We’ve all been subjected to the health admonition of drinking eight, eight-ounce glasses of water per day—known as 8×8. Humans, apparently, have evolved a chronic water deficit, and must constantly replenish their dessicated bodies with high volumes of fluid until their urine runs clear. Water is supposed to be good for your skin, your weight, your purity, and your brain—which is, afterall, 74% water.
Balderdash, says a new review of the scientific literature by kidney gurus Dan Negoianu and Stanley Goldfarb from the University of Pennsylvania. They found that for the average, healthy individual, there is no evidence that increased water intake benefits organ functioning, appetite, headaches, skin tone, or substance clearance from the kidneys—and the origin of 8×8 is a mystery. The human body didn’t evolve a chronic thirst—it evolved a great capacity for maintaining proper water balance in the face of variable intake.
These findings support an earlier study by Heinz Valtin from Dartmouth, which found no support for 8×8, and debunked a few other myths. He found that dark urine does not mean dehydration, caffeinated beverages “count” as fluid intake, thirst doesn’t mean “it’s too late,” water doesn’t prevent (or help) constipation, cancer, or heart disease.
However, barring extreme cases (e.g. overcompensating marathon runners and Ecstasy users), excess water is pretty harmless (aside from the possible guilt at not achieving your health goal, polluting the environment with plastic bottles, and possibly swallowing some tranqs).
So what’s the origin of 8×8 evangelism? Valtin cites one speculation. In 1945, The Food and Nutrition Board of the National Research Council wrote that “an ordinary standard for diverse persons is 1 milliliter for each calorie of food,” which would amount to about 2–2.5 liters, or 64–80 ounces per day. But eager readers may have missed the following sentence, which noted that “most of this quantity is contained in prepared foods,” particularly fruits and vegetables, but even in meat, bread, and nuts. And thus was born our obsession with water.