Decades ago in the 70’s and 80’s there was a flurry of articles published in major medical journals that implicated coffee drinking as a risk factor for heart attacks. It was reported that the risk was related to the amount of coffee consumed: the more coffee, the higher the risk. But as research techniques improved, and better studies were performed, we were able to take a closer look at the findings. It turned out that it was not the coffee that was causing the bad effects, but that those people drinking coffee were more likely to smoke, do less activity (click to learn how exercise can save your life!), be overweight and live a generally less healthy lifestyle. All of these, of course, being risk factors for heart disease. When we performed better studies, that were more appropriately designed, and took these risk factors into account, it turned out that coffee had no such harmful effect, and that coffee may even have a favorable effect on the cardiovascular system, possibly even reducing cardiac risk. So have the benefits of coffee been underestimated?
So why is it that each week in the press we see articles about coffee that seem to contradict the findings from the week before? Hundreds of studies have been done to examine the effect of coffee on health, some terribly designed, some well designed, but of course newspapers don’t take that into account, they just publish whatever is likely to attract readers, without taking responsibility for the quality of the source of the news (an example of poorly interpreted journalism). So what are we to believe? The best way to settle the issue is to take a population of people, randomly assign them into two groups where one drinks coffee daily and one doesn’t, follow them for several years, and see what happens – this is what we call a randomized trial. The fact is though, that study is never going to happen, as it would be far too hard to arrange, and even harder to convince coffee drinkers to stop drinking coffee if they were put in the no coffee group!
So instead lets do the next best thing, choose decent studies from reputable medical journals and look at the effect that coffee had on the cardiovascular health of people who were followed in studies where coffee drinking habits of participants were recorded. After reviewing the literature extensively, I have summarized below what I believe to be the major findings of the well-designed studies regarding the effect of coffee on risk factors for cardiovascular disease such as blood pressure, diabetes, and cholesterol as well as the effects of coffee drinking on stroke, coronary disease, and the risk of dying from heart disease.
Coffee and Cholesterol – Coffee contains ingredients that can raise cholesterol however the concentration of these ingredients depends on the way it is prepared, with boiled coffee having a higher concentration and filtered coffee having a lower concentration. This was nicely demonstrated in a review looking at several studies showing that drinking boiled coffee was associated with an increase in cholesterol, but that drinking filtered coffee resulted in no significant effect on cholesterol. It would seem reasonable to recommend that those who have trouble with controlling high cholesterol should try to drink filtered rather than boiled coffee.
Coffee and Blood Pressure – When people that don’t usually drink coffee have coffee, they have an almost immediate short-term increase in blood pressure, which is likely of no consequence to health. Coffee has essentially no effect on blood pressure in people that regularly drink coffee. One study showed that coffee has no effect on the development of high blood pressure even in those drinking 6 cups per day.
Coffee and Diabetes – Diabetes is well recognized as one of the major risk factors for heart disease. Several components of coffee have favourable effects on the way the body deals with blood sugar. A review of several studies looking at the effect of coffee on diabetes showed that coffee drinking was associated with a lowered risk of developing diabetes. Interestingly, the risk of diabetes was lowest in those drinking more than 6 cups per day, but even small amounts of coffee intake were associated with a decreased risk of developing diabetes.
Coffee and Stroke – A study that looked at and analyzed the results of several other studies demonstrated that coffee drinking was not associated with stroke, and moderate coffee consumption may even be slightly protective.
Coffee and Heart Rhythm Disturbances – Contrary to what may be widely believed, well-designed studies have shown that even high dose coffee is not associated with rhythm disorders. Once large study showed that those drinking 4 cups per day were less likely to develop arrhythmias, including inappropriate sinus tachycardia and atrial fibrillation with RVR.
Coffee and Coronary Artery Disease – At the beginning of this article I talked about two articles (A1, A2) that showed that coffee drinking was associated with increased risk of coronary artery disease and many old studies demonstrated this. It turns out that the reason for this association was not due to the coffee itself, but those that drank coffee were much more likely to have risk factors for heart disease such as smoking, alcohol use, weight (click to learn how to achieve fast, effective weight loss), and physical inactivity. After accounting for the effect of these risk factors and performing larger studies, it turned out that the risk of coronary heart disease was lower in regular coffee drinkers (link to study). Since that time, many studies have been published that demonstrate moderate coffee drinkers have a decreased long-term risk of heart disease.
Coffee and Dying from Heart Disease – Well designed studies that followed participants for at least several years and recorded coffee habits demonstrate that regular coffee consumption was associated with a lower risk of developing heart disease, and a lower risk of dying from heart disease.
No study is perfect, and results of studies should always be interpreted with a degree of caution, but reassuringly, numerous well-designed studies have shown that coffee confers no significant risk of heart disease, and that in fact it may even be protective. Most of these studies looked at coffee drunk in moderation (2-4 cups) and it would appear reasonable to recommend moderate coffee consumption as part of a healthy lifestyle.