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Science

Is 8 Glasses of Water Per Day Overkill? 90

Posted by timothy from the drink-drink-drink dept.
An anonymous reader writes: "David Harris reports in his science news that the American Journal of Physiology today published a study dispelling the 8x8 myth. That is, the recommendation to drink 8 eight-ounce glasses of water per day has no scientific evidence behind it. The paper also mentions the risks of drinking too much water and explodes some other urban myths of water drinking such as the 'thirsty means dehydrated' and 'dark urine means dehydrated' myths."
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Is 8 Glasses of Water Per Day Overkill? More

Is 8 Glasses of Water Per Day Overkill?

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  • Have you ever tried drinking 8 glasses of water? You feel all bloated and can hardly move, and the first place you go is to the closest washroom to feed the sewers.
    • Have you ever tried drinking 8 glasses of water?

      I typicaly glug down quarts or half gallons of fluid at once, err, heh. a few 8oz glasses of water at once? Nothing to it. :) I may spread it out over the day but. . . . bleh

  • For once, the /. article summary says nearly as much as the linked-to articles themselves. It's funny, no matter how hard I try to challenge preconceived notions I have, there's always one more "well-known fact" I forget to look into.

  • caffeine/alcohol (Score:4, Interesting)

    by TRACK-YOUR-POSITION ( 553878 ) on Thursday August 08, 2002 @06:08PM (#4036051)
    The part about water in caffeine drinks counting towards you're recommended intake struck me as most contrary to my own anecdotal expereience--it seems like whenever I drink anything caffeinated, I'm thirsty for water shortly afterwards. I suppose this discrepancy is either in my head, a bizarre artifact of my own physiology, or a misinterpretation of the abstract linked to here.

    • Re:caffeine/alcohol (Score:4, Informative)

      by nelsonal ( 549144 ) on Thursday August 08, 2002 @06:19PM (#4036098) Journal
      Caffeine and Alchohol are both duretics, which means that in order to process them for removal water is required. While Alcohol in concentrated form is likely to dehydrate you, beer, coffee, and soda net water for you. I'm not sure about beer, I have seen reports, from dubious sources, that it takes 16 oz of water to process the alcohol in a 12 oz beer. Coffee might not be net water either depending on how caffinated it is.

    • Re:caffeine/alcohol (Score:3, Informative)

      by JabberWokky ( 19442 )
      Sugar makes you thirsty. I am not a big fan of sugar - I just don't like sweet, and it's very evident to me when I drink tea with no sugar versus tea with plenty of sugar that the latter does not kill thirst as well as the former. Note that I'm not a health nut anti-sugar freak; I love caramel and other forms of sugar, just not the sickly sweet soda kind. When I have sugar in my tea, I have loads of it, and also a ton of lime juice as well.

      It's also a "well known" fact among hikers and campers. But then, this article is about breaking myths.

      --
      Evan (no reference)

    • As I recall, things like coffee and ecstasy promote dehydration by making the uptake of water more inefficient. Also, I think your body has to filter out the nonwater parts of other drinks. I suspect that coffee is less efficient than water at hydrating you, but does not literally leave you with less water than you had before drinking it.
      • ecstasy promote dehydration by making the uptake of water more inefficient

        WRONG! (Emphasis added because this is important).

        Ecstasy just makes you feel thirsty, and tends to block the "okay, I've had enough water now" signal, so you keep feeling thirsty.

        Locally we had a 16 yr old girl go into a coma and die because of this. Took ecstasy, got thirsty, kept drinking water until she'd basically OD' on the stuff. The increased fluid volume caused cerebral swelling which induced the coma which she never recovered from.

        The friends that supplied the drug to her were charged, don't know what the current status of the case is.

        I suppose if you "know what you're doing" (although I question that assessment of anyone who voluntarily takes mind-altering drugs of unknown provenance) you can alleviate the thirst sensation with small sips without overhydrating. She didn't, nor did her friends.
    • It might very well be your own psychology playing you a trick, the same way my psyche makes me have to pee after I brush my teeth, even if I just did so right before brushing them. Please don't call the guys in the white suits!
  • It pisses me off that i can't read this without paying. I mean all were getting here is the watered down abstract. And the link will likely be hosed shortly anyway due to ./ effect.
  • I always thought it was cans of Coke!

