Run Fat Boy, Run!

Starla put up another Daily Challenge.

Today’s Challenge: Get in at least the reccomonded amount of water today (8 tall glasses). I will be trying to finish my large water bottle 3 times.

That got me thinking.  Sam and I have been talking about the 8 glasses of water a day, or 8×8 myth recently.  We’ve concluded that although it might be a myth, it is likely still pretty good advice, and it shouldn’t hurt.

My physiotherapist recommended me to  drink 3-4 large bottles of water a day, until my urine is almost colourless and odourless.  Supposedly this should help my back.  Some days it seems it does, some days it doesn’t.  Some days I don’t drink water and my back is fine, others I do and it hurts.  The evidence thus far is anecdotal of course, but seems to not have a direct effect on my back.

So I went looking for answers, and found this interesting article, written by a  part of which I will crib:

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.

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 absolutely 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 may be less than 8 x 8, and the recommendation can be limited to those particularly susceptible to the diseases in question.

In case you doubt the authors credentials, I’ll crib quickly again, from the beginning of the article:

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.”

Hmm.  It would appear that the 8×8 rule really is a myth.  For more reading, you also might find interesting this article at snopes.com, which sums up thusly:

The best general advice (keeping in mind that there are always exceptions) is to rely upon your normal senses. If you feel thirsty, drink; if you don’t feel thirsty, don’t drink unless you want to. The exhortation that we all need to satisfy an arbitrarily rigid rule about how much water we must drink every day was aptly skewered in a letter by a Los Angeles Times reader:

Although not trained in medicine or nutrition, I intuitively knew that the advice to drink eight glasses of water per day was nonsense. The advice fully meets three important criteria for being an American health urban legend: excess, public virtue, and the search for a cheap “magic bullet.”