For decades, doctors have warned folks suffering from heart rhythm problems to avoid coffee, out of concern that a caffeine jolt might prompt a herky-jerky heartbeat.
But a large new study has found that most people can enjoy their morning joe or afternoon diet cola free from worry -- caffeine doesn't seem to increase most people's risk of arrhythmias.
"We see no evidence for this broad-based recommendation to avoid coffee or caffeine," said study co-author Dr. Gregory Marcus, associate chief of cardiology for research at the University of California, San Francisco. "There could be some individuals where caffeine is their trigger, but I think the growing evidence is those cases are actually quite rare."
In fact, results indicate that every additional cup of coffee a person drinks daily might lower their risk of arrhythmia by about 3% on average, according to the study published July 19 in JAMA Internal Medicine.
"The majority of people, even those with arrhythmias, should be able to enjoy their cup of coffee, and maybe there are some people for whom caffeine or coffee may actually help reduce their risk," Marcus said.
Coffee is one of the most widely consumed beverages worldwide, but its properties as a stimulant have prompted many doctors to warn heart patients against drinking java, Marcus said.
To see whether caffeine really can cause the heart to race or beat abnormally, Marcus and his colleagues analyzed data from more than 386,000 people participating in a long-term British health study.
Of that large group, about 17,000 developed a heart rhythm problem during an average follow-up of 4.5 years, researchers said.
All participants were asked about their coffee consumption when they entered the study. Researchers compared their response to their likelihood of developing an abnormal heart rhythm down the line.
The result: There was no link at all between caffeine and heart rhythm disturbances, even when researchers took into account genetic factors that might influence the way individuals metabolize caffeine.
"We could find no evidence on a population level that those who consumed more coffee or those exposed to more caffeine experienced a heightened risk for arrhythmias," Marcus said.
The study results show "there is absolutely some unsubstantiated dogma that coffee can cause arrhythmias," said Dr. Zachary Goldberger, an associate professor of cardiovascular medicine at the University of Wisconsin-Madison.
However, Goldberger cautioned against reading too much into what the study observed about caffeine's potential protective benefits, given that the effect was so small.
"I think the bottom line, based on these findings, is that coffee may not cause arrhythmias, but it doesn't necessarily protect against them either," said Goldberger, co-author of a commentary accompanying the study.
Further research is needed to suss out exactly how coffee affects the heart, and why it might protect against arrhythmias, Marcus said.
Coffee has anti-inflammatory effects, and it's well-known that inflammation can contribute to heart rhythm problems, Marcus said. It also might be that caffeine motivates some people to be more physically active, which reduces the risk of arrhythmia.
"We are probably not fully aware of the various mechanisms that may be relevant" to the relationship between caffeine and heart health, Marcus said.
Marcus said that he encourages his own heart rhythm patients to experiment with coffee.
"In many cases anecdotally, it doesn't make a difference," Marcus said. "For most, I have not found that it's an important trigger. They are very happy to receive this good news, especially those who enjoy coffee."
Both Marcus and Goldberger acknowledge there are probably some individuals who don't respond well to coffee, and their concerns should continue to be taken seriously.
"If a patient comes to clinic with palpitations, or symptoms of an arrhythmia, and asks whether caffeine or coffee plays a role, that is a personalized discussion," Goldberger said. "If a patient reports having palpitations that seem correlated with coffee or caffeinated beverages, these data don't give us the license to tell them not to try to limit coffee. But I think we could tell our patient that coffee doesn't place people at higher risk of heart rhythm disturbances."
The U.S. National Heart, Lung, and Blood Institute has more about arrhythmias.
SOURCES: Gregory Marcus, MD, associate chief, cardiology for research, University of California, San Francisco; Zachary Goldberger, MD, associate professor, cardiovascular medicine, University of Wisconsin-Madison; JAMA Internal Medicine, July 19, 2021