Daily coffee may protect the heart in unexpected ways, according to a new clinical trial from the University of California, San Francisco (UCSF) and the University of Adelaide.
The study found that people who drink coffee every day have a significantly lower risk of atrial fibrillation (A-Fib), a condition that can lead to stroke and heart failure.
Doctors have long advised patients with heart rhythm disorders to avoid caffeine. Many feared it could trigger rapid or irregular heartbeats. But the new research, published November 9 in JAMA, found the opposite may be true.
Patients who drank at least one cup of caffeinated coffee or an espresso shot daily had a 39 percent lower risk of A-Fib recurrence compared to those who avoided caffeine.
The six-month randomized trial enrolled 200 adults with a history of atrial fibrillation or atrial flutter. All participants had recently undergone cardioversion therapy to restore a normal heart rhythm. Half were assigned to drink coffee daily. The others abstained from all caffeine, even decaffeinated coffee.
At the end of the trial, only 47 percent of those who drank coffee experienced another episode of A-Fib. In the group that avoided caffeine, 64 percent experienced a recurrence. The results challenge decades of conventional medical advice that linked caffeine to heart rhythm problems.
“Caffeinated coffee may protect against atrial fibrillation, at least among people that otherwise enjoy and tolerate caffeinated coffee,” said Dr. Gregory M. Marcus, senior author of the study and an electrophysiologist at UCSF Health. “Caffeine is also a diuretic, which could potentially reduce blood pressure and in turn lessen A-Fib risk. Several other ingredients in coffee also have anti-inflammatory properties that could have positive effects.”
Researchers say it is still unclear exactly how coffee lowers the risk. One explanation could be that caffeine blocks adenosine, a natural chemical that can trigger A-Fib. Another is that coffee’s antioxidant compounds, such as chlorogenic acids and melanoidins, provide heart-protective benefits.
“Coffee increases physical activity which is known to reduce atrial fibrillation,” Marcus added.
Atrial fibrillation affects more than 10 million U.S. adults. The condition is becoming more common as the population ages. It can cause fatigue, dizziness, and chest discomfort. It also increases the risk of stroke and heart failure.
Dr. Rod Passman of Northwestern University, who was not involved in the research, said the findings challenge old assumptions. “This is an important study that calls into question the lifestyle advice that we often give patients without clearly supportive data,” Passman told Healthline.
Experts caution that moderation remains key. The study only tested moderate coffee intake, about one cup per day. It did not examine other caffeine sources such as energy drinks, supplements, or pills. Those often contain far higher doses.
“People should absolutely not extrapolate from this study that more caffeine is therefore better,” Marcus said.
Alyssa Kwan, a clinical dietitian at Stanford Medicine, also warned against high-sugar or high-fat coffee drinks. “I would still caution against choosing coffee that might contain high amounts of added sugars or saturated fat, including items like lattes and mochas,” she told Healthline.
The takeaway from the DECAF study is that coffee, in moderation, is likely safe for most people with A-Fib. It might even help protect their hearts. Marcus said, “For people that enjoy drinking caffeinated coffee, they should not avoid it for fear that it’s going to worsen their atrial fibrillation.”