"The association between caffeine and heart failure risk reduction was surprising," admitted study senior author Dr. David Kao. "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."
However, "the consistent relationship between increasing caffeine consumption and decreasing heart failure risk turns that assumption on its head," said Kao, who is assistant professor of cardiology and medical director at the Colorado Center for Personalized Medicine at the University of Colorado School of Medicine. His team published their findings Feb. 9 in the journal Circulation: Heart Failure.
Still, the findings can't prove cause and effect, and they also don't mean that coffee is any substitute for healthy living when it comes to your heart, 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," he said in a journal news release.
In their study, Kao and his colleagues analyzed data from more than 21,000 U.S. adults who took part in three major studies: the Framingham Heart Study, the Atherosclerosis Risk in Communities Study and the Cardiovascular Health Study. Participants were followed for at least 10 years.
In all three studies, drinking one or more cups of caffeinated coffee a day was associated with decreased long-term risk of heart failure.
In the Framingham Heart and the Cardiovascular Health studies, the risk of heart failure fell by 5%-12% per cup of coffee each day, compared with having no coffee.
The Atherosclerosis Risk in Communities Study found that the risk of heart failure didn't change with 0 to 1 cup of coffee per day, but was about 30% lower in people who had at least 2 cups a day.
The findings for decaffeinated coffee were different. The Cardiovascular Health Study found no link between decaf and heart failure risk, while the Framingham Heart Study found that decaf was associated with a significantly higher risk of heart failure.
Further analysis showed that caffeine from any source appeared to be associated with decreased heart failure risk, and that caffeine played at least some role in coffee's apparent heart benefit, according to the authors.
"While unable to prove causality, it is intriguing that these three studies suggest that drinking coffee is associated with a decreased risk of heart failure and that coffee can be part of a healthy dietary pattern if consumed plain, without added sugar and high fat dairy products such as cream," said Penny Kris-Etherton, immediate past chairperson of the American Heart Association's Lifestyle and Cardiometabolic Health Council Leadership Committee.
"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/nonfat dairy products, and that also is low in sodium, saturated fat and added sugars," Kris-Etherton advised in the release.
"Also, it is important to be mindful that caffeine is a stimulant and consuming too much may be problematic -- causing jitteriness and sleep problems," she added.
Two other heart specialists -- both unconnected to the new study -- weighed in on the findings.
Dr. Michael Goyfman directs clinical cardiology at Long Island Jewish Forest Hills in New York City. He said the study had a few flaws.
"Coffee intake was self-reported, and thus prone to many inaccuracies," Goyfman noted. "Furthermore, the amount of coffee was not standardized. Does one cup mean 8 ounces of coffee, or 20 ounces?"
He pointed out that prior studies have shown that too much coffee was tied to a "stiffening" of a key part of the heart's aorta. On the other hand, numerous studies have shown that America's favorite morning brew appears linked to a lowered odds for Parkinson's disease.
So, "until further studies are performed to directly address this question, I would recommend for patients to use common sense with respect to their coffee consumption and to consult with their physician regarding specific intake limits," Goyfman said.
Dr. Guy Mintz directs cardiovascular health at Northwell Health's Sandra Atlas Bass Heart Hospital in Manhasset, N.Y.
He largely agreed with Goyfman, saying the new findings show "an interesting association" but are not strong enough to warrant any recommendation to support upping your coffee intake.
Mintz noted that there are different types of heart failure, so "what type of heart failure does caffeine affect?" he asked.
"Caffeinated coffee in moderation can be part of a heart healthy diet without deleterious effects," he said, but beyond that, the new study is merely "a starting point" for further investigation.
"Patients who do not drink coffee should not start," Mintz believes, "and patients should certainly not start consuming supplements with caffeine such as 5-Hour Energy or Red Bull, etc., to reduce their risk of heart failure."
In the meantime, he said, "the research and the story need to continue."
The U.S. National Heart, Lung, and Blood Institute offers a guide to a healthy heart.
SOURCES: Michael Goyfman, MD, director, clinical cardiology, Long Island Jewish Forest Hills, New York City; Guy L. Mintz, MD, director, cardiovascular health and lipidology, Northwell Health's Sandra Atlas Bass Heart Hospital, Manhasset, N.Y.; Circulation: Heart Failure, news release, Feb. 9, 2021