Today I learned that the accepted wisdom of drinking eight glasses of water a day, including the accompanying reminder that beverages containing caffeine and alcohol do not count, is not supported by ANY scientific proof. In fact, such large amounts are not needed and can even be harmful (e.g., water intoxication, over 300 pollutants in tap water).

(Picks up a beer...) Cheers!

It has become accepted wisdom: "Drink at least eight glasses of water a day!" Not necessarily, says DMS physician Heinz Valtin, MD. The universal advice that has made guzzling water a national pastime is more urban myth than medical dogma and appears to lack scientific proof, he found.

In an invited review published online by the American Journal of Physiology August 8, Valtin, the Vail and Hampers professor emeritus of physiology at Dartmouth Medical School, reports no supporting evidence to back this popular counsel, commonly known as "8 x 8" (for eight, eight-ounce glasses)...

Valtin thinks the notion may have started when the Food and Nutrition Board of the National Research Council recommended approximately "1 milliliter of water for each calorie of food," which would amount to roughly two to two-and-a-half quarts per day (64 to 80 ounces). Although in its next sentence, the Board stated "most of this quantity is contained in prepared foods," that last sentence may have been missed, so that the recommendation was erroneously interpreted as how much water one should drink each day.

He found no scientific studies in support of 8 x 8. Rather, surveys of fluid intake on healthy adults of both genders, published as peer-reviewed documents, strongly suggest that such large amounts are not needed. His conclusion is supported by published studies showing that caffeinated drinks, such as most coffee, tea and soft drinks, may indeed be counted toward the daily total. He also points to the quantity of published experiments that attest to the capability of the human body for maintaining proper water balance...

Other claims discredited by scientific evidence that Valtin discusses include:

• Thirst Is Too Late. 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 (an accurate indicator of our state of hydration) has risen by less than two percent, whereas most experts would define dehydration as beginning when that concentration has risen by at least five percent

• Dark Urine Means Dehydration. At normal urinary volume and color, the concentration of the blood is within the normal range and nowhere near the values that are seen in meaningful dehydration. Therefore, the warning that dark urine reflects dehydration is alarmist and false in most instances.

"Drink at Least 8 Glasses of Water a Day" - Really? Dartmouth Professor Finds No Scientific Evidence for '8 x 8'

(You can find the complete scientific study at the American Journal of Physiology)

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Original posting by Braincrave Second Life staff on Jul 5, 2011 at http://www.braincrave.com/viewblog.php?id=593