They mention this in the article, but bears repeating - if you don't want to get a kidney stone (and believe me, you don't) 8 glasses a day is probably not a bad idea.
^ This. I have had kidney sand which bothered me a lot (because of stomach aching), until a doctor said that I should drink more water. I haven't had any problems since.
Bingo; in the middle of perhaps the highest stress period of my life I got sloppy about making sure I drank enough water and got a kidney stone or two as a reward. So I say:
No, You Do Not Have to Drink 8 Glasses of Water a Day. You Also Don't Have to Get Kidney Stones.
> if you don't want to get a kidney stone (and believe me, you don't)
To put some perspective on that, I recently had one and it was the worst pain in my life. I asked some women who have had both a stone and a natural childbirth which was worse, and they said the pain is about the same.
The difference is that at least you know +/- about a month when you're going to have a child and can prepare; with the stone, you're just suddenly in excruciating pain.