    I might have to re-evaluate my daily drinking.
  • lets see, i drink about 3 cans of soda, 12 ounces each, since the first ingrediant is water id say about 8 to 10 ounces of the soda is water... so thats 3 of my eight, for dinner i drink water or something, probably another 2... so thats five, and probably about eight ounces for breakfast, damn thats 2 left. And even with 2 left i consider myself well hydrated... hmmm maybe eight is too much.
    • 12 ounces each, since the first ingrediant is water id say about 8 to 10 ounces of the soda is water

      There's pretty close to 12 ounces of water in a 12 ounce can of soda, but with caffeine you'll probably pee out 14 ounces.

    • I drink 1 glass of soy milk or a cup of coffee at breakfast. Then maybe two 12-oz beers in the evening and sometimes a 12-oz glass of juice at bedtime.

      That's it for maybe 9 days out of ten. not one drop of plain water, and at most 44 oz of other liquids (of which 32oz has diuretic properties). So either I'm getting the other needed 20 oz from the food I eat, or I guess I should have evaporated into nothing years ago.

      Maybe when I'm sixty I'll discover that my kidney's have given out but I doubt it. Humans evolved on the plains of Africa, not a place known for having a half gallon of potable water for evey individual available every day. It was also much hotter than the typical North American living in air conditioned buildings is typically exposed to. Given that I expect that I will be fine.

      Of course if I am going to be outside on a hot day I drink more fluids (even actual water on occasion) as I am going to sweat it out, but I don't sweat substantially in 70degF room typing at a keyboard.

      My guess is the 8 glasses a day recommendation, if it was based on any kind of science, came about prior to the wide availability of AC, and when most people worked in jobs that required using muscles others than those that move their fingers, wrists and eyes.

  • I think this paper is clear evidence that we all need to drink more Bawls. :)

  • NPR has the interview (Score:3, Informative)

    by wompser ( 165008 ) on Thursday August 08, 2002 @06:38PM (#4036215)
    Yup. NPR had a story with the author of this study this morning, quite interesting too...

    Guest host Renee Montagne talks with Dr. Heinz Valtin, doctor of physiology and professor emeritus at Dartmouth College, about a new study saying that people may NOT need to drink eight cups of water a day to stay healthy.

    story on npr.org [npr.org]

    Lets hope they got over the deep linking craop.

  • Not a Sop to Drink [snopes.com] (February 6, 2001)
    Water - the myth of 8 glasses [canoe.ca] (February 13, 2001)
    How much water do we really need? [cnn.com] (May 24, 2002)
  • The abstract [physiology.org] contained a sentence that caught my eye: " The search included not only electronic modes but also a cursory examination of the older literature that is not covered in electronic databases"

    Do the Physiologists have amazingly deep databases, or is something funny going on here?

  • Stupid (Score:2, Insightful)

    by TheOnlyCoolTim ( 264997 )
    Drinking water is good for you. Drink lots of water. When it is hot, humid, and I am outside, I can drink that 64 oz of water within an hour or less. The people who don't drink enough water get taken away in an ambulance.

    You are orders of magnitude more likely to experience dehydration than to experience the almost mythical "water intoxication." (Yes, it is possible to kill yourself by drinking too much water, but it happens very very rarely.)

    So ignore this article and go have a nice glass of water.

    Tim

    • Re:Stupid (Score:2, Insightful)

      by Reality Master 101 ( 179095 )

      Drinking water is good for you. Drink lots of water.

      Based on what evidence? I've always thought 8 glass of water thing was a crock.

      When it is hot, humid, and I am outside, I can drink that 64 oz of water within an hour or less. The people who don't drink enough water get taken away in an ambulance.

      Well, duh, obviously when it's hot and humid you need more water. But that's not what we're talking about. Under normal circumstances, you get more than enough fluids from the food you eat. Excess water/fluid just gets pissed out.

      • >Excess water/fluid just gets pissed out.

        Along with various toxins.

        Water helps to move toxins through your kidneys. Without "too much" water you wouldn't need to use the washroom, meaning you'd never urinate out those toxins, which common sense tells us is bad.
        • That's a danger in dry climates. Your body never feels sweaty because the perspiration evaporates so fast, and you can drink enough to not feel thirsty without ever filling your bladder. You have to get in the habit of drinking more than you think you need to keep the kidneys flushed out and the blood volume reasonable.

