Hydration 101: How Much Water Do You Really Need? | Chris Kresser
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Hydration 101: How Much Water Do You Really Need?

by Chris Kresser

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Eight ounce glasses of water, eight times per day: this has been the water drinking mantra pushed by health professionals, beverage companies, and popular media for decades. From the number of people sipping on water bottles on a constant basis, it seems like the “drink more water” message is getting through. But is this message accurate? And where did it come from?

It may surprise you to learn that there has never been any scientific evidence to support the “eight by eight” doctrine when it comes to proper hydration. The first recorded scientific endorsement of a water intake recommendation appeared as a brief footnote in 1945, when the Food and Nutrition Board of the National Academy of Sciences published its Dietary Guidelines. (1) And like many other nutrition recommendations, it appears that individual needs for water vary widely, and 64 ounces of pure water every day may actually be too much for some people. (2) So how do you determine how much water you need as an individual?

There is no evidence to support the recommendation to drink 8 glasses of water a day.Tweet This

How much water do you really need?

There’s no question that adequate hydration is important, as water is a critical nutrient, but the eight by eight guidelines are a gross oversimplification. There is no universal requirement for water intake, and your needs will vary widely based on age, gender, body size, health status, and physical activity levels. Numerous environmental factors, such as high temperature and humidity levels, also influence water needs. (3)

It is difficult to estimate an exact amount of water needed for an individual, so thirst should be used as a general guideline for most individuals. In other words, if you are thirsty, drink, and if you’re not thirsty, don’t force yourself to drink simply because you believe it to be a healthy practice.

Additionally, the eight cups a day recommendation typically does not account for the water content of food. Many Paleo staples are surprisingly high in water; besides just fruit and vegetables, foods like yogurt, salmon, eggs, and potatoes are about 75% water, and four ounces of broiled salmon provides about one half cup of water. (4) If your diet is full of water-rich fruits, vegetables, and animal products, you may not need as much liquid water as you think. And if you’re eating soups or broths, that volume should certainly be counted towards your daily fluid intake.

Let thirst be your guide

Thirst is a sufficient indicator for most people of hydration status. From an evolutionary perspective, thirst has done a pretty good job of enabling us to survive as a species. While many believe that thirst is an indicator that a person is already dehydrated, this claim has not been substantiated by any research. (5) Thirst actually begins when the concentration of blood, an accurate indicator of our state of hydration, has risen by around two percent; experts generally define dehydration as beginning when that concentration has risen by at least five percent. (6) So while thirst is a good indicator that a drink would help maintain good hydration, it doesn’t necessarily imply dehydration.

Exceptions to thirst guiding hydration might include athletes engaged in exceptionally strenuous activity, when dehydration is far more common and adequate rehydration is essential to athletic performance as well as good health. Drinking plain water can improve performance in endurance exercise, but there are further performance improvements when carbohydrate and electrolytes are added. (7) Sodium should be included in fluids consumed during exercise lasting more than 2 hours, and is beneficial for aiding rehydration for anyone engaged in moderate activity. (8)

People with health conditions that affect their thirst, such as diabetes or kidney disease, may need more precise estimations of fluid needs on a daily basis. Excessive thirst is a symptom of hyperglycemia, among other diseases, and not necessarily an indication of dehydration.

If you find yourself having constant thirst despite drinking regularly, you may have a serious condition that needs treatment from a medical professional. Again, individual needs will vary greatly, so pay attention to your own health.

What should you be drinking?

Pure water is probably good enough for recreational athletes engaged in mild to moderate activity. Those doing intense training or those who sweat excessively, however, will need electrolytes in addition to water, and possibly even sodium tablets. Sodium is essential to avoid hyponatremia, a serious condition caused by a lack of salt in the blood, leading to water imbalance and water build-up in the brain. (9) Therefore, sodium is one of the major electrolytes that is essential to include in a rehydration beverage following strenuous exercise.

There are many great natural alternatives to commercial sports drinks for replacing electrolytes during and after strenuous exercise. Bone broth is full of minerals such as calcium and magnesium, which can help with muscle contraction and relaxation, as well as amino acids for improved muscle and joint repair, making it a great choice for athletes. Coconut water has a good mix of electrolytes and simple sugars to aid in sports performance, though extra salt may need to be added to some brands that are lower in sodium to optimize rehydration.

