Harvard Heart Letter

Heart Beat: Atrial fibrillation? Don't blame caffeine

Caffeine has long been suspected to be a trigger for atrial fibrillation, an all-too-common problem that turns the steady, coordinated beat of the heart's upper chambers into a fast, erratic churn. While it is possible that drinking eight cups of espresso in an afternoon could spark atrial fibrillation, moderate caffeine consumption has little effect on its development, according to a large Harvard-based study.

Researchers followed more than 33,000 participants of the Women's Health Study for 14 years. Over the course of the study, atrial fibrillation developed in just as many women in the group with the lowest caffeine intake, about one cup of coffee a week, as it did in the group with the highest caffeine intake, about six cups a day (American Journal of Clinical Nutrition, September 2010). The source of caffeine — coffee, tea, cola, or chocolate — didn't make a difference.

This study is in line with others showing little effect of moderate daily doses of caffeine on the development of atrial fibrillation. A few laboratory studies even suggest that moderate caffeine intake may help protect the heart against this problematic rhythm disorder.

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