Moderate caffeine consumption may not be as dangerous as initially believed.
Concerns about caffeine consumption in patients with heart failure are largely unfounded, based on a recent study that found no link between caffeine intake and increased risk of abnormal heart rhythms.
Published in JAMA Internal Medicine, this study explored the ongoing controversy around caffeine and abnormal heart rhythms. While studies have linked very high doses of caffeine to an irregular heart rhythm, called arrhythmia, there’s little evidence that moderate caffeine intake has the same effects. Still, many doctors recommend that certain patients avoid caffeine to help prevent arrhythmias or heart events, while others believe these concerns are unfounded.
To help settle the debate, researchers conducted a double-blinded randomized clinical trial, which is considered the gold-standard of research studies. This study design randomly assigns participants to an active intervention or inactive placebo, and ensures that both participants and researchers are unaware of which group they’re assigned to.
Conducted from 2013–2015, the study included patients with the most common cause of heart failure, called left ventricular systolic dysfunction, which occurs when the heart loses its ability to contract normally. This condition affects roughly 60% of patients with heart failure and significantly increases risk for an abnormal heart rhythm.
Through the trial, participants were asked to consume five cups of coffee over five hours, which together contained 500 mg of caffeine or no caffeine at all, and then participate in an exercise treadmill test. Participants’ heart rates were monitored over the entire period and blood samples were collected to monitor caffeine levels in the blood. Participants then repeated the process one week later, being assigned to the opposite group they were assigned to on their first visit.
The average age of participants was 61 years and most were male.
After analysis, researchers found no significant differences in abnormal heart rhythms among participants consuming 500 mg of caffeine vs. no caffeine either at rest or during exercise. When analyzing blood samples, researchers also found that higher levels of caffeine in the blood were not associated with a difference in abnormal heart rhythms.
Based on results, authors conclude that consuming high doses of caffeine does not immediately trigger abnormal heart rhythms in patients with heart failure. And combined with past research, authors conclude that there is no solid evidence to support recommendations about limiting caffeine intake to prevent abnormal heart rhythms.
However, it’s important to note that this study only applies to patients with heart failure caused by left ventricular systolic dysfunction. Also, the trial tested the effects of 500 mg of caffeine—the equivalent to 2.5–5 cups of coffee, depending on the strength. Therefore, the study does not suggest that it’s safe for patients at risk for abnormal heart rhythm to consume unlimited amounts of caffeine. Rather, it suggests that moderate caffeine consumption may not be as dangerous as initially believed.\