As the mercury rises you'll hear it even more: Drink 8 glasses of water every day for optimal health. But where did this figure come from? Do we real need to drink this much, more, less?

Did a Government Panel Start the 8x8 Water Rule?

No one's really sure where the idea of needing 64 ounces of water daily originated. Heinz Valtin, a Dartmouth Medical School physician, thinks the recommendation may be derived from a 1945 U.S. National research Council Food and Nutrition Board report.

The authors recommended “1 milliliter of water for each calorie of food,” which would work out to 64 to 80 ounces for people eating between 1800 and 2400 calories. The 8 glasses recommendation may have taken hold because it's a nice round number (8 glasses x 8 ounces each = 64 ounces) .

Is Drinking 8x8 What NRC Really Said About Water?

Apparently lost in the translation of the Food and Nutrition Board report was its next sentence: “[M]ost of this quantity is contained in prepared foods.”

It's important to note that in 1945, the board was not talking about processed junk foods. Pasta contains water when prepared for dinner. In fact, most food contains some water with fruits and vegetables containing the most.

Water Content of Foods

Cucumbers, raw: 96%

Lettuce, head: 96%

Peppers, green: 94%

Watermelon: 93%

Bean sprouts: 92%

Eggplant, raw: 92%

Peaches, raw: 90%

Strawberries, raw: 90%

Apples: 85%

Apricots: 85%

Potatoes, raw: 85%

Oranges: 86%

Grapes: 82%

Chicken, boiled: 71%

Turkey, roasted: 62%

source: Survival Acres via. PsychCentral

Speros Tsindos of the department of dietetics and human nutrition at La Trobe University in Victoria, Australia says "Humans need to maintain fluid balance and need to drink water when required, but should also consider fluid in unprocessed fruits and vegetables and juices."

So, Do Caffeinated or Alcholic Beverages Really Count Against Your Fluid Balance?

Sources on hydration and caffeine typically suggest that alcohol or coffee, tea, and other caffeinated beverages should not be counted in your 8-glasses a day. This is nonsense according to Valtin.

"Valtin presented evidence that juice, milk, and even caffeinated beverages and beer—in moderation—can be sources of fluid intake. When these beverages are counted, Valtin says, the average daily intake for adult Americans is 1,700 milliliters, just shy of the 8x8 water-only target of 1,900 milliliters. And that average doesn't include the water content in fruits, vegetables, and other solid foods."

Drink Water For Health . . . When You Are Thirsty!

There are many, reasons to choose water to quench your thirst, but Valtin argues that meeting some 8-glass minimum quota is not one of them.