Homemade sports drink recipes can be found around the web; a great one can be found on Wellness Mama’s blog. Fermented pickle or sauerkraut juice is another great way to boost hydration, especially for those who need the extra sodium and electrolytes. An added bonus of drinking these fermented juices is that they also contain probiotics to aid gut health. Even just adding a pinch of sea salt to your water bottle should be sufficient to aid in rehydration after a trip to the gym.

Take home message: Drink what you want!

The best advice I can give when it comes to water consumption is let your thirst be your guide, and adjust your fluid intake depending on your lifestyle and environment.

If you are relatively sedentary, live in a cold climate, don’t sweat much, or eat water-rich foods, you probably don’t need to be drinking eight cups of water a day. There’s no evidence to support those recommendations, and forcing down excess water throughout the day is not only unnecessary, but can cause damage if done too frequently. For most people, the body is its own best guide.

What is your favorite way to rehydrate? Do you have any beverage recommendations that I didn’t mention in my article? Share with us in the comments section!


Join the conversation

  1. If a person has not drunk enough water their entire life per the amber color of urine, can they restore normal hydration to the body by drinking sufficient water daily?

    This week I went into a plasma donation center and they told me my veins were too small and weak to donate, but said to go back home and drink a half ounce per my body weight daily. I began and noticed the light color of urine, which made me realize how much damage I may have caused my poor body these 50 years.

    What results have you seen with those in my situation who have repented and began a good water drinking regimen?

    • The color of your urine simply represents the concentration of salts in it. If your urine is lighter, it means that there is a higher concentration of water.

      Since (a portion of) the extra water you are drinking every day is in your urine, this may indicate you do not indeed need that much water.

      However, I’m not a doctor, so take this with a grain of salt.

  2. Chris,

    I am curious to hear what you think of water needs in a person with only one kidney. I am otherwise healthy but I only have one kidney because I donated one to my sister-in-law. The transplant center advises me to drink 1/2oz of water for every pound I weigh.

    Is this really necessary?

  3. So animals who only drink when they are thirsty must be really bad off , since they are doing it all wrong ! They even eat only when they are hungry ! My cat had food and water available at all times and never got overweight . My friends cat get fed a certain times of the day and got fat.
    Perhaps we shouldn’t listen to people who don’t know what they are talking about and listen to our bodies . It served humans very well for 1000s of years, just now we thinks we have to ask “the experts” how to survive and it seems to me now we don’t do that well anymore.

  4. I have been taking triamterene for years for hypertension. Now that I am over 70 my aging kidneys are showing up on blood tests as compromised. The first thing my doctor told me to do is to start drinking 60 oz of water a day. So if you take a diuretic you definitely may need more water. I’ll certainly try it.

  5. So if I’m drinking Reverse Osmosis water do I need to put mineral stones in the bottom of my water container to add minerals back in?

  6. I agree with the article in that everybody’s circumstances are different. Weather and activity level are the determining factor. To me drinking before getting thirsty makes as much sense as eating before getting hungry. It will lead to overweight health issues. Our ancestors acted on nothing but thirst and hunger as motivators and I believe that the body knows best. The question should be more about how much attention are we paying toward the sensation of thirst. I know when I am busy at work as a first responder, I don’t always have time to pay attention to my thirst. I will change that by always having water readily available and to make the time to dink when I feel thirsty.

    • So my 79 year old mom barely drinks any water cause she claims it makes her pass urine but she can’t move her bowels so what’s the deal?

      • She is dehydrated and it is causing her bowels to be constipated. And yes she is going to urinate more frequently when drinking more water but that is perfectly okay and it’s good for your body. It helps to rid your body of toxins. Please encourage her to drink!!!!

  7. If I don’t put electrolytes (Nuun tablets) in my water when I exercise (even for less than 30min) I will start breathing heavily, I will want to vomit and faint. If I hadn’t found this out, I would not have been able to get in better shape. I don’t know why this is such a problem for me though, if I drink too much water (especially when exercising) I actually feel a lot worse. I came to the conclusion that water is not that hydrating by itself…

        • You need more salt in your diet. low blood pressure can ce the result of low sodium intake. And if you eat too much salt and not enough water you will have high blood pressure and you would need to increase water intake so you excrete excess salt and normalize your high blood pressure. This is what my Dr. told me. Try himalayan pink salt and never table salt, that happened to me and my soduim levels were low now i feel more hydrated and i also thought water was enough but that is not the case. I stopped eating as much salt as i always did and there is where the symptoms began so everything went back to normal when i increased my salt and kept drinking about six or seven glasses of water a day.

