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How much coffee is it safe to drink?

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New British research suggesting people can drink up to 25 cups of coffee a day without damaging their arteries has created a buzz around the world. John Elder looks at what the study does, and doesn’t, say about safe caffeine levels.

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You’ll never sleep again – new research partly funded by the British Heart Foundation has found people can drink up to 25 cups of coffee a day with no damage to their arteries.

This contradicts one line of previous research, and is supported by another – but it’s the 25-cup-a-day claim that’s prompted a splash of media panic.

“No, You Probably Shouldn’t Drink 25 Cups of Coffee a Day,” bleats TIME.

“An expert explains the long list of reasons to keep your habit to a few cups per day,” cautions the HuffPost.

Well, sure. And when it comes to coffee, there are experts frothing fast and furious all over the joint.

The long and the short (black) of it

To calm things a little: The new study doesn’t advocate you swallowing a couple of dozen long blacks – it simply found that up to that manic level of consumption your arteries won’t stiffen, increasing your risk of stroke or heart attack.

To reach this conclusion, researchers from Queen Mary University of London enlisted 8412 participants who underwent MRI heart scans and infrared pulse wave tests.

These provide useful information regarding the mechanical properties of the arterial tree and the ventricular-vascular interaction, and can also be used to assess what’s called the endothelial function.

The endothelium is a thin membrane that lines the inside of the heart and blood vessels. The cells in this membrane release substances that control vascular relaxation and contraction, as well as enzymes that control blood clotting, immune function and platelet adhesion.

In the study, coffee consumption was categorised into three groups: Those who drink less than one cup a day, those who drink between one and three cups a day and those who drink more than three.

People who consumed more than 25 cups of coffee a day were excluded – possibly because they couldn’t be made to sit still for very long.

But according to a statement from the British Heart Foundation: “No increased stiffening of arteries was associated with those who drank up to this high limit (25 cups) when compared with those who drank less than one cup a day.”

The association between drinking coffee and artery stiffness measures were corrected for contributing factors like age, gender, ethnicity, smoking status, height, weight, how much alcohol someone drank, what they ate and high blood pressure.

Previous suggestions that drinking coffee leads to stiffer arteries are inconsistent and could be limited by lower participant numbers, according to the researchers, led by Professor Steffen Petersen.

There is no peer-reviewed paper as yet, because the findings were presented this week at the British Cardiovascular Society Conference in Manchester.

Dr Kenneth Fung, who led the data analysis for the research at Queen Mary University of London, said in a statement: “Despite the huge popularity of coffee worldwide, different reports could put people off from enjoying it. Whilst we can’t prove a causal link in this study, our research indicates coffee isn’t as bad for the arteries as previous studies would suggest.”

“Although our study included individuals who drink up to 25 cups a day, the average intake amongst the highest coffee consumption group was five cups a day. We would like to study these people more closely in our future work so that we can help to advise safe limits,” Dr Fung said.

Hold up – it’s not all good news

The research, however, indicated that more ardent coffee enthusiasts weren’t necessarily pursuing a healthy lifestyle.

“Moderate and heavy coffee drinkers were most likely to be male, smoke, and consume alcohol regularly,” the foundation said.

A study published last year from the US National Cancer Institute found drinking coffee was associated with a lower risk of early death – up to eight cups a day.

There have been caffeine-related deaths but these were largely a consequence of drinking too many energy drinks, with the victims usually teenagers with heart conditions.

A judge in California this week ruled that local coffee shops weren’t required to post cancer warnings on the basis that coffee doesn’t contain a dangerous amount of hazardous chemicals.

This article was first published on The New Daily.

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