Alan-- I've never been able nor inclined to drink such a daily water quantity as is famously generalized, with the exception of occasional water-fasting. I developed a hypothesis about this, which I later heard a Dr. Parris more-or-less corroborate at a Preparedness Expo in Altanta: Dissolved substances transmigrate through permeable membranes, such as cell walls, according to their comparative concentrations on either side. Therefore, taking an overabundance of water contemporaneously with meals might not only hinder the digestion of foods by diluting enzymes in the alimentary tract, but also hinder cellular absorption by diluting bloodborne nutrients. (My philosophical studies of the Dialectic help to round out this perspective: Paraphrasing Ecclesiastes, 'there's a time to hydrate and a time to refrain from hydrating;' universal law consists of obligations & limitations based on temporal oscillation between polar opposites.) IOW, it's fallacious to prescribe a gross, quantitative quota about hydration or anything else without due consideration of *timing* and *proportionality*. Answering the question of 'how much water to drink' begins, therefore, as most intelligent replies: "It depends..."
--Russ ----- Original Message ----- From: "Alan Hulsebus" <[email protected]> Cc: <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]> Sent: Sunday, August 24, 2003 12:19 AM Subject: how much water to drink > > Theory doesn't hold water > > Scientific support for `8 x 8' rule lacking > > Bernard Trink > > Much of what we've had drummed into us since childhood is questionable if > not untrue, though we are reluctant to give up our beliefs (``Mummy and > daddy told me so''). Get ready to be shook up again. It comes from a news > release (truncated here) issued by Dartmouth Medical School (DMS). The need > to drink eight glasses of water a day is questioned. > > Hanover, New Hampshire _ 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). > > 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 recommended approximately ``1 millilitre 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. > > 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, in teenagers after ingesting the recreational drug Ecstasy, and in > ordinary patients. > > And he lists other disadvantages of a high water intake: (a) possible > exposure to pollutants, especially if sustained over many years; (b) > frequent urination, which can be both inconvenient and embarrassing; (c) > expenses, for those who satisfy the 8 x 8 requirements with bottled water; > and (d) feelings of guilt for not achieving 8 x 8. > > 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 colour, 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 > regulatory 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.'' > > B.T.: Controversial certainly, but the professor emeritus of physiology at > Dartmouth Medical School is no quack and hardly irresponsible. What he says > may not change your mind, but it might make you wonder. > > _________________________________________________________________ > Get MSN 8 and enjoy automatic e-mail virus protection. > http://join.msn.com/?page=features/virus > >
