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“Drink At Least 8 Glasses Of Water A Day” -- Really?

We have always been puzzled by the modern mantra to drink all that water. In Deadly Harvest we point out that our Pleistocene ancestors could achieve water balance without drinking any water at all. Not surprising really; not much fun competing with lions, crocodiles and hyenas for a sip from a muddy, excrement-infested waterhole.

On the contrary, a high plant-food diet should provide all the liquid you need.

Now Heinz Valtin , MD. says[i] that the universal advice, which has made swigging water a national pastime, lacks scientific proof and is more urban myth than medical insight.

Valtin, a kidney specialist and author of renowned text­books on the kidney and water balance, reports no supporting evidence for "8 x 8" (an 8oz glass 8 times). He finds it, "difficult to believe that evolution left us with a chronic water deficit that needs to be compensated by forcing a high fluid intake."

The 8 x 8 rule is slavishly followed. Everywhere, people carry bottles of water, constantly sipping from them; it is acceptable to drink water anywhere, anytime. A pamphlet distributed at one southern California university even counsels its students to "carry a water bottle with you. Drink often while sitting in class..."

How did the obsession start? Is there any scientific evidence that supports the recommend­ation? Does the habit promote good health? Might it be harmful?

Valtin thinks the notion may have started when the Food and Nutrition Board recommended "1 milliliter of water for each calorie of food," (64 fl oz per day) BUT with the overlooked kicker: “most of this water is CONTAINED IN FOOD!”

He found no scientific studies in support of 8 x 8. Rather, studies strongly suggest that such large amounts are NOT needed. Furthermore caffeinated drinks, like tea, coffee and infusions can be counted toward the daily total. Many experiments demonstrate how well the human body can maintain proper water balance.

On the other hand, in exceptional conditions such as kidney stones, strenuous physical activity, long airplane flights or hot weather, a good fluid intake is needed.

Drinking too much water can even be dangerous. "Water intoxication" causes the body to lose essential electrolytes. It leads to mental confusion and even death. Marathon runners, Ecstasy-crazed teen­agers and ordinary misguided water guzzlers have died from it.

It is often stated that by the time people are thirsty, they are already dehydrated. On the contrary, thirst begins when the concentration of blood has risen by less than two percent, whereas dehydration begins when that concentration has risen by at least five percent.

The warning that dark urine reflects dehydration is alarmist and false in most instances. Valtin argues that the burden of proof that everyone needs 8 x 8 should fall on those who persist in advocating the high fluid intake without, apparently, citing any scientific support.

Our view? Perrier, in a remarkable, 1980’s marketing coup, persuaded people to PAY for bottled drinking water instead of getting it out of a tap for free!

The bottled water industry has happily kept the “8 x 8” misunderstanding going – to the greater health of their balance sheets.  

[1] American Journal of Physiology, August 8, 2002

Extracted from The Natural Eating Newsletter, September 2002