When did [the "8 glasses of water a day" myth] get started and how? Seems like for the past 7 years, [my] friends started talking about it.
But, just before that, bottled water became a trend to carry around. Please tell me it wasn't the bottle water companies who started this! You're suggesting, "drink water when you're thirsty" sounds unique, but hey, that's how I grew up.
-- "R from Ohio" (via the blog)
Dr. Heinz Valtin of Dartmouth's Medical School -- a kidney and water balance expert -- had that same question back in 2002 and decided to do a little investigating.
His conclusion? You can partially blame the Food and Nutrition Board of the National Research Council for starting this trend.
In a report, they recommended people take in a milliliter of water per calorie of food. If we apply that to a daily intake of 2,000 calories a day, we get two liters (or eight eight-ounce glasses) of water.
Why just partial blame? Well, that same recommendation also read, "most of this quantitiy is contained in prepared foods."
Pardon the cliche, but blame the media for spreading incorrect information. The water bottle, companies, of course, remained mum on the gaffe. Thus, here we are in the era of Vitamin/Smart/Protein water (some of which have almost as much sugar as a can of soda!)
This is not to say you shouldn't drink water. However, it should be a matter of drinking when you are thirsty (whether that adds up to four or nine glasses a day), not "because it's good for you."