  8. I decided to ‘get healthy’ about a year ago and started drinking 2 quarts of water daily and in about 3 months I was practically bedfast. I thought I was losing my mind and was ready for the bone yard (so to speak). My doctor found that my sodium was in the critical stage and that I could have suffered seizures,
    a heart attack or stroke at any time. I had to go into the hospital for saline solution IV’s and was there for 3 days. So drinking the recommended amount of water (2 quarts) a day can be very dangerous indeed.

    • Twid, something is seriously wrong with your thinking. There is no relationship between drinking a half gallon of water a day and sodium levels. Water does not deplete your sodium. Your failure to ingest adequate sodium was your error; not drinking water.

      • that’s not completely true – it sounds like he was diluting the concentration of sodium in his blood creating a pseudo-hyponatremic environment (leading to his symptoms). He didn’t need more sodium, just less water.

  9. While this information is ‘well intended,’ and as my Grandmother used to say, the highway to hell is paved with good intentions. Everyone’s need for water AND the nutrients needed to absorb that water, can be different, but what is not stated here, is that a lot of people have no idea that they need water because their sense of ‘thirst’ isn’t working correctly.
    Drugs, including common over the counter ones, age, lifestyle, and/or or less than perfect health, can interfere with ‘thirst’ perceptions. If someone is looking for a ‘rule of thumb’ to determine their need for water or other fluids, the color of the urine is a better rule, than ‘thirst.
    If the urine is very light yellow or clear, the body is probably OK, If it the color of apple juice, you are seriously dehydrated, not matter how you ‘feel.’ If it reaches a brown coloring, you need to get to an Emergency Room right away.
    Do not ignore the medium or darker yellow color, because continued dehydration can permanently damage your kidneys, and it also indicates a lower than normal blood volume. A low blood volume coupled with a blood ‘thinner’ (anticoagulant) can spell disaster from what would seem like simple bumps and/or bruises.

    If a person drinks pure water, their body will not be able to absorb (use) it, because other nutrients like calcium, potassium, and sodium, must already be present to allow that water into cells where it is needed.


      • I’d like to know what type of water you’re using now and if you’re convinced that it’s only the water change that’s affecting your sense of being “run down.” I came to this page specifically because I found your comment in a search because of this issue of minerals removed by reverse osmosis water.

        The RO dealers claim that the minerals in water are both minimal and difficult to assimilate and that sufficient mineralization can better be obtained by proper food sources, though that’s rather bogus, failing to recognize the travesty of farm land neglect that (you might think my opinion perversely conspiratorial) I think is deliberate because there has been a deliberate attempt, years ago, to destroy the small farms of good and conscientious farmers with corporations which, I think, are controlled by boards that are illegally manned by the same people who man the boards of the pharmaceutical and medical corporations so that they will have a strong supply of people fed with worthless and overly processed food that doesn’t contain the nutrients for good health.

        Yes, I know it’s hard to believe such a sinister situation could possibly develop but I think it has and was very deliberate and the government, via the FDA, is in full collusion.

        It’s even worse because of the revolving door between FDA management and Monsanto, which is clearly intending to not only attempt to own and control the seed companies of the world but to convert what hasn’t already been converted to GMOs.

        Everyone should understand that the corn crop in the US comes from a GMO seed that is not only saturated with a poison that kills weeds but will produce corn that is non-fertile and will not grow, so that the farmers (now mostly corporate farms who took control of farms in the 80s through criminal (yet legal) machinations and manipulation of the markets and money to put America’s food production in the hands of a few who are not interested in provinding good quality food.

        It’s not only hard to believe; it’s hard to imagine that the evil was intentional and Machiavellian. I’m convinced it was and that the mass of people in this nation are a woefully misled and misguided by the media and educational establishments, which have shaped the government because of the people behind them.

        I encourage you to search and listen to “Norman Dodd On Tax Exempt Foundations” (YouTube) and listen to it several times until you get a good enough handle of the information to be able to inform casual acquaintances because you’ll send the video link to your friends.

        • I didn’t proofread and made too many mistakes. I’d appreciate it if you delete the above post along with this one and I’ll repost after you do. Thank you.

    • So, are you suggesting the reverse osmosis water is likely to not be utilized by the body as well as good quality tap water?

