Best practices for water imbibing: "Just drink when you're thirsty"

NPR talked to scientists who say that the benefits of drinking tons of water are overrated, and that you don't need to carry a water bottle for a stroll around the park -- "Just drink when you're thirsty."
Myth No. 1: Drink Eight Glasses Each Day
Scientists say there's no clear health benefit to chugging or even sipping water all day. So where does the standard advice of drinking eight glasses each day come from? "Nobody really knows," says Dr. Stanley Goldfarb, a kidney expert at the University of Pennsylvania.

Myth No. 2: Drinking Lots of Water Helps Clear Out Toxins
The kidneys filter toxins from our bloodstreams. Then the toxins clear through the urine. The question is, does drinking extra water each day improve the function of the kidneys?
"No," says Goldfarb. "In fact, drinking large amounts of water surprisingly tends to reduce the kidney's ability to function as a filter. It's a subtle decline, but definite."

Link (via Kottke)


  1. Let me eat when I’m hungry.
    Let me drink when I’m dry.
    Lend me dollars when I’m hard up.
    Religion when I die.

  2. I’m _always_ thirsty. This comes from being a trainer in the past, I think. I’d spend the whole day talking, and that makes you thirsty, so I’d drink huge amounts of water. Now, even though I don’t train any more, I still feel the need to drink constantly.

  3. I’ve said this is bs for years and ppl just look at me like ‘yeah, like you know anything.’

  4. #3 t3knomanser: Or it might come from having diabetes. Maybe your body is telling you something.

  5. First, kudos for the Moonshiner quote above.

    Second: Myth #4 could use tweaking, or at least expanding. I’ve heard before that sometimes people misinterpret thirst as hunger. I know I do this occasionally, and drinking a glass of water before I eat usually helps me keep my portion size reasonable.

    Either way, a can of diet soda, with all the sodium and unpronounceable chemicals, CAN’T be equated with water for any kind of benefit. That’s just foolhardy.

  6. They only started to say that after water started to be bottled…and sold..


    Who do you think began the myth?

  7. What’s this?
    They’re saying we have a built in sensory apparatus for telling us when we should drink water?

    In other words:
    They’re saying evolution has given us enough sense to keep our bodies alive and at peak condition?


  8. #7 “Either way, a can of diet soda, with all the sodium and unpronounceable chemicals, CAN’T be equated with water for any kind of benefit. That’s just foolhardy.”

    [sarcasm]It’s got what plants crave.[/sarcasm]

    Seriously, if you suffer from sodium deficiency you have very serious problems indeed.

  9. I studied physiology at uni, and we learnt that the body is already at least partially dehydrated when it sends the “I’m thirsty” signal

    I was surprised they didn’t mention that, although perhaps they were on a slightly different tangent

  10. By the time you’re thirsty you’re already 2% dehydrated, according to the US Army Survival Manual.

  11. This is allegedly due to a slip up in a report by the National Academy of Sciences:
    “Paul Thomas of the National Academy of Sciences in Washington had
    the best explanation.

    The academy’s Food and Nutrition Board publishes the U.S.recommended daily allowances. The first edition in 1943 didn’t mention water. The next edition, in 1945, did.

    ‘A suitable allowance of water for adults is 2.5 liters (83 ounces) daily in most instances,” the book states. “An ordinary standard for diverse people is 1 milliliter for each calorie of food. Most of this quantity is contained in prepared foods.’

    Somehow, the final sentence was lost in the translation.Most doctors and nutritionists say people don’t need to drink every one of those eight glasses of water if they eat the proper

    “Skip those 8 glasses of water? Idea is all wet”
    Chicago Tribune – Chicago, Ill.
    Author: Bob Condor
    Date: Feb 29, 2004


    Oh, and don’t forget to start a 50 billion dollar industry based on nothing but the usual nutrition hucksterism and marketing and thereby creating an incredible amount of packaging waste.

