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Iron · #1 03-31-2007, 12:42 PM

Here's a post I've come up with about myths concerning water. It concerns a lot of widely held long time beliefs that I believe are false about water.

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I wrote it in response to one of perhaps thousands of articles purporting the alledged need for copious amounts of water and the almost magical properties water supposedly has--

There's hundred's of articles out there touting the "magical" properties of water, but none that back up their statements with any referenced scientific explanations. That's because it's become such "common knowledge" that to question it seems to go against everything we deem to be holy and it almost seems un-American to go against it. Most of this is pushed by bottled water companys that have found a gold mine in selling us water that's no better than we can get from our own tap.

There's absolutely no scientific evidence to support the well entrenched belief that we need this much water (8 glasses of 8 ounces a day) or that it does the things that a lot of articles purport.

For starters the idea that water "flushes out" anything is erroneous. It's not like the faster the water goes through you the more likely it is to pick up toxins like flushing dirt off the hood of a car. The body maintains a steady water level via the sodium/potassium electrolyte system. Excess water is simply excreted. Toxins, viruses or whatever do not adhere to water molecules anyway so they are uneffected by water. That's why you have an immune system. Water simply transports t-cells, macrophages et.al. and other components of the immune system to the toxins to destroy and/or eliminate them.

If you are deficient (dehydrated) than you need enough to replenish back to normal levels. Excesses don't help anything or speed up any processes. Excess water is asimilated through the duodenum and the rest of the colon goes into the blood and then the kidney's excrete all excess. The extra water never even makes it into the cells to do any good.

There's a lot of myth's concerning water consumption. The two biggest are:

1. That only water that is straight water is any good. Not true. Water is water as far as the body is concerned whether it's from tap, coffee or from a bannana.

2. Another myth is that everyone needs 8 glasses a day.

The origination of this recommendation of 8 glasses of water is hard to find. One idea says it comes from a mis-reading of an outdated 1945 National Research Council study that's explain a little later. Another idea is that it came from a World War 2 study trying to determine the amount of water a typical soldier had to have available for himself.

The following is a little long and I apologize for it. However, it should be enough to expunge some of the these commonly held myths:

Recommended Water Intake A Myth, Heinz Valtin, MD, DMS, et. al.

It has become accepted wisdom: "Drink at least eight glasses of water a day!" Not necessarily, says a 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, 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). The review will also appear in a later issue of the journal.

Valtin, a kidney specialist and author of two widely used textbooks on the kidney and water balance, sought to find the origin of this dictum and to examine the scientific evidence, if any, that might support it. He observes that we see the exhortation everywhere: from health writers, nutritionists, even physicians. Valtin doubts its validity. Indeed, 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 of the National Research Council in 1945 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.

A study on dieting does not show a significant improvement in weight loss resulting from more drinking. Likewise, constipation, sometimes thought to be alleviated by drinking, is not discernably impacted by an extra intake of 4 to 8 glasses of water.(1)

Valtin emphasizes that his conclusion is limited to healthy adults. But barring that exception, he concludes that we are currently drinking enough and possibly even more than enough.

Despite the dearth of compelling evidence, then, What's the harm? "The fact is that, potentially, there is harm even in water," explains Valtin. Even modest increases in fluid intake can result in "water intoxication" if one's kidneys are unable to excrete enough water (urine). Such instances are not unheard of, and they have led to mental confusion and even death in athletes.

And he lists other disadvantages of a high water intake: 1. possible exposure to pollutants, especially if sustained over many years;2. frequent urination, which can be both inconvenient and embarrassing; 3 expense, for those who satisfy the 8 x 8 requirements with bottled water; and 4 feelings of guilt for not achieving 8 x 8.

Other hazards associated with enhanced water consumption. Hyponatremia is a situation where too much water consumption has resulted in the dilution of sodium and other essential chemicals in the cells of the human body. In the extreme, this can lead to death. Another concern is that more drinking of water leads to an enhanced consumption of pollutants in water - both bottled water and tap water contain bacterial and chemical pollutants that become absorbed in the body. Last but not least, bottled water is unnecessarily expensive. (1)

Another example of over-drinking: in 2002, several runners in the Boston marathon suffered from hyponatremia, and one of them died as a result. Several other marathon deaths have been reported - not as you might expect, from dehydration! Rather, they are a result of hyponatremia resulting from over-hydration. The elite runners (those who finish under 4 hours) are experienced enough to drink very little during the race, and do not suffer from this problem. However, the less experienced athletes (typically those who run 4 hours and more) think they need to drink profusely, and consequently suffer from this life-threatening problem. (2-3)

***Other claims discredited by scientific evidence that Valtin discusses include:

1. 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.

2. 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.

Is there scientific documentation that we do not need to drink "8 x 8"? There is highly suggestive evidence, says Valtin. First is the voluminous scientific literature on the efficacy of the osmoregulatory system that maintains water balance through the antidiuretic hormone and thirst. Second, published surveys document that the mean daily fluid intake of thousands of presumably healthy humans is less than the roughly two quarts prescribed by 8 x 8. Valtin argues that, in view of this evidence, 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.

Finally, strong evidence now indicates that not all of the prescribed fluid need be in the form of water. Careful peer-reviewed experiments have shown that caffeinated drinks should indeed count toward the daily fluid intake in the vast majority of persons. To a lesser extent, the same probably can be said for dilute alcoholic beverages, such as beer, if taken in moderation.

"Thus, I have found no scientific proof that every person must drink at least eight glasses of water a day'," says Valtin. While there is some evidence that the risk of certain diseases can be lowered by high water intake, the quantities needed for this beneficial effect is much less than 8 x 8, and the recommendation can be limited to those particularly susceptible to the diseases in question.

So everyone can quit feeling guilty that they're depriving themselves of optimum health, save your money and just drink when you're thirsty. Trust your body, it's smarter than you think.

Iron

References--

(1) "Drink at least eight glasses of water a day". Really? Is there scientific evidence for "8X8"? Am. J. Physiol. Regul. Integr. Comp. Physiol. v 283, p 993 (2002)

(2) "Drink plenty of fluids": a systematic review of evidence for this recommendation in acute respitory infections. British Medical Journal v 328, p 499 (2004).

(3) Hyponatremia among Runners in the Boston Marathon, New England Journal of Medicine v 352, p 1550 (2005)

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Myths about water