The mighty brains who write books about why your brain is going to melt unless you follow their advice often share an amazing new insight my Mom was well aware of all her life: drink tap water. It's good for you,* full of essential minerals and trace elements. There's such a thing as too filtered.
On the other hand, if you want me to laugh at you, even if you have a Ph.D. and say you've got a five-year grant from the National Institutes of Health to study Alzheimer's disease and women's brains, just say this:
"Purified and distilled waters are just fluids," [she'd love the free mention] said. "There is nothing hydrating there."
Stop and let that sink in. Here, let me help: "...water...there is nothing hydrating there." I'm not a Ph.D. biologist, but I did all right in etymology, and when water has ceased to be hydrating, both studies are too broken to be of any further use.
Or, a-hem, it might just be pretentious nonsense to sell fad-nutrition books.
Drink your damned water. If you're the kind of idiot who drinks distilled water, take your vitamins and, you know, electrolytes -- or wise up and switch to tap water or the tastier water they get from taps elsewhere and bottle up as spring water.
* This presumes you don't live in Flint, Michigan, and that if you're on a well, you haven't dug it too close to your privy or a leaking tank of benzine, etc. Most city water and well water is clean and wholesome, or at least until TV ratings time, when they'll set it on fire and explain how it will kill you dead.
8 months ago