Caffeine may regulate heartbeat

OLIVER MOODY
April 17, 2018
The Times

Australian cardiologists have found a modest caffeine intake may protect the heart.

Drinking up to four cups of coffee a day is likely to curb the risk of abnormal heart rhythms, researchers have found.

In some studies caffeine, which is abundant in coffee, tea, chocolate and energy drinks, has been linked to changes in the “pacemaker” cells in the heart’s atrium. For this reason patients with an irregular heartbeat are sometimes advised to avoid it.

Yet a modest caffeine intake is probably mildly protective, according to a review of evidence by cardiologists in Australia.

While there are signs that caffeine may trigger a rapid and uneven heartbeat known as atrial fibrillation in a minority of people, it seems to have the opposite effect on most of us. In 2011 a study that followed 130,000 people for 17 years found that the 25 per cent who drank the most coffee were 40 per cent less likely to be hospitalised with arrhythmias than the 25 per cent who drank the least.

Another paper, published in 2014 and involving 228,000 participants, concluded that for every extra 300mg of caffeine a day – equivalent to three shots of espresso – the risk of atrial fibrillation fell by 6 per cent.

Peter Kistler, head of electrophysiology research at Alfred Hospital in Melbourne, and the senior author of the review, said that in the long run caffeine might help to limit biological stress and mitigate the damage to tissue from highly reactive oxygen molecules.

“Caffeinated beverages such as coffee and tea may have long term anti-arrhythmic properties mediated by antioxidant effects and antagonism of adenosine,” he said.

“In numerous population-based studies, patients who regularly consume coffee and tea at moderate levels have a lower lifetime risk of developing heart rhythm problems and possibly improved survival,” he said.

The paper by Dr Kistler and his colleagues, which is published in the journal JACC: Clinical Electrophy- siology, is a summary of research rather than new evidence in its own right.

It cites studies showing that high doses of caffeine flood heart cells with calcium and boost the levels of adrenaline in the brain and bloodstream.

In one experiment, however, rats were given 15mg of caffeine for every kilogram of body weight and all developed a form of heart arrhythmia known as ventricular fibrillation. To get an equivalent dose, though, humans would have to drink at least 30 cans of Coca-Cola or ten shots of espresso in a single sitting.

At least half a dozen groups of researchers have tried to get a more accurate picture of the risks involved by giving either caffeine pills or a placebo to people with a history of irregular heartbeat. Daily doses as high as 500mg, equivalent to approximately six cups of coffee, did not led to any greater danger of arrhythmia.

A number of large-scale studies have also shown that regular tea or coffee drinkers are less likely to die from heart problems and may also face a lower risk of stroke, heart failure and coronary heart disease.