    Some appalling statistics for you slurpers out there:

    Interesting bottled water statistics:

    * Americans drink more bottled water than coffee, milk, or beer. (Don’t go rushing to sell your Starbucks or Anheuser-Busch shares quite yet though)
    * In 1976, the average American drank 1.6 gallons of bottled water per year. Just last year in 2007, the average American drank over 28 gallons of bottled water. In over thirty years, we have increased our bottled water consumption by over seventeen times.
    * Fiji Water produces 1-million bottles/day while 50% of the residents in Fiji don’t even have reusable drinking water.
    * The only drink that outsells bottled water is carbonated soft drinks which totals to an annual consumption of 52.9 billion gallons.
    * Bottled water is a 50-billion dollar industry worldwide with bottling companies like Arrowhead, Poland Springs, Crystal Geyser, and Saratoga Springs.
    * 24% of US bottled water is tap water purified and repackaged by Coke & Pepsi (aka purified municipal water).
    * Pepsi’s Aquafina is the #1 selling bottled water with 13% market share while Coke’s Dasani bottled water is #2 with 11% market share.



    and the industry is lawyering up in Washington, retaining Van Ness Feldman to lobby against taxes such as the 5¢ per bottle tax that Chicago has put on the products, largely as a result of the huge amount of waste it generates.

  12. I heard that NPR report and one caveat they mentioned was for those who suffer from kidney stones. Drinking a good amount of water is important to those who suffer from this malady.

  13. Why is 2% dehydration a bad thing? It is not an argument to say, “When we are thirsty we are already partially dehydrated.” It’s just a statement.

    It could be interpreted in lots of ways, like: when we have 98% of our nominally optimal water level, our body sends a signal that we need to top up. Sounds pretty efficient to me, and the notion that a natural regulatory process within our body needs conscious tweaking sounds kinda suspect. Maybe our systems go off-kilter if we try to subvert the natural regulatory process by prematurely topping up. That’s just speculation, but it seems no less plausible to me than the speculation that letting ourselves get down to the 98% level before topping up is somehow bad for us.

    It’s only if you believe for some reason that 2% dehydration (whatever that actually means–how does one measure dehydration?) is a bad thing that you would take “we are already partially dehydrated” as reason to drink before we are thirsty.

    So what is the evidence? Do people who only drink when they are thirsty die earlier? Do they suffer from more illness? Are there any actual outcome measures by which they are worse off?

  14. I had heard that if you’re thirsty; you’re already dehydrated.

    My wife always has a drink in hand, of water. She drinks and drinks and drinks. I may have to urge her to see if she may be diabetic.

  15. As someone who has suffered (and I mean suffered) from a kidney stone in the past, I now drink a lot of water. My urologist recommended outputting at least 2 liters a day, which required drinking considerably more than that. The point is not to remain hydrated but to keep the urine as diluted as possible. The more concentrated the urine becomes (as you dehydrate), the more opportunity for minerals in your urine to crystalize and begin forming stones.

  16. But Tom, clearly we must all be operating at 100% maximum efficiency at all times. Any slight decrease in operating capabilities is analogous to a moral failure … you’re not doing everything within your power to be the most productive little cog in the economy you can be.

  17. To be fair, there are pretty serious risks associated with getting dehydrated, so it’s definitely preferable to overestimate the amount of water you need any time you might be in danger of dehydration.

    When you’re physically active, or overheated, or simply distracted for long periods, it’s very possible to become dehydrated to the point of danger without realizing how badly you need water. You don’t have to lose a large percentage of the water in your body before you start going into shock from insufficient blood volume.

    So, it could be that the 8 glasses advice was stressed to people doing lots of exercise, or working in the sun all day or whatever, since they were at real risk for dangerous dehydration if they didn’t consciously monitor their water intake. Then maybe it was generalized by non-experts as advice for everyone later. Like I said, considering the serious and immediate harm involved in dehydration, I far prefer to overestimate my water needs than just assume that when I need to drink I’ll notice that I’m thirsty.

