FOUR cups of coffee per day is the safe limit, scientists reckon as any more caffeine could strain your heart.
A study found consuming more than 400mg of caffeine each day raises blood pressure and heart rate, forcing the ticker to work harder.
Experts from Zydus Medical College in India said the quantity is equal to about four cups of coffee, 10 cans of Coke or two energy drinks.
Data from 92 healthy adults showed it made people slower to recover after a quick workout.
British coffee lovers drink an estimated 528 cups each every year – an average of one or two a day.
One in five participants in the study – 19.6 per cent – exceeded 400mg of caffeine daily.
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This could put otherwise healthy individuals at risk of high blood pressure
Dr Nency Kagathara
Lead author Dr Nency Kagathara said: “Regular caffeine consumption could disturb the parasympathetic system, leading to elevated blood pressure and heart rates.
“This could put otherwise healthy individuals at risk of high blood pressure and other cardiovascular events.
“Increasing awareness of these risks is vital to improve heart health.”
Millions of people drink coffee for its stimulant effects, which temporarily increase adrenaline and stress hormone cortisol to improve focus and alertness.
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Drinking too much can cause side effects like headaches, anxiety and feeling sick.
Dr Kagathara’s study, presented at an American College of Cardiology conference, measured people’s blood pressure and heart rate after a three-minute step test.
Heavy java drinkers had the highest readings after five minutes of rest following the workout, showing their hearts were weaker and slower to recover.
People who consumed more than 600mg of caffeine per day – about six coffees – had “significantly elevated” scores.
High blood pressure super-common in the UK
About a third of Brits have high blood pressure, equal to more than 10million adults.
It raises the risk of heart diseases, dementia, stroke and kidney failure, and many do not know they have it.
British Heart Foundation dietitian, Victoria Taylor, said: “A moderate amount of tea or coffee – four or five cups a day – should be fine for most people.
“Some people are more sensitive to caffeine and can experience palpitations, so then it’s sensible to avoid caffeine.”
How to lower blood pressure
Persistent high blood pressure (hypertension) puts extra strain on your blood vessels, heart and other organs and it can raise your risk of serious conditions like heart disease, heart attacks and stroke. Here's how to reduce it.
Reduce salt
Adults are recommended to limit their salt to 6g per day (around one level teaspoon) to avoid health consequences including high blood pressure.
The top tip is to swap out table salt, according to the Salt Substitute and Stroke Study, replacing it with a reduced sodium and added potassium alternative.
Cut down on alcohol
Excessive boozing can narrow the blood vessels, which raises the risk of hypertension.
Official drinking guidelines advise that people should not regularly drink more than 14 units a week to keep health risks from alcohol low.
Get moving
Exercise is good for the heart and the blood vessels.
Although the guidelines recommend 150 minutes of activity per week, if you're currently very inactive, just a walk to the shop every day is better than nothing, and you can work up from there.
Studies suggest that isometric exercises - when you hold the body in one position without moving, such as a wall squat or plank - are best for lowering blood pressure.
Stop smoking
Smoking cigarettes is a killer. It makes the arteries sticky and narrow, which can cause blockages.
While smoking is not a direct cause of high blood pressure, it can cause an instant rise to pressure, heart rate and reduce the amount of oxygen that gets to the body’s cells.
Skip coffee
Sadly, caffeine can cause a short, but dramatic increase in your blood pressure - even if you don't have high blood pressure.
Therefore cutting back on coffee is recommended as a lifestyle tip for those with hypertension.
Lose weight
The above tips can help you to lose weight, which is beneficial because being overweight in itself is a risk factor for hypertension.
Being overweight forces your heart to work harder to pump blood around your body, which can raise your blood pressure.
The only way of knowing whether you have high blood pressure is to have a blood pressure test. All adults over 40 years old are advised to have their blood pressure checked at least every five years.