I’m sure you’ve heard variations on the notion that we’re all effectively dehydrated and should drink more water … where “more” is defined as a minimum of 64 ounces of water. It’s pseudo-scientific bullshit, as you may have already decided for yourself:
If there is one health myth that will not die, it is this: You should drink eight glasses of water a day.
It’s just not true. There is no science behind it.
And yet every summer we are inundated with news media reports warning that dehydration is dangerous and also ubiquitous.
These reports work up a fear that otherwise healthy adults and children are walking around dehydrated, even that dehydration has reached epidemic proportions.
Let’s put these claims under scrutiny.
I was a co-author of a paper back in 2007 in the BMJ on medical myths. The first myth was that people should drink at least eight 8-ounce glasses of water a day. This paper got more media attention (even in The Times) than pretty much any other research I’ve ever done.
It made no difference. When, two years later, we published a book on medical myths that once again debunked the idea that we need eight glasses of water a day, I thought it would persuade people to stop worrying. I was wrong again.
Many people believe that the source of this myth was a 1945 Food and Nutrition Board recommendation that said people need about 2.5 liters of water a day. But they ignored the sentence that followed closely behind. It read, “Most of this quantity is contained in prepared foods.”