          (The latter is important at altitude, which tends to thicken the blood anyway.)
          • This is also a danger while driving in the summer with the windows down. You still sweat but the onrushing air wisks it away very quickly. I have driven hundreds of miles per day while drinking bottles of water ( >2) and still have not had to use the lav.
        • "Excuse me, but what do these toxins look like? Have you ever actually seen a toxin?" -- Stanley Marsh, 3rd grade, South Park Elementary
    • It's recommended [195.166.32.46] that people taking certain recreational pharmaceuticals put a limit on their water consumption, since some have an anti-diuretic effect.
    • Killing one's self by drinking too much water is exactly what happened to a girl here in the Denver area a few months ago. Coma, then death. (See my earlier post).

      But yes, dehydration (especially around these parts) is more likely.

      (BTW, if you happen to be female and pregnant, (or male and pregnant I suppose, but that's very very rare ;-), staying hydrated is especially important -- even slight dehydration can bring on contractions and early labor. Apparently the local maternity wards had a real busy day a few years ago during the Pope's visit because of the number of people standing out for a long time in the hot dry weather.)
    • Yah. I personally *never* drink any water, and it's never seemed to do me any harm. The only drinks I consume are beers, shots, soda... ah and about a pint of milk per day on cereal. Maybe it's the latter that has saved me.
  • You doctors have been telling us to drink eight glasses of gravy a day!

  • Partially switching from Diet Coke to Water (Score:3, Interesting)

    by daviddennis ( 10926 ) <david@amazing.com> on Thursday August 08, 2002 @08:07PM (#4036610) Homepage
    I used to drink about six cans of Diet Coke a day, plus one Diet Coke from the soda fountain at lunch.

    A friend I respected suggested that I consider drinking more water and less soda. He claimed that I would lose weight (I was 265 pounds at the time) and feel better.

    What I discovered is that I did lose weight, although not enough to significantly impact my appearance, but more to the point I felt better - I was generally more alert in the afternoons, and after a while just a few sips of a Diet Coke would give me more energy (when I needed it) than a whole one would previously.

    It looks like caffinee becomes steadily less effective as more of it is used, so the simply exponent of abstaining from it and limiting its intake worked well.

    So I would recommend something like this to anyone trying to become more healthy. I started losing weight at a good clip, incidentally, when my new job responsibilities made me less sedentary. Annoying but good for me in the long term.

    D
    • You can certainly build up a tolerance to caffeine (and similarly, exhibit withdrawal symptoms from it).

      As far as losing weight goes -- I've heard that caffeine affects your metabolism such that it kicks blood sugar levels temporarily higher. This would do two things -- the higher blood sugar level prompts conversion of the sugar to fat, and when it drops again, it makes you hungry. That in turn would tempt you to eat more, and so on.

      I know I tend to eat less when I drink water rather than my usual several cans of diet pop (alternate Diet Coke and Fresca -- I don't need that much caffeine).
    • Often times dehydration is mistaken for hunger pangs. You may sit in your office for a good part of the morning without drinking a drop of water, then hunger may set in when it's actually your body telling you to take a drink of water. Those who misteken thirst for hunger will grab a snack rather than take a chug of water.

      I've personally noticed a lot of other benefits from drinking water over sodas, other than the weight factor like you've discovered. I've had an easier time concentrating on tasks, for example. Have you ever gone an extended period of time (like 6 hours or so) without a drink of water, then finally take a chug? I swear you can feel your cells getting immediately replenished like a dried up plant getting watered.

  • Granted, I have only read the abstract, but the research methodology strikes me as a bit weak. Whatever way you dress it up, it looks like this guy has just done a literature review.

    Now, if this was an article reporting on a study that followed the general health and well-being of a number of participants over a certain period of time, relating health to water consumption, with a control group given a placebo of, say, Mr. Pibb or something, then I would be a bit more inclined to read on beyond the abstract.

    If literature reviews get you a publication in the Journal of Physiology and a spot on NPR, then I think I'm in the wrong line of academic inquiry.

    Roll on tenure!

  • It was consume the equivalent of 8 glasses.

    You can get water from sources other than just a glass of water - for instance, all those servings of fruit you never eat.

  • First, I note the article uses as its evidence the lack of concrete scientific research to back it up. I've oft seen similar arguments in many a religious debate of any sort - and whether the presenting side is correct in that note is left as an exercise. But I digress.

