Oh Science, why have you forsaken me? In what is generally a reliable green light to consume as much coffee as you damn well please, today’s science news has turned its back on us all. A new study lead by Vanderbilt University PhD student Jingjing Zhu finds that drinking two or more cups of coffee a day may come with an increased risk of lung cancer.
Before we go any further, let me just stop and say that no, it’s not because coffee drinkers are more likely to pair their cuppa with a cigarette; the study took that into account. And it’s not even because these bean teens are freebasing coffee, though I’d guess the study didn’t quite give that particular hypothesis its due. Now that we’ve eliminating the two most likely culprits we can move on.
According to Live Science, Zhu et al’s findings were presented at the annual conference for the American Association for Cancer Research on March 31st. For the meta-study, the “international group of researchers” led by Zhu analyzed data from 17 different studies with a sum total of 1.2 million participants in the United States and Asia who were tracked for an average of 8.6 years. In each of the studies, participants were asked if they smoked, if they consumed coffee or tea, and how much. Per Live Science, about half were non-smokers.
Over the course of the studies, a total of 20,500 participants that developed lung cancer. Cross-referencing those participants with their coffee and tea drinking habits, the meta-study found that coffee drinkers had a 41% higher chance of developing the disease, with tea also having a 37% higher risk.
And while these finding seem to point to caffeine—the most obvious commonality between coffee and tea—as the carcinogenic agent, the meta-study found that in fact decaf coffee was associated with a 15% higher risk than that of regular coffee.
But we coffee drinkers still have outs. As an observational study, Zhu et al’s findings don’t prove any causal relationship between coffee consumption and an increased risk in lung cancer. Additionally, due to the way to studies were performed, the reliability of their data may be in question; participants were only asked about their smoking and coffee/tea habits at the beginning of the surveys, leaving open the possibility of changes in habits over the course of the average 8.6 years.
Secondhand smoke may also be an untracked factor in the findings. Coffee drinkers, it would seem, spend more time at coffee shops, places where smokers are more likely to congregate (and depending on where and when these studies took place, smoking may have even been allowed inside these businesses). Because of this, it could be the case that the additional exposure to secondhand smoke may be the leading factor; one’s love of coffee merely led to this increased exposure.
But as with most of the coffee-based studies, more research needs to be done before any hard conclusions can be drawn. So don’t go changing your coffee habits or become some weird flat-earth science denier just yet. There’s still time for Science to get this error straightened out.