Coffee ‘may reduce risk of heart attack’, data from three large studies suggests

Drinking between one and three cups of caffeinated coffee a day could reduce the risk of heart failure risk, according to new research based on three long-running heart disease studies examining the health outcomes of tens of thousands of people.

Coronary artery disease, heart failure and stroke are among the top causes of death worldwide, but scientists say the lifestyle elements which can lead to these serious conditions are not yet fully understood.

“While smoking, age and high blood pressure are among the most well-known heart disease risk factors, unidentified risk factors for heart disease remain," said David Kao, senior author of the study, and assistant professor of cardiology at the University of Colorado School of Medicine in Aurora, Colorado.

The scientists used three well-known heart disease studies to examine whether coffee intake had a correlation with mortality.

Through a “machine learning” method, the team examined data from the Framingham Heart Study, which began in 1948 with 5,209 adult subjects, and is now on its fourth generation of participants; the Atherosclerosis Risk in Communities Study, which began in 1985, and focuses on how particular heart conditions affect people of different age, sex, ethnicity, and location; and the Cardiovascular Health Study, which has looked at health outcomes of 5,000 people since it began in 1989.

Each study included at least 10 years of follow-up, and, collectively, the studies provided information on more than 21,000 US adult participants, the scientists said.

“The risks and benefits of drinking coffee have been topics of ongoing scientific interest due to the popularity and frequency of consumption worldwide,” said Professor Linda Van Horn, chief of the Department of Preventive Medicine's Nutrition Division at the Northwestern University Feinberg School of Medicine in Chicago. 

She added: “Studies reporting associations with outcomes remain relatively limited due to inconsistencies in diet assessment and analytical methodologies, as well as inherent problems with self-reported dietary intake.”

To analyse the outcomes of drinking caffeinated coffee, researchers categorised consumption as zero, one, two, or three or more cups a day.

Across the three studies, coffee consumption was self-reported, and no standard unit of measurement was available.

The analysis found in all three studies, those who reported drinking one or more cups of caffeinated coffee had an associated decreased long-term heart failure risk.

In the Framingham Heart and the Cardiovascular Health studies, the risk of heart failure over the course of decades decreased by 5 to 12 per cent for each cup of coffee per day, compared with no coffee consumption.

In the Atherosclerosis Risk in Communities Study, the risk of heart failure did not change between zero to one cup per day of coffee, but the researchers said it was about 30 per cent lower in people who drank at least two cups a day.

Drinking decaffeinated coffee appeared to have an opposite effect on heart failure risk - significantly increasing the risk of heart failure in the Framingham Heart Study. 

In the Cardiovascular Health Study however, there was no increase or decrease in risk of heart failure associated with drinking decaffeinated coffee. 

When the researchers examined this further, they found caffeine consumption from any source appeared to be associated with decreased heart failure risk, and caffeine was at least part of the reason for the apparent benefit from drinking more coffee.

“The association between caffeine and heart failure risk reduction was surprising,” Dr Kao said.

“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, etcetera.”

He said “the consistent relationship between increasing caffeine consumption and decreasing heart failure risk turns that assumption on its head”. 

But warned: “However, 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.”

According to US federal dietary guidelines, three to five 8-ounce cups of coffee per day can be part of a healthy diet, but that only refers to plain black coffee. 

The American Heart Association warns popular coffee-based drinks such as lattes and macchiatos are often high in calories, added sugar and fat. 

In addition, despite its benefits, research has shown that caffeine also can be dangerous if consumed in excess. Additionally, children should avoid caffeine. 

“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, professor of nutritional sciences at Pennsylvania State University.

She added: “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. 

“Also, it is important to be mindful that caffeine is a stimulant and consuming too much may be problematic - causing jitteriness and sleep problems.”

The researchers cautioned that some study limitations that may have impacted the results of the analysis. These included differences in the way coffee drinking was recorded, the type of coffee consumed, and the unit measurement for one cup.

The research is published in the journal Circulation: Heart Failure.