      By good quality, of course I *mean* good quality, knowing that much tap water around the country and around the world is inferior and has high levels of impurities and most people don’t test their water at the tap.

      Thanks for your reply.

  10. My personal belief is that today’s generation is not drinking enough simple clear n clean water these days, my water must go through reverse osmosis . The seniors of today are the worst offenders I have found. They come into our emergency rooms diagnosed as severly
    dehydrated only after the main issue for the real emergency has been established. Seniors having strokes must be monitored on how much clear clean water they are consuming.
    My Mother was severely dehydrated last month until a IV was given to her containg fluids. In just two days her appearance changed dramatically! So, when caring for ‘hard headed’ seniors it best you consult your doc, then go online, find a site geared for seniors who have some specific health issue then be clever in getting them to drink the planets best drink in the Galaxy … ‘cool clear wonderful water’, it may save your loved ones life !!!

    • You don’t get “reverse osmosis” water through an IV. You get salt water aka normal saline. That is why people perk up so much after IV fluids. If you gave someone fluids with too low of a salt content you can actually cause brain swelling. So you’ve actually contradicted your own point.

  11. the saying ‘if you wait till you’re thirsty, you’re already dehydrated’ is as logical as ‘if you wait till you’re hungry to eat, you’re already malnourished’…if you’ve lost about 2% of your bodily fluid balance, you’re thirsty, 5% yes you’re dehydrated.

    ever wonder why humans feel they’re the only ones who have to drink copious amounts of water and ignore their innate thirst cues unlike animals? does your pet dog or cat need to drink to a schedule or carry a pet-sized water bottle?

    • Yes, funny that, I was thinking just the same thing myself – I have had a bloated stomach – can’t get to the bottom of it then I thought a couple of days ago about the amount of water, tea & coffee – liquid I drink – a huge amount! Not necessary & just habit.

      If you think about it, if you are busy at work you can’t be making endless drinks or pouring yourself yet another glass of water.

      Children at school – they have breakfast, a mid morning snack (before Maggie T a 1/4 pint of milk) at 11, lunch with water or weak orange squash. A snack once at home & possibly a drink before going to bed.

      Pets too – absolutely! My dog’s bowl (shared by the cat) is only ever half empty & I change his water maybe every couple of days – when it looks empty or has bits in it!

    • Give you older loved ones salt. It will make them thirsty. I suspect that low salt causes many to not drink enough water.

      And no, I didn’t ever believe the doctors who claimed salt is bad for you and happily heard the “Dead doctors don’t lie” doctor say, “Salt is good for you and won’t hurt you. Season your food to taste.”

      I *know* the medical industry has done great harm to us. If you doubt, think of appropriate keywords,search and learn.

      Like “pharmaceutical fraud” or “ama crimes” or “cancer cures” or “cancer conspiracy” “lies of the medical industry”

      Experiment. enter “magnesium constipation” and consider why webmd.com is the first entry with a warning of the side effects of magnesium and then then enter “magnesium constipation cure” and see all the sites that tell you magnesium is the number one solution to constipation.

      Understand that Google isn’t serving you; they’re serving their own pockets and the billions of dollars they make on advertising is enhanced by cooperating with the wealthy who make their money off the backs of everyday people.

      Spend enough critical thinking skills on Google and you’ll see why some people’s slogan is “Google is evil.”

      Search “fbi pedophilia” and you’ll only see the FBI as the good guys. You’ll have to get very specific with “owen decamp bonacci pedophilia fbi” to discover that the FBI threatened 28 kids that “you’ll go to prison and stay there the REST OF YOUR LIFE if you testify” against the elected representatives that were molesting the kids–but even then you might have to sift through many pages to find the facts. Google is government’s friend, not yours. You should have been able to find it with “fbi threathens pedophile victims” but if you try that, you’ll only find the FBI as the hero, but if the FBI was really the hero, there wouldn’t be 800,000 children abducted every year.

      You won’t find the truth by “fbi threatens 28 kids” either.

      Do the search “conspiracy of silence pedophilia” and watch the video and start searching. The more you search, the more you’ll think, “this can’t be real; this is like a nightmare.” Wait until you see it’s worldwide and the authorities everywhere cover it up. Then ask yourself if we really need atheists with no morals running the government.

      And don’t think I’m suggesting that the men like Obama who say “I’m a Christian” are telling the truth.”

