is a myth

Quote :

"12 August 2002 Recommended Water Intake A Myth 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 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. Valtin emphasizes that his conclusion is limited to healthy adults in a temperate climate leading a largely sedentary existence -- precisely, he points out, the population and conditions that the "at least" in 8 x 8 refers to. At the same time, he stresses that large intakes of fluid, equal to and greater than 8 x 8, are advisable for the treatment or prevention of some diseases, such as kidney stones, as well as under special circumstances, such as strenuous physical activity, long airplane flights or hot weather. But barring those exceptions, 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, 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) expense, 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 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. "

words

basically, most of the water they say you need, you get in food. The thirst = dehydration is incorrect. but it's not really a bad idea to drink 64 oz a day.

2/22/2007 12:33:18 PM

I could have told you it wasn't necessary b/c most people don't do it.

2/22/2007 12:36:15 PM

Quote :

"basically, most of the water they say you need, you get in food."

this is patently wrong.

are you saying that at least 50% of the water that the body needs, you get it in food?

[Edited on February 22, 2007 at 12:39 PM. Reason : ]

2/22/2007 12:38:23 PM

Quote :

"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."

yes, in prepared foods.

2/22/2007 1:09:07 PM

I was always skeptical that non pure water sources can't be utilized in the body in the same way that water is. That never made sense to me. If your body is breaking things down as it is, it seems like the water would come back out eventually and be usable in the same way.

2/22/2007 1:12:16 PM

^^ I somehow remember about that in AP bio back in HS.

It's close to 50% if not more. Your body breaks down carbohydrates to release water, and a lot of what you eat has carbohydrates in it. Not to mention just the water that is often added to foods in the cooking process.

2/22/2007 1:15:59 PM

Quote :

"healthy adults in a temperate climate leading a largely sedentary existence"

People who run or exercise = gallon a day.

2/22/2007 1:22:17 PM

well if heinz valtin says, then so be it.

2/22/2007 1:23:48 PM

I still drink water when I can to the point my piss is clear, then I'm good. I feel a lot better.

2/22/2007 1:24:37 PM

That's from 2002.... I wonder if anything else has come out about it.

2/22/2007 1:30:03 PM

doctors are forever trying to claim that former health guidelines are bogus, only to find themselves sounding like complete dumbasses when the next report comes out to the contrary 3 months later.

2/22/2007 1:46:58 PM

there is a report to support virtually any claim you can make.

2/22/2007 1:48:40 PM

some people will report claims that go completely against the research they did, just because they think no one will question it.

2/22/2007 1:51:06 PM

What's the recommended water intake to win a Wii?

2/22/2007 1:52:03 PM

i drink well over 64 oz a day, and i can definately tell a difference when i don't

2/22/2007 4:20:18 PM

I drink well over, but I also exert myself more than the average potato.

2/22/2007 5:11:50 PM

My Gallon Jug is my life blood.

2/22/2007 5:15:07 PM

^^ not saying it's a bad thing, me too, just not worth buying a shitton of bottled water...

i never feel any of this 'guilt' they talk about when i dont get 64 oz

2/22/2007 5:28:50 PM

Bottled water???

buy one bottle and use it over and over again. Buy a nalgene or shaker bottle and use it. Use a fucking glass....but buying bottled?


If you are drinking bottled, make sure you use a flouride rinse.

2/22/2007 5:31:07 PM

Regardless of this article, and regardless of whether you believe in the 8x8 rule, most people are silly in that they never talk about different requirements for different people.

First and foremost, your intake depends on your BW. A 150 pound male, and and 250 pound male, obviously don't have the same water need, even assuming same activity level, climate, etc.

As important, you have to look at climate and activity level. And water needs can vary wildly between different people because of those factors, even possibly by a factor of 2 or 3.

So, most people seem to be misguided on this issue.

Second, this doctor doesn't seem to give any recommendation on this topic. He is only refuting another recommendation. After reading the article, the question of how much to drink is still unanswered.

Also, the statement:

Quote :

""most of this quantity is contained in prepared foods,""

is also a blatant generalization, as blatant as the 8x8 rule. People have wildly different diets. If you are eating a lot of meat and pasta most of the time, you ain't getting much water from that. I know that water is a byproduct of the Kreb's cycle, i.e., it is produced whether there is water in the food or not, but that's a small quantity. As for absorbed water in food, as I said, differs a lot from food to food (for example, compare a meat + pasta diet with a vegetarian diet; there is a huge difference in water present in those diets). Furthermore, your water intake also depends on your diet; some foods require more water to be drunk with them for proper digestion, such meat. Also, if you have a high intake of fiber, you need to drink more water if you want to avoid blockages of your lower intestine.

