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Drinking one or more cups of coffee a day may reduce the risk of heart failure, according to new research. But only if it's caffeinated.

The analysis of data from three large, well-known heart disease trials was published Tuesday in the ľ¹ÏÖ±²¥ journal . It found the more coffee people drank, the lower their risk for heart failure. But that benefit didn't extend to people who drank decaf.

"The association between caffeine and heart failure risk reduction was surprising," senior author Dr. David Kao said in a news release. Kao is an assistant professor of cardiology and medical director at the Colorado Center for Personalized Medicine at the University of Colorado School of Medicine in Aurora.

"Coffee and caffeine are often considered by the general population to be 'bad' for the heart because people associate them with palpitations, high blood pressure, etc.," he said. "The consistent relationship between increasing caffeine consumption and decreasing heart failure risk turns that assumption on its head."

But don't reach for a refill just yet, Kao said. "There is not yet enough clear evidence to recommend increasing coffee consumption to decrease risk of heart disease with the same strength and certainty as stopping smoking, losing weight or exercising."

Using the AHA's Precision Medicine Platform, which gives researchers tools and access to diverse datasets, Kao and his team analyzed information from the Framingham Heart Study, the Atherosclerosis Risk in Communities Study and the Cardiovascular Health Study. Collectively, these studies included 10 years of follow-up for more than 21,000 adults who drank up to three cups of coffee per day.

Across all three studies, people who drank more coffee had a lower long-term risk of heart failure.

Among those in the Framingham and Cardiovascular Health studies, the risk of heart failure fell by 5%-12% per cup of coffee per day, compared to people who drank no coffee. For those in the Atherosclerosis Risk in Communities Study, there was no change in heart failure risk for people who drank one cup of coffee per day, but a 30% lower risk for those drank two cups or more. Drinking decaf, on the other hand, significantly increased the risk of heart failure for those in the Framingham study, while having no impact on those in the Cardiovascular Health Study.

The studies did not distinguish between coffee prepared by different methods (percolated, drip, French press or espresso), where the beans came from or how strong the coffee was. And while they attributed the reduction in heart failure risk to caffeine consumption, the researchers did not address whether these findings might apply to other caffeinated drinks, such as energy drinks, caffeinated teas, soda or other substances.

Federal dietary guidelines say three to five 8-ounce cups a day of plain, black coffee can be part of a healthy diet. But popular, coffee-based drinks – such as lattes and macchiatos – can be high in calories, added sugar and fat. Also, despite its benefits, research shows caffeine can be dangerous when consumed in large amounts. The American Academy of Pediatrics cautions it should not be given to children.

Penny Kris-Etherton, a distinguished professor of nutrition at the Pennsylvania State University College of Health and Human Development in University Park, cautioned against consuming excessive amounts of coffee.

"The bottom line: enjoy coffee in moderation as part of an overall heart-healthy dietary pattern that meets recommendations for fruits and vegetables, whole grains, low-fat/non-fat dairy products, and that also is low in sodium, saturated fat and added sugars," she said in the release. Kris-Etherton was not involved in the new research. "Also, it is important to be mindful that caffeine is a stimulant and consuming too much may be problematic – causing jitteriness and sleep problems."

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