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, stated that, “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 and 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), 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.
Mittleman, who is also an Associate Professor of Medicine at Harvard Medical School and director of BIDMC’s cardiovascular epidemiological research program, mentioned that, 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.”
Mostofsky said, “The data in this study did not allow the researchers to look at differences in coffee strength, nor to compare caffeinated against decaffeinated coffee, which clearly needs to be looked at.”
“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.
This study 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.
“Habitual Coffee Consumption and Risk of Heart Failure: A Dose-Response Meta-Analysis”; Elizabeth Mostofsky, Megan S. Rice, Emily B. Levitan, and Murray A. Mittleman; Circ Heart Fail. published online before print 26 June 2012; DOI:10.1161/CIRCHEARTFAILURE.112.967299;