      Our nation is in worse shape than you can imagine and the media is our greatest enemy. They’ve pretended that there is an adversarial role with the government and that is a total lie. The unelected mean who rule the elected men rule the media also.

      • Gary, you and I seem to be very like minded. I don’t believe that these thing are theory anymore. If you don’t mind my asking, where else do you comment? Are there more of ‘us’ out there?

    • Just like people, pets’ sense of thirst diminishes as they age. In the wild, we assume that animals drink when they are thirsty; but it must be remembered that aged animals are rare in the wild.

  12. When I started intentionally drinking more water – and not just when thirstly – I started feeling much better, and my digestion improved significantly.

  13. Let’s see. I drink when I’m…wait for it…thirsty! Honestly. To all the personal trainers, nutritionists, etc. that say if you wait until you’re thirsty to drink, you’re already dehydrated. What kind of a statement is that??? Well, duh. That’s why I’m drinking a glass of water, cuz I’m dehydrated. I remember my mom (and then me) going on diets as far back as the 50s. All diet books came up with this 8×8. #1–it was supposed to fill you up so you wouldn’t eat more food. (Didn’t work). #2–they wanted you to stay hydrated while cutting back on calories for an extended period of time. Electrolyte balancing come to mind. Oh and BTW, back in those days, you never stayed on a weight loss diet longer than 2 weeks. You then ate normally for a week and back to dieting. Unlike today, where you’re encouraged to stay on a diet until you lose the weight. If you’re dieting for an extended period of time, I could see the 8×8 making sense. And exercise. And heat from the weather. And to flush fiber.

  14. I take 25 mg. of hydrochlorothiazide for hypertension and have taken it since I was a teen in combination with other meds. I am now 71. I am very active and box and workout every week. I have noticed that since I have stepped up my workout it takes longer for my muscles to recover. I do stretching exercises but they don’t seems to work with my muscle recovery. Could it be that I am dehydrated from the combination of my workout and the diuretic? I do follow the 64 oz. rule and eat yogurt, fruits and vegetables.

  15. Dear Chris,

    what is your opinion about the recommended liquid intake done by the EFSA for men (over 14 years of age) to drink 2.0L a day and women (>14 yrs) to drink 1.6L? See: http://www.efsa.europa.eu/en/efsajournal/pub/1459.htm

    Their advice came after extensive literature studies and is the official recommendation by the European Commission. The recommended advice is now being advocated to the general public as well as health practitioners.

    Look forward how you see this advice vs your position as to let thirst being once’s guidance.


  16. This is great information that should be more exposed. I too was a victim of the “water solves every problem” myth. Constipated, headache, nausea, overweight, back pain, allergies? Drink more water!! Errrr! What ever happened to just drinking when you’re thirsty? I used to force myself water and wonder why I craved salty foods so much. There is so much push to drink more water these days and yet so little about how we can flush out all the minerals and vitamins our body needs to survive! Thanks for the article Chris.

    • I agree, I think we drink far too much water, I have cut way back, I drink a glass a day these days.

      Plus a mug or two of coffee, a glass of wine every now and then, plus plenty of fruit, and some vegetables, and moisture from the air. My urine is still a lightish color and I don’t go to the bath room all day and all night.

      I met this nutritionist who got me thinking on this. Drink when you are thirsty he said, it makes sense to me.

  17. “For repeat urinalysis after adequate hydration”….Why is it that i need to repeat urinalysis after adequate hydration? I am worried about this, do i have any disease?.please reply me..thanks

  18. Eighty years ago when I was in high school I studied Chemistry. Mr. Chapman, our instructor, made it clear that sodium chloride is a compound and that sodium is a ‘metal’ that combines with chlorine to make sodium chloride, our common table salt. It makes me cringe when I see sodium and salt used interchangeably in discussions in nutrition. You would never really eat sodium; you’d die. But we need common table salt. (I know there are various kinds of ‘salts.’ Potassium chloride is one of them.) So instead of agreeing that we mean sodium chloride when we say sodium, why don’t we use the word ‘salt and agree that we mean sodium chloride?’ What the body with the sodium and chlorine ions in the blood and organs is something else. Outside of the body we take table salt. I have a salt shaker on my table, not a sodium shaker.

