That leaves the million dollar question: could this effect possibly be real? A 20-30% mortality reduction is a big deal; we joke about putting statins in the water supply, and yet are quite pleased when we find a 10% mortality reduction in a 6 year study on statin use in a high risk population. If there is no biological plausibility, the odds go way up that we have been seduced by confounders, bad methodology, or corrupt/inept investigators.

I have a few theories to offer in regard to biological plausibility. Well, every coffee drinker will have the same theory: coffee drinkers have more to live for! That might be said in jest, but there is something about starting each and every day with a beloved, relaxing ritual that might be very good indeed for that all-important balance between sympathetic and parasympathetic nervous system. This could sound woo-woo, but it’s not altogether crazy. After all, we have seen claims for mortality benefit of a similar magnitude made for warm-and-fuzzy practices like dog ownership. Malcolm Gladwell’s wonderful opening to Outliers reminds us of the possibility that age-old rituals might just outflank Pelotons and on-patent pharmaceuticals when it comes to longevity.

Then there’s the technical stuff. Yes, coffee contains polyphenols like chlorogenic acid with antioxidant properties that have been theoretically tied to health benefits like improving metabolic health and preventing Parkinson’s disease. Coffee drinking might favorably alter the gut biome. It might even improve liver health. Color me skeptical that these properties are so powerful that they could be the main driver in a 10% — or 30% — mortality benefit. They might, however, contribute, and could help explain the apparent dose-dependent response in which the 4 cup a day crowd outperforms the 1 cuppers.