  18. “drink when you’re thirsty” is not that simple:

    Your brain doesn’t always pay attention to your body. For example, “eat when you’re hungry” is why some people are overweight: they feel hungry even when they really aren’t, so they eat more than they need. A lot of things can cause that: stress, boredom, depression, sleep deprivation, malnutrition, etc..

    The opposite tends to happen with thirst: I personally find that I don’t always feel thirsty even though I should be. I’ve often gone from a hour the gym straight through to other activities, never once feeling like I was thirsty.

    The dehydration nausea and headache hits me about a hour after my workout, which is when I SHOULD have been rehydrating. I’ll go all day at work without sufficient hydration and end up not feeling so good by the time I get home. Caffeine is bad for suppressing thirst as well as appetite.

    I find keeping bottles of water visible will remind my brain to pay attention to thirst signals from my body.

  19. # 11, I too have studied Anatomy & Physiology at university. My Professor one Dr Paul Finn is a leading expert on heat acclimatisation and has done extensive work for both the Australian Institute of Sport and the Australian Defense Force on the subject of hydration and effects on performance.

    In his series of lectures on the kidneys he was very clear that the thirst response lags significantly behind the hydration state of the body. This is no problem when a person is in a cool climate and water loss is slow, but in a hot and humid climate, or under heavy exercise the body is losing water at a much faster rate.

    The difference between the daily water needed by a person at rest in a cool climate to one exercising hard in a hot and humid environment is something on the order of 20X.

    Under hot and humid conditions, the body’s thirst response is significantly lacking. If a person only drinks when they are thirsty then they will be perpetually dehydrated.

    That said, there are other ways to notice that you need to drink more. A dry mouth, a salty taste in the mouth are two such indicators, and both may precede thirst.

    The most effective method of monitoring your own hydration level is to check the colour of your urine when you pee by looking into the bowl. If it is clear, then you are drinking sufficient water. The more yellow and concentrated the urine, the more dehydrated you are.

    These simple facts are vital to healthy living in the harsh Australian environment. People die every year because they don’t know them.

    EyeSpy Guy

  20. I read in a book — and, I think it was “The 80/10/10 diet” — that people aren’t meant to drink too much, evolutionarily speaking. It has to do with the positioning of our eyes, which face forward. This would have been disadvantageous for us as a species as we “went down to the lake or river” (so to speak) to drink. (Other animals have their eyes set wider apart and are therefore better equipped with wider fields of vision to see predators approaching.) The book also suggests that most of the water we would need would be present in the raw (uncooked) fruits and vegetables we eat. So, if you cook your food (which most people do), you probably need to drink more water than if you eat a diet higher in raw veggies & fruits.

  21. Well, I was going to say that in my case, the admonition to drink lots of water came from my urologist after one of my kidney stones. I see that angle has already been covered. (I haven’t had a stone in almost two decades now, possibly due to taking magnesium daily.)

  22. I would certainly agree that forcing water doesn’t help at all.

    However, keep in mind that in hot climates and under physical exertion, you may dehydrate faster than you realize. A little preemptive water can be very helpful under such circumstances. Once your body dehydrates to a certain point, you will suddenly feel very tired and very stupid, and recovering may take several hours.

    I live in Phoenix, Arizona, where temperatures routinely top 100 degrees F. for at least half the year. Around here, carrying a water bottle is a very useful practice.

  23. #21: Solid, intuitive logic. I concur wholeheartedly. Though I haven’t quite gotten the keeping a Nalgene in clear sight thing down without chugging all day long.

    Per Myth 3: Skin elasticity is a primary indicator of dehydration for Wilderness First Responders… so maybe not healthier LOOKING skin, but it definitely affects the health of the skin. Skin cells lose their vibrancy as they lose moisture.

    Per Myth 5: It is relative to the individual. I have an accelerated metabolism and even though I am in excellent shape, I sweat furiously at the first sign of exertion. I will potentially dehydrate every time I work out.

    I admit I drink WAY too much water. I personally like to throw in some color the form of a pure juice or electrolyte mixture in order to make sure my body is actually even processing the liquids I force into it. Occasionally they will go right through me and I obviously need to chill out on the intake.

