According to a study published in the New England Journal of Medicine, people who consume coffee may live longer than their non-coffee drinking peers. The drink is undeniably delicious, and it provides that morning dose of caffeine so many of us have come to depend on. But we haven't the foggiest idea whether or not coffee actually enables us to live longer.
As the researchers point out, it's impossible to tell if the relationship between coffee and mortality is "a causal or associational finding...." The participants (229,119 men and 173,141 women, ages 50 to 71) reported their coffee drinking habits at the beginning of the study and were then followed between 1995 and 2008 to see who among them died. After adjusting for alcohol consumption, smoking, and exercise habits, participants who drank the most coffee had a lower risk of premature death. In short, this is an observational study which relied on self-reported data. And the problems with studies of this kind are well known.
Even if the association is valid and coffee does prevent early death, researchers have no way of knowing what it is that makes the drink so beneficial. There are a variety of compounds in coffee that could provide some protective effect against different diseases, but the researchers didn't look at those.
Additionally, the type of coffee and how it's prepared changes the compounds the drink contains, which can impact how healthy coffee may be.
The drink could even help us fall in love and boost the global economy. But at this point, we just don't know exactly how coffee impacts our health. It's probably beneficial in some way and it probably isn't harmful. So, drink coffee because it's good, but don't treat it like it's a health miracle.