The risk is particularly high for pregnant women - who should have a maximum of two cups a day - and young people.
In its first guidelines on caffeine consumption, the EU’s food safety watchdog has advised a daily limit of 400mg.
The average mug of instant coffee contains around 100mg of caffeine.
Consuming the caffeine equivalent of four espressos a day is harmful to health, the EU food safety agency said today
The European Food Safety Agency warned those who break the limits run the risk of a host of health problems, from anxiety and sleeplessness to heart rhythm disturbances and heart failure. Its comprehensive review of literature on the subject also showed links between high caffeine intake in pregnancy and having a baby that is underweight. The NHS warns that too much caffeine can cause a miscarriage. There are also links to birth defects.
With the average espresso containing 80mg, the 400mg limit for adults equates to five espressos.
However, some large coffees from High Street chains contain several shots of espresso - meaning someone could breach the daily limit after just a couple of cups. And a large, filter coffee from Starbucks, contains 400mg in a single cup.
As a result, health-conscious men and women may be unwittingly putting their health at risk, just by having a coffee or two during the working day.
However, with coffee far from the only food or drink to contain caffeine, EFSA also warned that many people may unintentionally be going over the safe limit.
The average cup of tea contains 50mg, while Red Bull has 80mg per can. A small bar of plain dark chocolate has up to 50mg of caffeine, while milk chocolate has around half that.
Coke, a drink often perceived as being high in caffeine, has just 30mg per can. Caffeine is also often added to painkiller pills to given them an extra kick.
Caffeine: Table shows a range of drinks in order of caffeine content and their relation to daily allowances
Emilie Combet, a lecturer in human nutrition at Glasgow University, said: ‘Caffeine is in many things. It’s in some chocolate and some energy drinks and some drugs, so on occasion, some people might go over the limit quite innocently.’
She added that caffeine levels in coffees in cafes vary widely, making it hard for customers to know what they are drinking.
A recent Glasgow University analysis of espressos from 20 coffee shops found huge variations in the amount of caffeine, with the strongest having six times as much as the lowest.
Men who drink one or two mugs of coffee a day are less likely to suffer from erectile dysfunction, a study has found.
According to NHS data, one mug of instant coffee contains about 100mg of caffeine, while a mug of filter coffee contains about 140mg.
A cup of tea and a can of cola contain 75mg and 40mg, respectively.
Researchers found that men who drank between 85mg and 170mg of caffeine daily were 42 per cent less likely to report impotence than those who drank none.
And those who drank between 171 and 303mg of caffeine were 39 per cent less likely.
Dr Combet said: ‘The biggest difficulty for people is choosing their coffee because when you order it, you don’t know what is coming in the cup.’
Deciding a recommended limit was a request of the European Commission, in an effort to find a Europe-wide benchmark for caffeine consumption.
The European Food Safety Authority carried out the scientific study after some countries raised concerns about the health effects of caffeine on the heart and central nervous system, as well as possible risks to foetuses.
'The main message of the report is that consumers must account for caffeine consumption from sources other than coffee,' an EU spokesman told AFP.
'The health risk is not enormous, but it exists,' he added.
The view of the EFSA echoes that of the U.S. Food and Drug Administration, which has also cited 400 mg of caffeine daily as an amount not generally associated with negative effects.
Britain doesn’t have a guideline amount for healthy adults. But, like the EU, it does advise that pregnant women limit themselves to 200mg of caffeine a day.
Martin Wattam, of the British Coffee Association, said: 'Coffee consumption is an important part of our culture in the UK, with over 70 million cups of coffee consumed every day.
'The British Coffee Association welcomes EFSA’s conclusion that moderate daily caffeine intake up to 400mg - equivalent to 4 to 5 cups of coffee - doesn’t raise any safety concerns for adult drinkers and may actually have some health benefits.
'It should be underlined that the 400mg figure is a recommendation for safe daily caffeine use, not a tolerable upper limit.'
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