    If you’re using electrolyte and potassium supplements can’t your body use more water to greater efficiency? I tend to look at water as a lubricant, helping blood flow and muscle elasticity, and just hope I’m not overworking the kidneys, liver and bladder in the meantime…

  24. I heard this story and was furious. This guy is an idiot. I’m not saying he doesn’t know his area of science, but when you only tell part of a story in confuses things. Yes, you don’t need to drink 8 glasses of water a day, but you DO need to drink some or you WILL be dehydrated which plenty of people are. Not just people that are physically active, but plenty of us folks that are trapped at desks and forget to stop typing or put down the phone and get some fluids.

    I was a little stunned NPR just let this guy’s comments fly without any kind of counterpoint or clarification. And after the crazy cold and flu season we had this year…damn.

  25. Dihydrogen monoxide rules!

    I have heard of athletes overhydrating to the point of death, so its not merely a harmless myth.

    Dehydration is also the easiest way to lose weight!


  26. @#23BSUWG
    The 80/10/10 diet was written by Dr. Douglas Graham. First of all he is a chiropractor not a nutritionist. There is no scientific basis for there being an optimal diet from an evolutionary stand-point. Humans, as a species have spread into practically every part of the globe, modifying their bodies according to the conditions and foodstuff found wherever the went. Its a bit like saying we should all go and find somewhere to live that replicates the conditions on the savannahs of Africa where our species first arose.
    Dr. Graham is called one of the fathers of the modern raw food movement whose main ideas about enzymes are based on discredited scientific theories from the first half of the 20th century. All the evidence shows that humans have always been omnivorous. This is coming from a lifetime vegetarian. The fact I can choose this diet has everything to do with where and when I was born. If I was a hunter-gatherer, such a choice would be terrible from the point of view of survival.
    So I wouldn’t put too much stock in the idea that the position of your eyes dictates how much water you should drink.

  27. Drink when I’m thirsty? What if, whenever I get thirsty, I get a headache and can drink three liters of water before I have to use the bathroom?

    Thanks for the medical advice, Boing Boing!

  28. Um, but why not drink 8 glasses of water? Jeez, it’s not like water tastes bad. I personally feel better throughout the day when I’ve drank enough water, granted thats rather empirical.

  29. The LA Times did a very good article on this subject a few years ago. They surveyed a range of health professionals and found NO support for the 64 ounces rule. Personally, I almost never drink water. Maybe once a week. Lots of coffee in teh cold weather and lemonade when it’s hot.
    One urologist in the LAT article said that if you need to urinate at least 3 times a day you’re probably taking in enough fluids. That sounds like a very practical way to measure it.

  30. Drink when you’re thirsty. Psh! What will they think up next?! Eat when you’re hungry?

    I love how common sense is now “science”.

  31. While I agree that you should drink when thirsty, I also think that it’s important to carry a Nalgene-esque bottle of water around. Why? Because that way you don’t spend $3 for a plastic bottle of water bottled and shipped from far away when you are thirsty. Nothing makes me crankier than having to pour out my water bottle before entering TSA hell only to be told to buy $5 bottles inside and have the tap water on hot-only.

  32. one caveat they mentioned was for those who suffer from kidney stones.

    Which, by the way, is a hell of a lot of people. Do you know how you find out that you have kidney stones? Let’s just say that it’s pleasanter to drink eight glasses of water every day than to have a jagged, little rock try to push its way through your ureter.

  33. The doctor told me I should only drink 45 minutes before bedtime.

    (Offstage:) Well, did you take his advice?

    I tried, but after half an hour I had to stop.

  34. There are advantages to drinking lots of water that haven’t been mentioned here.

    For example, it’s one of the two most important ways to prevent constipation (the other is eating fiber). It also helps you digest the food you eat.

    It can also prevent headaches, especially sinus headaches. (I’ve suffered from these my whole life).

    How do I know these things? Personal experience. Plus, I came up with a revolutionary new research approach: I asked my doctor.

    As for people who buy bottled water: unless you live someplace where the water is going to make you sick, I’m sorry, but you’re a sucker!