    (Disclaimer: I am not a doctor)

    The whole 64 oz per day thing is a bit off, but here's why: water intake should actually be proportionate to body weight, but a surplus isn't necessarily a bad thing. Increase per caffeine intake (diuretic effect counteraction) and per physical activity increase (like Camelbak [camelbak.com] says, "hydrate or die").

    For instance, if a 150 lb random were to drink 64 oz of water over the course of 1 day and spend the day sitting in front of his computer, they would be well hydrated and urinating fairly frequently as a side effect. (They would be lethargic due to caffeine withdrawal, but they would be very well hydrated.) If the same 150 lb random ran a marathon and only consumed said .5 gallons of water over the course of the run, they'd be cramping from heat exhaustion by mile 24. (Seen it.)

    Now take a 300 lb random. If they spent the day in front of the computer and gave them 1/2 gallon of water to drink over the day, they'd be particularly thirsty to the point where they would feel dry. Increase the water intake and they'll feel better. And if your random is running a marathon, that 300 lbs better be muscle lest he wear himself out despite proper hydration.

    (end disclaimer section)

    More data can be found by doing a google search [google.com], natch.

    • I agree with your assessment that 64 oz. of water is not optimal for different body weights and activity levels. Instead, I use this formula:

      (body weight in ounces) / 2

      The formula gives you a more optimal amount of water for your weight. For example, a 150-pound man would drink 75 ounces of water per day. Adjust the number based on your activity level.

      Also, you should drink the water gradually throughout the day. Drinkin a bunch of water all at once won't help you that much. Your kidneys will just remove the excess water from your system to maintain osmolarity and plasma levels.
    • This guy shows a substantial amount of evidence that most of the supposed benefits of drinking "lots" of water are either unsupported by research or shown to be achieved with substantially less water intake than the 64oz recommendation. He also has some anecdotal evidence that caffinated beverages and to some extent beer not being particluarly dehydrating.

      But the most important thing to note (I think) is that under normal circumstances the body's thirst mechanism is entirely sufficient to prevent dehydration.
  • Use it on the field!! h2O...gaatoraade...h2oooh...water sucks, it really really sucks ------ now that's some high quality h2O ------ courtesy of the waterboy..come get me MPAA!!!

  • Medical Geek Speaks Out (Score:5, Informative)

    by kalamazoo904 ( 312444 ) <[allen_bryan] [a ... hms.harvard.edu]> on Friday August 09, 2002 @01:31AM (#4037662)
    1) It is true that 8 glasses of water need not be drunk each day. It *is* true that the equivalent, two liters of fluid, must be consumed -- but food contains 30-50% of the water you need each day.

    2) It is true that "being thirsty means you're already dehydrated" is an exaggeration, but it is an intentional one. It means "you're well on the way to being dehyrated". The exaggeration is, I suppose, intended to catch ID10Ts who ignore thirst even during 10-km runs in 110 degree weather. Thirst does kick in well after you have lost plenty of fluid, and once ADH (anti-diuretic hormone, the hormone that controls urine production and volume status) has already risen. These facts, I suppose, are the origin of the common anecdote.

    3) "Dark urine doesn't mean you are dehydrated" -- not true. It *is* true that it is difficult to judge from color alone. Despite our 16 million color resolution, it is hard for people to subjectively grade color without experience (i.e. working in a urinalysis lab); thus, judging hydration by urine color alone will have a high error rate and often be inconclusive. Other factors, such as urine contaminants, might make the test less accurate. Along with other clues, however (i.e., being sweaty, thirsty, and tired), it may be useful.

    4) "Water intoxication", a peculiar form of hyponatremia (low blood sodium concentration), is *not* mythical. However, it *is* much rarer than dehydration. It takes a special kind of person (read: mentally ill patient) to drink the 25+ glasses of water per day that it requires to achieve this.

    5) Studies have shown (sorry, I don't have links, its 0130 around here) that caffinated beverages such as Coke hydrate at about 2/3 the rate of pure water. That is, at Coke concentrations, the caffeine dose is sufficient to cause you to lose 1/3 of the water you just drank as part of the Coke.

    6) These indicators -- thirst and dark urine -- are not "myths" and not useless (although they are far from perfect). I happen to know first-hand that some of the best doctors in the United States use these observations in their daily assessments of patients.

