The newest review of the literature on caffeine and its effect on the rhythm of the heart shows that the drug is safe for people with atrial or ventricular arrhythmias, an abnormal heart rhythm. Even more, caffeine proves to be beneficial for this population, with evidence showing that it can reduce the frequency of arrhythmias.
Atrial fibrillation (AF) is the most common type of heart rhythm disorder, characterized by a rapid and irregular heartbeat. AF can cause stroke if untreated. Along with other arrhythmias, AF can go unnoticed, and it can either be harmful or increase the risk for sudden cardiac arrest. Needless to say, scientists want to be able to advise at-risk populations of the right lifestyle choices to minimize their risk of adverse cardiac events.
"There is a public perception, often based on anecdotal experience, that caffeine is a common acute trigger for heart rhythm problems," said lead author Peter Kistler, MBBS, PhD. "Our extensive review of the medical literature suggests this is not the case."
Caffeine stimulates the entire central nervous system, blocking the effects of a chemical called adenosine, which can contribute toward AF. The average cup of coffee has about 95 milligrams of caffeine, and the average cup of tea has 27 milligrams.
The recent review included an analysis of multiple population-based studies. Researchers looked for any connection between caffeine intake and arrhythmias. They observed a decrease in AF linked with an increase in caffeine intake, and they found that caffeine has no effect on ventricular arrhythmias, even when individuals drank up to six cups of coffee, equal to 500 milligrams of caffeine.
In addition to being harmless, the review found that, in the long-run, caffeine may be beneficial in the context of arrhythmias. This is thanks to antioxidants in coffee and tea that occur independently of caffeine and because caffeine inhibits adenosine.
A 2017 study showed that coffee contains beneficial amounts of a polyphenolic compound called chlorogenic acid. This polyphenol provides antioxidant and anti-inflammatory effects that are particularly helpful for athletes and post-exercise recovery. The study showed that the best source of chlorogenic acid comes from lightly roasted, finely ground, high-altitude coffee beans.
"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,” Kistler explained.
The results are not the same for energy drinks, which contain between 160 and 500 milligrams of caffeine per beverage.
The present study was published in the journal JACC: Clinical Electrophysiology.