Another week, another coffee-is-good-for-you study that’s caught people’s attention. New research found a link between regular coffee consumption and a reduced risk of death. While the findings are the latest to suggest that coffee is perfectly fine to drink, they’re not necessarily strong proof that your daily cup of joe is life-saving.
The study was conducted by researchers at Southern Medical University in China and was published in the Annals of Internal Medicine. It looked at data from the UK Biobank, a long-running research project that’s been tracking the health of UK residents. As part of the project, people detailed their dietary habits, including their coffee consumption.
Compared to people who didn’t report drinking coffee, the researchers found, people who drank coffee (up to and above 4.5 cups a day) were less likely to die of any cause over a seven-year follow-up period. This pattern held true after accounting for other factors like a person’s lifestyle, and even when people reported drinking sugar-sweetened coffee.
“Moderate consumption of unsweetened and sugar-sweetened coffee was associated with lower risk for death,” the study authors wrote.
As Gizmodo has covered before, this is far from the first work to suggest that coffee is good for you. Other studies have found a link between coffee consumption and a lower risk of heart failure, liver damage, and indeed, even early death. Overall, these studies outnumber the ones that suggest coffee could harm health. So by this point, there’s not much debate left as to whether coffee is an “unhealthy” food, at least for the average person. (People with certain conditions, such as clinical anxiety, might want to avoid the stimulant effects of caffeine, though.)
All that said, it’s always tricky to study the benefits and harms of food, and nutrition scientists typically have to conduct research that comes with some major limitations. This study, the authors themselves note, only looked at people’s diets at a single moment of time. It’s possible that some people started or stopped drinking coffee after the start of the study. It’s also possible that people misremembered their typical diet, a well-known flaw in these kinds of surveys.
But perhaps the most important caveat is that correlation isn’t necessarily causation. Coffee-drinking people may be different from those who intentionally abstain. They might tend to exercise more or keep to a healthier diet, for instance. Scientists do try to adjust for these kinds of factors, but it’s often not possible to fully eliminate this sort of noise in the data.
Interestingly enough, the study didn’t find the same correlation for artificially sweetened coffee. That could mean that mixing your espresso with Splenda instead of a sugar packet makes the beverage less healthful, but it could also be an example of why these conclusions may not be quite as sturdy as the headlines make them look.
This kind of research, known as an observational study, is an important part of science. Often, we simply can’t run a gold-standard clinical trial to test out theories about the world. But we also shouldn’t take the numbers that any single study spits out as gospel (in this one, the associated risk of early death was up to 30% lower for coffee-drinkers). Given the bulk of the evidence, you can rest easy knowing that drinking coffee in moderation isn’t likely to cause you any harm. But any conclusion beyond that is murkier.
And honestly, who cares? I’m certainly not having my daily coffee because I think I’ll live longer as a result—I just like the taste and morning pep it gives me.