Water and epistemology
According to the latest Scientific American podcast, there is no scientific evidence to back up the common belief that everyone should drink eight glasses of water per day. Nor is there scientific evidence to back up many of the claimed benefits of increased water consumption: improved skin, better regulated appetite, etc.
However, the podcast equates “no scientific evidence” with “not true.” The title of the podcast is The Mythical Daily Water Requirement. “Mythical” means “false.” (There are more nuanced uses of the word “myth,” but I don’t think they are relevant here.)
It has been known for some time that the eight-glass-a-day recommendation is not well substantiated by experiments. That’s not to say increased water consumption isn’t beneficial. After all, there have not been any randomized trials to prove that parachutes improve your chances of survival when jumping from an airplane either.
Randomized trials are not the only way to learn about the world, and are not as effective as commonly believed. Most published research findings are false. Randomized trials are a tool for exploring reality, sometimes the best tool for a particular task, but not the only tool.
It’s plausible that drinking eight glasses of water per day is beneficial, or at least harmless, based on anecdotal evidence. Certainly drinking too little water is fatal (though there have been no randomized trials to confirm this!) and so it is reasonable to presume there is some curve showing increased benefit with increased water intake, up to a point. The curve would go back down at some point, as it is possible to drink too much water. It would be interesting to see randomized studies to explore where the curve flattens out, exploring consumption levels safely between the harmful extremes.
Tags: Biostatistics, Science