  19. I’ve always wondered what made the 8 by 8 rule and how it was proven. It never made sense to me that everyone big or small young or old with these masses of different body types would “need” the same amount of water. I’ve also wondered about purity of that water. I know a lot of filters going to a diatomaceous earth to purify and get clean water on a larger scale. Is there an over purifying of water as well? Is it good to have some minerals in your water for your body?

    • Clark have you ever heard of oxidation? Battery acid? Aspartame? If not I suggest you do some research. Diet coke is one of the worst inventions in the history of humanity! Check your magnesium levels 🙂

    • Leg cramps are stopped by mustard and water, if you drink coke,Pepsi or any other drink sweetened with sugar or sweeteners your asking for leg cramps. Regular yellow mustard stops leg cramps in their tracks. Water helps prevent leg cramps. Any simple or complex sugars add to the problem.

  20. I am 13 weeks pregnant, and everywhere I go, everybody tells me to drink, drink, DRINK! My GP, my OB-GYN, even my husband always reminds me of that (he loves his water). I am aware of the importance of water and I really am trying to meet the daily norm, but it makes me sick. I feel too full, a lot of discomfort, my belly hurts and it makes me go to the toilet so often. At first I thought something was wrong with me, but today I told my husband maybe I was not made to drink so much. I can do half of it, like 4 glasses, but I never manage to do more. Even this feels more than I would like to. I don’t work out at the moment, I take my folic acid for the pregnancy and I eat my veggies. Trying to be a good girl 🙂 Any advice?

    • Racula, the ‘fullness’ can be easily experienced with drinking tap/bottled water. The same was resolved for me when I tried Kangen Water for the first time, it tasted so good that i couldn’t stop! Drinking it will actually make your body wake up! The hydration it provides is much more efficient due to the molecular restructuring. Kangen water is also full of antioxidants and, unlike the traditional chemically treated tap water was a real solution for me. Well renowned medical practitioners such as Dr. Hiromi Shinya recommends drinking this water. He’s a founder of colonoscopy and examined over 300,000 patients both in the US and in Japan. I’m sharing this because it has made a massive difference in my life on many levels and it might be of help to you. If you want any more info email me: [email protected] And all the best!

        • Really? I like to hear people’s discoverys to improve health, and to do new research. That is how you learn !!!

          • If you knew anything about the product that was being pushed, you would understand. Any product worthwhile doesn’t need to be sold under a pyramid scheme.

      • Another promo of a product. I am getting to the point of not eating of drinking anything that does not exist in nature. Eg. honey instead of sugar, full cream milk instead of low fat. Same thing goes for Kagen water or whatever that is. For the most part anything changed by humans is messed up and has some side effect.

    • The reason why your on tells you to drink water is preeclampsia, this disease can kill you and your baby, please keep track of swelling and you blood pressure while pregnant, if you become hypertensive, seek medical attention.

      • I would disagree here… especially ‘diet drinks’…and especially if the drinks are pasteurised etc. Nothing can totally replace real water and fresh fruit/vegetable juice from a juicer! So stuff from boxes/plastic bottles, coffee etc. actually does the opposite. It is all oxidising and adds to the free radical damage.

    • I add a tablespoon of a Himalayan Pink Salt brine mix to my 32 ounce glass of drinking water. I have been do this every morning for over a year. The restructured water and salt combination provide optimal hydration. Plus, Himalayan Pink Salt has over 84 minerals.

  21. I wonder if you have read Waterlogged by Dr. Tim Noakes.

    If not I think you should.

    You may re-evaluate your opinion of the need and benefit of electrolyte drinks during exercise.

    On top of that it contains an absolutely breathtaking evolutionary view of thirst and bipedalism that alone make this book an essential read.

  22. “Think back to biology.” I took biology in college — one semester 50 years ago. I was a music major. So now I just sit at my computer and happily soak up the knowledge of others such as yourself — and not infrequently display my ignorance of the whole subject. 🙂

  23. Thanks, DePaw. No wonder I’ve felt absolutely water-logged on the few times I’ve actually tried to do the 8 x 8 thing! The part about “produced by the metabolism” is interesting. I would never have thought of that as a source of hydration.

  24. Fibre Menace has a great bit on the origin of the ‘8 glasses a day’ thing.

    Page 48:
    “A person weighing 70kg [155 lbs] requires at least ca. 1,750ml [59oz] water per day. Of this amount ca. 650ml is obtained by drinking, ca. 750ml is the water contained in solid food, and ca. 350ml is oxidation water.” This quote is from ‘Human Physiology by Schmidt and Thews.

