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Where Did the 8 Glasses of Water A Day Myth Come From?

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By Chris Gayomali

We have all been told at some point that proper hydration requires us to consume eight glasses of water a day. That works out to about two liters, which is an awful lot of fluid, considering the average human stomach (when unexpanded) is about the size of a balled fist.

But health researchers have refuted the eight-glasses-a-day claim as a silly myth riding a wave of flimsy scientific literature. In fact, many of the groups behind the public push for over-hydration have been exposed as having — surprise! — monetary interests in the fluid industry.

For example: In a 2011 article published in the British Medical Journal, Margaret McCartney debunked the eight glasses a day myth and noted that one water advocacy group in Europe, Hydration for Health, is not only sponsored by, but was actually created by food giant Danone. Under the company's expansive culinary umbrella? Volvic, Evian, and Badoit bottled waters.

Set aside the entangled interests of Big Bottled Water, and you'll see that study after study continues to show that the human body is remarkably resilient when it comes to quenching our thirst. Saharan nomads, for example, are capable of subsisting on very little water for days at a time in one of Earth's most hellish climates, as was first noted in 1976 by anthropologist Claude Paque.

You and I, on the other hand, may get a bit cranky in our air-conditioned offices if we forget to visit the water cooler for a morning, but it's highly, highly, highly improbable that we'd shrivel and die at the dusty hands of the dehydration monster. Consider all the other stuff we consume. Despite the widely held notion that tea and coffee dehydrate us, they actually count toward our overall water intake, says Dr. Stanley Goldfarb, a nephrologist (kidney researcher) at the University of Pennsylvania. Even though we're told it's important to drink eight glasses of water a day, "there's no evidence that benefits health in any real way and it really represents an urban myth," says Goldfarb. Even something like, say, a baked potato, is 75 percent water.

So where exactly did this eight glasses of water a day voodoo come from? The very idea of a "minimal water requirement" is actually a fairly recent notion that first appeared in dietary guidelines published in 1945 by the Food and Nutrition Board of the National Academy of Sciences. The academy spuriously suggested that "2,500 mL [2.5 liter] of fluid should be ingested on a daily basis," although a primary clinical study was never actually cited.

The idea may have been at least partly put forth by Frederick J. Stare, an influential 20th century nutritionist and founding chairman of the department of nutrition at the Harvard School of Public Health. (He passed away in 2002 at age 91.) Stare was one of the first to recommend that humans consume six or so 12-ounce glasses of water a day.

Since then, researchers have begun to see eight glasses a day as an overestimate (especially considering our diets), but there are still advocates pushing for eight glasses of pure water or more. Those proponents include Dr. Fereydoon Batmanghelidi, a medical practitioner in Virginia who claims that a lack of water is responsible for many preventable diseases. Water, after all, is still good for us. Recent studies have suggested that adequate hydration may not only give our cognition a boost, but goes a long way toward keeping chronic kidney disease at bay.

As for how much we should be drinking, there is unfortunately no hard and fast rule. (Sorry!) And when you include all the other stuff we munch on or guzzle throughout the day, we actually consume more than the recommended two liters. A 1995 Australian survey found that the diet of average adults provides more than enough daily fluid: Women take in about 2.8 liters a day, and men consume 3.4 liters a day.

Research suggests that drinking water when you start to feel thirsty is sufficient should you desire to continue existing. Clearly, it's all relative, as when you feel thirsty will be different if you're drenching yourself in spin class or spinning in your cushy chair at work. As with most things, it's probably best to listen to your body before proceeding accordingly.

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Big Questions
What is Duck Sauce?
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A plate of Chinese takeout with egg rolls and duck sauce
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We know that our favorite Chinese takeout is not really authentically Chinese, but more of an Americanized series of menu options very loosely derived from overseas inspiration. (Chinese citizens probably wouldn’t recognize chop suey or orange-glazed chicken, and fortune cookies are of Japanese origin.) It would also be unusual for "real" Chinese meals to be accompanied by a generous amount of sauce packets.

Here in the U.S., these condiments are a staple of Chinese takeout. But one in particular—“duck sauce”—doesn’t really offer a lot of information about itself. What exactly is it that we’re pouring over our egg rolls?

Smithsonian.com conducted a sauce-related investigation and made an interesting discovery, particularly if you’re not prone to sampling Chinese takeout when traveling cross-country. On the East Coast, duck sauce is similar to sweet-and-sour sauce, only fruitier; in New England, it’s brown, chunky, and served on tables; and on the West Coast, it’s almost unheard of.

While the name can describe different sauces, associating it with duck probably stems from the fact that the popular Chinese dish Peking duck is typically served with a soybean-based sauce. When dishes began to be imported to the States, the Americanization of the food involved creating a sweeter alternative using apricots that was dubbed duck sauce. (In New England, using applesauce and molasses was more common.)

But why isn’t it easily found on the West Coast? Many sauce companies are based in New York and were in operation after Chinese food had already gained a foothold in California. Attempts to expand didn’t go well, and so Chinese food aficionados will experience slightly different tastes depending on their geography. But regardless of where they are, or whether they're using the condiment as a dipping sauce for their egg rolls or a dressing for their duck, diners can rest assured that no ducks were harmed in the making of their duck sauce.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
Can You Really Go Blind Staring at a Solar Eclipse?
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A total solar eclipse will cut a path of totality across the United States on August 21, and eclipse mania is gripping the country. Should the wide-eyed and unprotected hazard a peek at this rare phenomenon?

NASA doesn't advise it. The truth is, a quick glance at a solar eclipse won't leave you blind. But you're not doing your peepers any favors. As NASA explains, even when 99 percent of the sun's surface is covered, the 1 percent that sneaks out around the edges is enough to damage the rod and cone cells in your retinas. As this light and radiation flood into the eye, the retina becomes trapped in a sort of solar cooker that scorches its tissue. And because your retinas don't have any pain receptors, your eyes have no way of warning you to stop.

The good news for astronomy enthusiasts is that there are ways to safely view a solar eclipse. A pair of NASA-approved eclipse glasses will block the retina-frying rays, but sunglasses or any other kind of smoked lenses cannot. (The editors at MrEclipse.com, an eclipse watchers' fan site, put shades in the "eye suicide" category.) NASA also suggests watching the eclipse indirectly through a pinhole projector, or through binoculars or a telescope fitted with special solar filters.

While it's safe to take a quick, unfiltered peek at the sun in the brief totality of a total solar eclipse, doing so during the partial phases—when the Moon is not completely covering the Sun—is much riskier.

WOULDN'T IT BE EASIER TO JUST TELL YOUR KIDS THEY WILL GO BLIND?

NASA's website tackled this question. Their short answer: that could ruin their lives.

"A student who heeds warnings from teachers and other authorities not to view the eclipse because of the danger to vision, and learns later that other students did see it safely, may feel cheated out of the experience. Having now learned that the authority figure was wrong on one occasion, how is this student going to react when other health-related advice about drugs, alcohol, AIDS, or smoking is given[?]"

This story was originally published in 2012.

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