Under normal circumstances, the heart beats 60 to 100 times per minute, with coordinated electrical surges that keep the rhythm steady. But sometimes the heart beats abnormally-either too fast, too slow, or in an erratic manner. These abnormalities, called arrhythmias, can cause disruptive and frightening symptoms. In the worst-case scenario, they can trigger a potentially fatal cardiac arrest (sudden cessation of an effective heartbeat).
According to a recent research review in JACC: Clinical Electrophysiology, most people with abnormal heart rhythms (atrial fibrillation or ventricular arrhythmias) can safely consume coffee and other caffeinated beverages in moderation, despite the common concern that caffeine can trigger arrhythmias.
After evaluating 19 major studies, the researchers concluded that “although there is no clearly defined threshold for caffeine harm, a regular intake of up to 300 milligrams a day [the amount in about three cups of coffee] appears to be safe and may even be protective against heart rhythm disorders.” However, they stated that there may be individual differences in reactions to caffeine, and that if someone does find that arrhythmias occur after caffeine consumption, then “avoidance is sensible.”