And how can one explain away the myriads of anecdotes of people feeling better upon increasing their water intake?

It is better to be safe than sorry; I drink 3-4 litres a day, and I am not about to decrease it.

I have noticed in my case, that any less leads to constipation.

[Edited on February 22, 2007 at 5:54 PM. Reason : ]

2/22/2007 5:52:57 PM

pasta contains a ton of water, but your point is still valid. I can easily sweat out 32 ounces of water in my daily cardio, so I am not about to reduce my water intake based on this report.

2/22/2007 6:01:28 PM

Why would you reduce your intake based on this report? The entire thing is concerning sedentary people.

That isn't either one of you.

2/22/2007 7:22:05 PM

Hey, here's an idea:

If you're thirsty, drink some water. If you're not, don't.

Sometimes I go almost the whole day without drinking pure fluids, but I eat a lot of applesauce, fruit, yogurt, etc. All have water. If I'm not thirsty, I don't really see the point of forcing it. Then I have to pee much more frequently.

[Edited on February 22, 2007 at 9:00 PM. Reason : ]

2/22/2007 8:58:55 PM

still helps flush out the system a bit eh?

2/22/2007 10:31:19 PM

cotton mouth

2/22/2007 10:54:42 PM

drink when you are thirsty. it really is simple as that. not more, not less.

2/22/2007 11:35:36 PM

There's a difference between needing to drink that much and it just being beneficial to do so. Sure, people only need 1,200 calories per day, but if that's all anyone ever got, we probably wouldn't fare so well.

2/23/2007 9:48:16 AM

^ you'd be surprised on what you can get by on....

that said on swimming days i probably drink 64+ ounces of water, and 32 oz of gatorade at least... (more than 2 miles of swimming in 1.5 hours or less)

2/23/2007 10:09:46 AM

^ I think you missed my point. I said we can get by on little, but do we really just want to "get by"?

2/23/2007 10:15:06 AM

high hematocrit and blood viscosity are both hard on the kidneys and risk factors in heart disease, and reduced water intake causes both of them to rise. Just cause you can live on less water doesn't mean it's healthy, regardless of whether you're sedentary or active.

2/23/2007 10:29:11 AM

words

*sips on 2nd glass of water for the day*

2/23/2007 11:01:46 AM

Wouldn't say a myth, just a broad generalization.

A nutritionist can't know what a person is going to eat in a given day (not to mention special cases based on weight, age, medical conditions, etc), so they just give an upper estimate to account for someone that maybe eats a bunch of stuff lacking in water and things that dehydrate you such as alcohol and caffeine. On the other end you have people who eat a bunch of fresh fruits and vegetables and probably get most of their water from that, and don't need as much.

Either way, its only in rare cases that a few extra glasses of water will hurt you.

2/23/2007 2:13:28 PM

^^^Know what else is hard on the kidneys? Holding your piss because you drink so much water than you have to go every thirty minutes.

2/23/2007 9:14:00 PM

Why do you assume increased water intake means you're "holding it"? Can't you just go when you need to go? IPSO ERGO FACTO, AMIGO

2/23/2007 9:17:25 PM

It makes you less productive, for one. While urinating may be a pleasurable experience, the lead-up is not. I don't like the feeling of having to piss all the time, but that's just me. I can hold it, or I can go frequently. Doesn't matter, but neither is particularly desirable. I tend to trust my body's signals. You have thirst for a reason. If you're not thirsty, forget about it.

2/23/2007 9:26:47 PM

Is it a really bad thing to have more water than you need, I mean there isn't such thing as too much water unless you drink say 5 gpd or something ridiculous? Even if most people don't need 1 gpd is it gonna kill them to drink it? Having too much is certainly not as bad as not getting enough

Think of it this way, can you have "too much gas" in your car? Sure you could overfill the tank but not after the pump tries to stop you severl times first, just like your stomach. Your body will let you know when you have enough water, thirst and stomach pain are your biological fuel guages, listen to them, not some M.D. trying to get his 15 mins.

[Edited on February 26, 2007 at 3:10 PM. Reason : ]

2/26/2007 3:08:41 PM

yeah you can drink too much, but like you implied, it's quite difficult to do...

2/27/2007 9:54:46 AM