Scientific studies on coffee and health emerge daily from laboratories around the world. It’s typically good news, with more scientifically confirmed associations between coffee and disease-fighting properties. It’s a big switch from ten or fifteen years ago, when negative studies continued to feed the old myths that have long been disproven.
What changed, simply put, is that science got better. Refined methodologies enabled scientists to account for and separate out the effect of other risk factors, like smoking and poor cardiovascular fitness. As coffee was isolated out of the mix, it became increasingly clear that the myths had come from other sources, or “confounding factors” as they’re called.
But even scientists are not perfect, it seems, and old habits can creep in. One recent study appears to have gone retro, without the cachet the term has in style and fashion. The study by scientists at the University of South Carolina, published in the journal Mayo Clinic Proceedings, not only did not separate out typical confounding factors, but acknowledged their prevalence in the population they studied. In another departure from standard research protocol, they presented findings limited to a subgroup that was not previously identified for study. Instead, a subgroup was subsequently carved out because data, as applied to that group alone, could yield a reportable finding.
Out of Step
The study presented a finding of a 21% increase in mortality among subjects under 55 years of age who drank more than 28 cups of coffee a week. The research team confirmed, however, that the subjects were overweight or obese, had lower cardiovascular fitness levels, and tended to smoke. The scientists in fact stated that those who consumed higher amounts of coffee were more likely to smoke and had lower levels of cardiovascular fitness. They also state in the paper that, “The only marginally significant association of coffee consumption and all-cause mortality was observed in [overweight/obese] men … who consumed more than 28 cups of coffee per week.” No other group of coffee drinkers was at increased risk. The authors also state that “Smoking is likely to be one of the most important factors to cause residual confounding in this investigation.”
Not surprisingly, these findings are totally out of step with the vast preponderance of the scientific literature. Rather, the prevailing body of scientific evidence affirms that coffee is associated with a lower risk of dying at a young age. The largest-ever analysis of coffee and mortality found a clear connection between coffee consumption and a reduced risk of dying from any cause. The findings, published just last year, spanned all consumption levels among 400,000 women and men. Compared to men who drank no coffee, those who drank two to three cups of coffee each day has a 10% mortality reduction, while those who drank four to five cups daily had a 12% mortality reduction. In women, the mortality reductions were even more prominent, with those who drank two to three cups of coffee each day having a 13% mortality reduction, while those who drank four to five cups daily had a 16% mortality reduction. Such favorable mortality risk reductions held across all causes, as well as for specific causes including heart disease, respiratory disease, stroke and diabetes.
Additionally, a very recent meta-analysis assessed 23 independent studies and concluded that coffee drinkers are at a lower risk of mortality from all causes than people who do not drink coffee. A meta-analysis is a study that compiles data and subjects from multiple studies, and applies a fresh analysis to yield a wider and more comprehensive examination of the findings.
Interestingly, the news media covered the story with more than ample scepticism. Fifteen years ago, a study like this one would likely have sparked massive, negative media attention that drew upon the generally negative posture taken toward coffee and health. Instead, the tenor of the current coverage was notably even-handed, if not leaning positive. Typically, reporters zeroed in on the study’s methodological flaws and then segued quickly into the now well established findings linking coffee with significant health benefits.
Clearly, attitudes have changed along with scientific methodologies. What could have been a major media crisis around a scathing critique of coffee and caffeine instead turned out to be a nonstarter. Apparently, years of positive news about coffee and health had cultivated a widely accepted positive view of coffee.
Perhaps due to efforts set in motion by NCA with its 2003-07 Coffee Delivers! campaign, which took the emerging good news out of scientific journals and into public hands, audiences now appear to err on the side of coffee’s health benefits rather than proposed risks. Audiences appear now to view a negative study almost as a suspicious outlier rather than a mainsteam confirmation of bad news. The knee-jerk reaction appears now to support coffee rather than attack. Clearly, the ayes have it. And so does science.