  35. In the LAT article, a nutritionist said that drinking too much water could interfere with absorption of some nutrients in food.

    And why are we all so frightened that we’ll suddenly get dehydrated if we haven’t consumed precisely the required amount of fluids at the right time? The body regulates its fluids pretty accurately within broad ranges of intake and need.

  36. I don’t think the point is to stop drinking water. But it is reasonable to question the “everyone must drink 64 ounces of water every day” rule. How was it determined? Basically it was just made up without supporting evidence.

  37. “Just drink when you’re thirsty.”

    if you have ever been at a rave telling dancers to drink when they are thirsty is like the Pope telling african poor people that instead of using condoms they should just give up having sex to be safe from AIDS…

    if you are a street worker (Especially duing summer) 8 glasses a day when you don’t eat fresh fruits and vegetables (and food rich of water) are barely enough to keep you healthy.
    If you eat a lot of yogurt, fruits, fresh vegetables problably you can drink a couple of glasses of water…

    Water is good! Tap water is GREAT!

  38. #38 and #39: absolutely.

    People take things to extremes, and it’s human nature to uncritically latch onto any figure that supports a belief you hold (eight glasses, for example).

    People who, to quote Lewis Black, go around proclaiming “My pee has no color! My PEE has no COLOR!” are overdoing it. Moderation is the key, people.

    As per dehydration: there are different levels. Anyone who has seen a real case of dehydration knows that Josh and Britney powerwalking through their yuppie neighborhood have never been there.

    Having slightly less water than you need can result in some discomfort, though. Drinking enough water is just part of good nutrition.

  39. I drink between one and two 64oz Double Big Gulps of water (it’s a great container) per day. I’m not thirsty… I find that if it’s right there I drink up, but if it’s empty I’ll be fine.

    I started on the water when I cut out 8-14 Diet Pepsi’s a day, cold turkey. That stuff is addictive, and probably wasn’t too healthy for me.

  40. I wonder if thirst is a reliable indicator. If people with eating disorders lose the ability to use hunger as an accurate indicator, can thirst become inaccurate as well?

  41. I love people who complain about people who drink bottled water.

    Not everyone lives in a city with nicely purified water that has a totally neutral taste. A very large number of people drink water from wells, and they do not have sophisticated filtration equipment. My last home, the water was fine for washing, and even to some degree for cooking, but it had an awful taste when it was cold, from some trace minerals or something. We tried a brita filter, but it didn’t help much… so we bought gallons of water for drinking, at something like 30 cents a gallon.

    Now, I love my tap water at home, but the stuff at works tastes like it came out of a garden hose, so now and then I buy a bottle of water from the gas station. But most of the time I just drink tea or diet soda. Or bring a litre of water from home.

    But if I’m out, and I buy a bottle of water for a buck… so what? I’m paying a premium for cold and convenient. Would these people who complain about bottled water complain identically if I’d bought, say, a bottle of iced tea or lemonade?

  42. Narual: consider, please, the possibility that people in your situation are not the people we are “complaining” about.

    People with crappy tap water are not my target. People with perfectly fine tap water who waste their money and fill the landfills with non-biodegradable plastic water bottles are.

  43. It can and does happen that “just drink when you’re thirsty” equals “drink lots and lots” without diabetes.

    I’m just finishing up glass number nine, and it is seven PM. I’ll drink another two to three glasses at least before bedtime. Not because I have a goal in mind, but because I want that much. My average water consumption the last time I tracked it was 12 glasses a day. I’ve drank that much daily for years. (Heck, for a little while some medication I was on made me drink closer to sixteen.)

    I’ve been tested for diabetes, most recently last year, and I’m not diabetic.

    And hey, Thinkerer @#13 – Just because I’m a “slurper” that doesn’t mean I drink bottled water. You’re conflating two unrelated things.

  44. “Maintaining adequate fluid balance is an essential component of health at every stage of life. Age-related changes make older adults more vulnerable to shifts in water balance that can result in overhydration or, more frequently, dehydration.”

