Cof­fee could keep your heart­beat go­ing strong

Nelson Mail - - COMMENT&OPINION - OLIVER MOODY The Times

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.

‘‘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 Kistler and his col­leagues 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.

Other 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.

Several 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.

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