No, drinking coffee won't save your life or prevent heart attacks

By Larry Husten - Contributor

Forbes

March 3, 2015

Once again the media has swallowed the bait hook, line, and sinker. Following the publication of a  a new study in the journal Heart last night, hundreds of news reports have now appeared extolling the miraculous benefits of coffee. Here’s just one typical headline from the Los Angeles Times: “Another reason to drink coffee: It’s good for your heart, study says.”

But a careful look at the study and previous research on coffee makes clear that this type of reporting is completely unwarranted. As I’ve written previously, the media loves to jump on studies like this and inform the public that, say, intense running is as bad as being sedentary. These sort of upbeat, highly positive stories making simple recommendations based on observational studies that are in no way capable of proving cause and effect are dangerous. Unfortunately, the journalists often receive support  from study authors and the journal editors and PR people who encourage  this gross misinterpretation and don’t take steps to refute these dangerous misconceptions.

First let’s take a closer looks at the actual study and its context. The relationship of coffee and cardiovascular disease has been difficult to assess. Although early studies found a possible increased risk associated with heavy coffee consumption, more recent studies have found the opposite. (Note the important word “associated.”) Now a new study published in Heart finds that people who consume moderate amounts of coffee may be less likely to have atherosclerosis.

The new study looked at more than 25,000 people in South Korea without known cardiovascular disease. Researchers examined the relationship between various levels of coffee consumption and the coronary artery calcium (CAC) score as measured by a multidetector CT scan. (CAC is often used as a measure of clogging of the heart’s arteries. It is by no means a perfect test but let’s leave that story for another day.) The researchers found that people who drank coffee were less likely to have calcium in their coronary arteries than nondrinkers. They described the relationship as U-shaped, with the lowest levels occurring in the people who drank 3 or 4 cups of coffee each day. The overall pattern remained present after multiple analyses adjusting for risk factors.

Interpreting Observational Studies

Most scientists, I hope, understand the limitations of an observational study like this. Although the researchers attempted to adjust for important differences between the groups, this effort is ultimately impossible when studies deal with real people in the real world and not mice living in cages. I would be willing to bet a whole lot of money that people who drink different amounts of coffee differ in all sorts of extremely important ways (psychological, physical, environmental, social). There is no way to measure or adjust for most of these factors. Coffee– along with alcohol, exercise, diet, and so many other “lifestyle” factors– is how we define ourselves.

Unlike the media, in this case the researchers were reasonably cautious in their conclusions. “Our findings are consistent with a recent body of literature showing that moderate coffee consumption may be inversely associated with cardiovascular events,” the authors wrote. But they concluded that “further research is warranted to confirm our findings and establish the biological basis of coffee’s potential preventive effects on coronary artery disease.”

Despite the recent positive findings, the senior author of the study, Eliseo Gualiar, an epidemiologist at Johns Hopkins, said in an email that he was “concerned that the role of coffee in preventing cardiovascular disease is exaggerated. Our study was an observational association study that by itself cannot prove causation.” However, Gualiar said the findings were “reassuring, in the sense that coffee intake, a very common habit, is not associated with increased cardiovascular risk.” Moderate coffee drinkers, he said, “should not be concerned that coffee is increasing their risk of cardiovascular disease. On the other hand, we believe that at this point we should still not recommend drinking coffee for preventing cardiovascular disease.”

Yale University cardiologist Harlan Krumholz said he agreed with Gualiar: “It is important that the public interpret this study in that context. People should not feel an imperative to drink coffee to lower risk, but those who enjoy coffee may take comfort in a study that failed to identify a risk and even suggested a benefit.”

Gualiar’s perspective was also largely endorsed by another expert not involved with the study, Thomas Whayne Jr., a cardiologist at the University of Kentucky, who disclosed that he is “a major fan of coffee as my favorite beverage.” “The bottom line,” he says, “is that, for the patient who loves coffee in moderation, there should be no restriction to moderate intake even in the severe heart-failure patient, and patients should be encouraged to enjoy coffee unless there were to be an unpleasant association with something such as increased arrhythmias.” Whayne said that cardiologists “should not recommend coffee, even in moderation, to prevent coronary atherosclerosis” but that they can reassure patients that there may be some benefit and, at worst, very little cardiovascular risk.”

These interpretations by the study authors and other experts strike me as completely reasonable. This is the way epidemiological evidence should be used. But these subtleties and nuances got lost in the mainstream media.

So what went wrong? I think the blame in this case starts with the PR machinery of the journal Heart, which is part of the BMJ (British Medical Journal) group. Here is the headline and subhead for this paper:

Moderate coffee consumption lessens risk of clogged arteries and heart attacks

People consuming three to five cups of coffee a day have lowest risk of clogging

It seems clear that this sort of headline is an invitation to distortion and exaggeration. I would propose that when publishing epidemiology studies journals and editors be extremely cautious and pro-active in press releases. Undoubtedly the media will continue to make mistakes, but there’s no reason why the medical establishment should be enabling these mistakes.