Can drinking water prevent dehydration?
Before you laugh at the ridiculousness of such question, let me tell you that European Union bureaucrats in Brussels conducted a thorough three-year investigation, and found that there's no evidence to prove that claim:
Producers of bottled water are now forbidden by law from making the claim and will face a two-year jail sentence if they defy the edict, which comes into force in the UK next month.
Oh, Europe. Link - via Metafilter
Similarly, most foods and beverages contain fluids to a greater or lesser extent and can be used to prevent dehydration. You probably never need to drink water.
That would have pleased W.C. Fields a great deal.
So, it's not just the USA.
The first link in the "related articles" is this: http://www.telegraph.co.uk/health/healthnews/8632375/Advice-to-drink-eight-glasses-of-water-daily-nonsense.html
So.. you make your mind up.
The difference between mineral bottled water and tap water is in the minerals, and not in the water…and sometimes bottled mineral water contains more pollution residues than tap water, which is controlled.
It's not really a control-freak-rule, it's more about contain lies in advertising !