New research from the US suggests drinking coffee in moderation, that is four European cups (equivalent to two 8-ounce American servings) per day, may protect slightly against heart failure, contradicting the guidelines of the American Heart Association that currently warn against regular coffee consumption.

You can read a paper on the study, by researchers at Beth Israel Deaconess Medical Center (BIDMC) and Harvard School of Public Health in Boston, in the 26 June issue of the journal Circulation Heart Failure.

Some previous studies have suggested there is a protective heart benefit from regular coffee consumption, while others have found no such link. So in this new study, the researchers decided to look at the data differently, and shift the debate from a question of “yes” or “no” to “how much”.

Lead author Elizabeth Mostofsky, a post-doctoral fellow in the cardiovascular epidemiological unit at BIDMC, told the press:

“Our results did show a possible benefit, but like with so many other things we consume, it really depends on how much coffee you drink.”

Mostofsky and colleagues analyzed data from five studies, four carried out in Sweden the other in Finland, and found a statistically significant J-shaped curve linking coffee consumption and heart failure risk (the lowest risk being at the bottom of the curve).

Altogether, the self-reported coffee consumption data came from 140,220 participants who experienced a total of 6,522 heart failure events.

The researchers found that compared with drinking no coffee at all (the start of the J-curve, on the left), participants who drank four European cups (or two 8-ounce American servings) per day had an 11% lower risk of heart failure (the bottom of the J-shaped curve).

This dose-response analysis showed that at higher levels of consumption this benefit gradually disappeared, until at five European cups, there was no benefit and at more than five cups a day, there may be potential for harm, compared to drinking no coffee at all (coinciding with where the right-hand side of the J-curve rises higher than the left).

The results showed no evidence that the link between coffee and heart failure risk varied by sex or by history of heart attack or diabetes.

Although Mostofsky and colleagues did not investigate why moderate coffee consumption appears to offer modest protection against heart failure, they speculate it could have something to do with how coffee consumption affects diabetes and high blood pressure, two of the biggest risk factors for heart failure.

Senior author Murray Mittleman, a physician at BIDMC’s Cardiovascular Institute, said:

“There is a good deal of research showing that drinking coffee lowers the risk for type 2 diabetes.”

“It stands to reason that if you lower the risk of diabetes, you also lower the risk of heart failure,” he added.

Another reason could be studies have consistently shown that light coffee and caffeine consumption raises blood pressure.

“But at that moderate range of consumption, people tend to develop a tolerance where drinking coffee does not pose a risk and may even be protective against elevated blood pressure,” said Mittleman, who is also an Associate Professor of Medicine at Harvard Medical School and director of BIDMC’s cardiovascular epidemiological research program.

The data in this study did not allow the researchers to look at differences in coffee strength, nor to compare caffeinated against decaffeinated coffee.

Mostofsky said it was clear this link needs further investigation:

“But in the short run, this data may warrant a change to the guidelines to reflect that coffee consumption, in moderation, may provide some protection from heart failure,” she urged.

The research revealed today follows a number of recent studies linking coffee consumption with health benefits. An observational study published in Archives of Internal Medicine in September 2011 suggested that coffee may lower the risk of depression in older females, whilst other research has suggested benefits related to skin cancer and endometrial cancer and diabetes. Two further studies have suggested that coffee may provide health benefits connected with the brain, in particular Alzheimer’s Disease and memory function.

Related reading: Drinking Coffee: More Good Than Harm? (9 July 2012)

Written by Catharine Paddock