I'm almost certain the "8 glasses" is BS, too. I made a concerted effort to follow that rule for about a year straight and felt NO difference whatsoever. I will say, I have also experienced he other end of the spectrum, in that, I have been gravely de-hydrated. This IS or at least can be a serious condition, so in the end, I'd actually say, if I had to choose between the two, I suppose I would rather have too much than too little! But like with anything: moderation is key.