    7) "Absence of evidence is not equal to evidence of absence." --paraphrased from Carl Sagan

    This fellow has done very little experimentation on his own, but simply collected the lack of research combined with evidence from his own student experiments over the years. While this is a provocative article, it is intended to stimulate research, and NOT to be the definitive work on the subject. What's needed (as he states at the end, in A CALL FOR DIALOGUE) is more and better (and better funded, pretty please)nutritional research!

    Disclaimer: IANAD (but I am in medical school and work with 'em in hospitals every day; see address.) And yes, I am a geek. Been programmin' since age four (BASIC on a c64), researchin' at MIT. Good enough for youz?

    • 1) How about some references for this, other than just your word?

      2) Depending on how one quibbles over the meaning of dehydrated and thirsty, various correlations can be supported.

      3) In other words, there are so many variables and exceptions, that dark urine doesn't mean you are dehydrated.

      4) In other news, eating 25 pounds of food at one sitting can be hazardous to your health.

      5) Further revelations show that alcohol is also a diuretic.

      6) Certain myths are not myths as long as you account for the 1001 exceptions and variations that make them hard to pin down.

      7) Just because you didn't cite any references other than your self-proclaimed "medical-geekness" doesn't mean there are no references, therefore we should trust you.

      And just how much experimentation on your own have YOU done as a medical student?

      Nope, not good enough for me. Go exhibit your ego elsewhere.
    • I just wanted to express my exasperation at the two negative replies to your post - don't listen to them! If only I had mod points...
    • 4) "Water intoxication", a peculiar form of hyponatremia (low blood sodium concentration), is *not* mythical. However, it *is* much rarer than dehydration. It takes a special kind of person (read: mentally ill patient) to drink the 25+ glasses of water per day that it requires to achieve this.

      i think i was once intoxicated by water. with 2 friends, i drank 4 liters in 20 minutes. it was a contest to see if we could do it and who could do it fastest. the contest was spurred by the fact that our H.S. chem lab had 4 litre 'battery jars' that we cleaned out and filled with water. my friends finished in 15 minutes but puked it all back up within 10 minutes. i kept it down but and pissed it out during many rushed trips to the bathroom over the next 2 hours.

      anyway, i think i was feeling a bit 'drunk' but it could have been the insanity which was apparently controlling me at the time....

      p.s. drinking that much tap water is very hard to do -- after the first litre all you can taste is chlorine and you gag before each sip! so it's really not any fun.
    • There are few better ways to get angrily flamed than pointing out the fact that you attend (or used to attend) MIT. A lot of people here wish they'd gotten in. Please disregard the imbicilic posts above.
    • "Absence of evidence is not equal to evidence of absence."

      I want this for my new sig! What's the source of the quote? Thanks.

  • I live in Santa Fe, New Mexico. It's a high desert region; the altitude is seven thousand feet and we get about a dozen inches of rain this year.

    If you don't want to get seriously sick here, you must drink mass quantities of water. My first visit to New Mexico was a hiking trip I took when I was fourteen. The rangers recommended eight liters of water a day, which probably was overkill--but not by so much as one of my companions thought, who ended up spending a night with some pretty bad nausea from the altitude and lack of humidity.

    It's true that you might not need quite so much in less extreme climates, but it's a great deal harder to give yourself water intoxication than to get dehydrated. Besides, it gives you an excuse to get away from that accursed keyboard.
  • everyones body is different. you should only need to drink as much as it takes for you to start peeing white.

    forget the 8 glasses a day thing. listen to your own body talk.

  • After this story, and one yesterday aboutt he size of drinks cups also in ounces, I've looked up the conversion rates to see what you're all talking about

    from this web site [eserver.org] :

    1 American fluid ounce = 29.57 millilitres.
    1 British fluid ounce = 28.41 millilitres

    So the American 8oz cup is just under a quarter litre (or around halfway between a 1/3 and a 1/2 English pint, if that's more your kind of reference size....)

  • drinking too much water ... explodes

    So that's what happens! Guess I'm not thirsty now. :O

    -Ed

    docbrown.net [docbrown.net]
    Graphic Design, Web Design, Role-Playing Games...all the good stuff
  • WCVB [thebostonchannel.com] yesterday reported an instance of a Boston Marathon runner dying of Hyponatremia [thebostonchannel.com] -- overdrinking water.

    8x8 may still be a good idea, but relieving yourself from all that water is just as important.

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