    “Maintaining good hydration status has been shown to positively affect urolithiasis (kidney stones) and may be beneficial in treating urinary tract infection, constipation, hypertension, venous thromboembolism, fatal coronary heart disease, stroke, dental disease, hyperosmolar hyperglycemic diabetic ketoacidosis , gallstone disease, mitral valve prolapse, and glaucoma. Local mild hypohydration or dehydration may play a critical role in the pathogenesis of several broncho-pulmonary disorders like exercise asthma or cystic fibrosis. In bladder and colon cancers, the evidence on hydration status’ effects is inconsistent.”

  45. I have taught about this topic for 20 years now postdoc to physicians in a board-certifying sequence in nutrition. I still find the issue confusing, as do my students, as I present conflicting opinions and studies to them.

    One part that seems consistent is that, unless one has special needs, e.g. sweating a lot in athletics, e.g. susceptible to kidney stones, the average person does not seem to overtly suffer from what some would deem as dehydration. For example, the average person does not overtly suffer from waiting until they are thirsty, despite the lag between physiological dehydration and the mind getting past survival programming (the body often doesn’t warn us of minor things, I assume so we can “get on with it” in a possibly scary world) and otherwise the mind allowing for the thirst to be noticed and acted on.

    The piece encouraging large-ish imbibing of water/fluids that I haven’t seen any research denying is bioimpedance analysis (BIA). None of the physicians, scientists, etc that I’ve read thus far (please educate me if you know different), saying “no, you don’t need that much water”, take on the BIA research/findings. Some of them I’ve been able to confront directly and everyone said they didn’t know enough about BIA to discuss it.

    Make BIA equal the electrical readings of the body’s tissues (e.g. electrodes put at hand and at foot on one side of the body) that get plugged into (computer software) equations to give phase angle (correlated to membrane health, and supposedly vitality, though I find that a vague concept), lean vs fat body mass percents, hydration overall, and extracellular vs intracellular water percents (e.g. as one indicator of inflammation, e.g. as part of some hormone balance analyses).

    I patiently watched BIA be used, watched the research and more in-the-field clinical literature accumulate, saw the hundreds of clients we treated in an AIDS clinic be analyzed with it with subsequent good interventions, etc, over years. I finally had to admit that it was a more valuable tool than just getting people to lose their excess fat mass — it seemed quite valuable for above mentioned membranes, inflammation, and hydration.

    At that point, I surveyed clinicians who had been using it for years and asked them what amount of fluids, especially water (since sometimes highly-sugared and/or highly-caffeinated fluids seemed to make them BIA “dehydrated”), seemed necessary to hydrate folks, to make their BIA say “hydrated”. The answer consistently was approximately “divide your body weight in pounds by 2 and that is how many ounces of fluid to drink a day as a good first guess”.

    I don’t want to believe it. E.g. so many clients find it too difficult to achieve that amount of fluid intake, even taking into account fluids in their food. However, again and again, I see the BIA show dehydration unless they are close to that amount of fluid intake.

    And when one is dehydrated, the rest of the BIA is not as accurate — the dehydration throws off the, e.g., fat vs lean reading.

    So, either the many years of research and clinical work came up with wrong equations for the BIAs “cells and fluids” readings/analyses, i.e. BIA is saying people are dehydrated when they really aren’t, or indeed many people have to do more than 64 ounces of fluid a day.

    Perhaps too much beyond the level of these comments but I’ll say it anyway: 24-hour urinary and spot salivary checks of adrenal cortex function in most clients I see suggest that hydration issues are secondary to adrenal function issues — people wouldn’t have so much trouble staying hydrated if adrenal function were better. Barnes Foundation and Brownstein knowledgeable physicians would claim that many people are also functionally low thyroid, which also contributes to dryness of skins. Omega-3 fats touters would also say many people are deficient in EPA+DHA and that also contributes to dryness of skins. So skin dryness (and maybe, thus, also poor handling of hydration by membranes in general) is not a sole indicator of hydration.

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