in coffee other than caffeine that help to burn fat and a study published in The Journal of Nutrition found that, women aged 45-69 who drank four or more cups of coffee a day had 4.1% lower total body and abdominal fat than non-coffee drinkers, and women aged 20-44 who drank two to three daily cups had the lowest levels of body fat, 3.4% lower than those drank no coffee.

In middle-aged men the effect was less strong, but two or three cups a day still seemed to result in 2% less abdominal fat than non-coffee drinkers.

Should I take black coffee early in the morning?

If you head for the coffee machine as soon as you get up, pause before pressing the button because it could have a negative effect on blood sugar control for the day, according to researchers at the University of Bath in Britain.

They showed that a poor night’s sleep did not worsen blood sugar responses at breakfast, compared to a normal night’s sleep, unless participants first drank black coffee when they got up in which case glucose metabolism deteriorated by around 50%.

“Our blood sugar control is impaired when the first thing our bodies come into contact with is coffee after a night of disrupted sleep,” says physiologist Professor James Betts who led that trial. “We might improve this by eating first and then drinking coffee later if we feel we still feel need it.”

Is it wise to avoid coffee after midday?

For some people even one cup of coffee in the afternoon can impact on their sleep.

“Our ability to metabolise caffeine declines as we get older so you might find that you need to drink your last cup by 2pm in order to sleep well once you reach your 50s,” Keogh says.

Even people who swear their sleep is not affected by late-night caffeine hits, are likely mistaken.

“Studies have shown that caffeine consumers who believe they sleep deeply after a shot or two don’t get the same sleep quality as they do without consuming caffeine,” Keogh says.

Will I suffer caffeine withdrawal if I cut down?

Many people suffer headaches, grogginess, and irritability for up to two weeks if they go cold turkey with caffeine. 

“The best option if you want to cut down is to reduce your intake gradually,” says Keogh.

One solution could be to wean yourself off the stronger stuff by switching to decaf. A new study in the Journal of Psychopharmacology reports that drinking decaf coffee can combat symptoms of withdrawal more effectively than drinking water.

This was particularly effective when coffee drinkers falsely believed they were drinking regular coffee and even those who knew they had drunk decaf experienced a significant drop in withdrawal symptoms.