    The book goes on to say that 1750ml is about 7.5 ‘glasses’, and was rounded up to 8 glasses for the slogan. But this includes water in food and produced by the metabolism, so only 650ml or 2.5 ‘glasses’ actually needs to be drunk.

    Merck Manual of Diagnostic and Therapy is quoted saying “a daily intake of 700 to 800 ml is needed to match total water losses and remain in water balance”

    This is only 3 ‘glasses’ and includes drunk water and that within food too!

  25. From what I’ve read, the 1945 Food and Nutrition Board recommended 1 milliliter of water for each calorie consumed, which worked out to about 64 ounces of water per day. BUT the rest of that statement: “. . .but most of this quantity is contained in prepared foods,” somehow got lopped off, and the 64 ounces has taken on a life of its own. As with everything else, there are clearly a variety of needs for a variety of individuals, but Chris, you are right to question the conventional “wisdom” of 8×8 per day for everyone.

  26. Thank you for clarifying this Chris. I sometimes hear from clients that they cannot get enough ice water. Is this indicative of something in particular? Thank you for your time.

  27. My husband is an active 75 ad never feels thirsty or hungry.. he does not like water either. I have real trouble getting him to drink at all. I need to make him cups of tea several times a day. He complains about a dry mouth and brown urine. One day last august he was left alone at home for 10 hours, and when I returned he was in a state of collapse – he had neither eaten nor drunk all day. I do not know how to persuade him to take care of himself!!

  28. Dear Chris, a very interesting article this is! I was wondering what your view is in respect of the work of the following people:
    – Dr. Corinne Allen (http://www.brainadvance.org), doctor and proponent for natural health for over three decades, as well as an international researcher. – her 4 part lecture called ‘Brain on Water (part 1’ …2, 3, and 4) is available on youtube.
    – Dr. Batmanghelidj, M.D. (author of many books, one of which is ‘Your Body’s many cries for water’)
    – or Dr. Barbara Wren (www.natnut.co.uk), author of ‘Cellular Awakening’
    And there are many more…

    To comment on what you’ve said, i absolutely agree that the ‘optimum’ water intake does depend on the person’s diet, size, genetic disposition or how much exercise we take or if they have a condition. The question is water just water? And what water provides the best and most effective hydration and is most helpful to your body? I’ve recently invested in a Japanese innovative technology by a company called Enagic that manufactures home units which not only filter your water whilst preserving the minerals, but which also turn your ordinary tap water into a micro-clustered, ionised, alkaline and highly antioxidant water called Kangen Water. Due to its unique properties the water acts as a free radical scavenger (as it’s negatively charged), alkalises your body and provides instant hydration as the molecules of the water are much smaller comparing to ordinary tap water. This kind of water is available by so called ‘healing waters’ or waterfalls where exactly the same process happens naturally. But how many of us live by a waterfall these days? 🙂
    I’ve done a lot of research and my due diligence for the past few months, still reading books and scientific reports and the findings are just incredible, including people’s testimonials and so I love sharing this with people as optimum hydration is a necessity.
    If anyone wants more information feel free to contact me or visit http://www.kangenwateredinburgh.com to sign up for a free newsletter and request a free e-book. There’s a great website put together that explains the rationale behind the technology.
    password: scotland

    I look forward to your comments! 😉

  29. Great post, Chris.

    Now that it’s hot outside, I really like sipping iced green tea throughout the day – some caffeinated and some decaf. I find if I don’t have something to sip with me, then hydrating is out of sight, out of mind, and I don’t get hydrated enough. I don’t think I’m overdoing it now, but I’m quite sure there have been times when I’ve underdone it.

    Several people commented on filtered water. I wonder if you’ve done a post on that. If so, will you please reply with the link, and if not, might you consider doing one?

    I found this link, which rates the various ways of filtering water: http://bit.ly/OeOnf7 It would be great if you would comment on its accuracy.

    Many thanks.

    • Susan,
      I have the whole house system (installed May 2011) that received the “A” grade on your website link. I am very happy with it and know that my water is much improved. I didn’t really study the rating method employed by the website but they didn’t compare very many systems with each other. I had a plumber install it for me under my house (crawl space) and I change filters in it quarterly and annually (different filters). After 3 years or 300,000 galloons I will replace the main unit.

  30. I definitely have something wrong with my thirst signals in that they don’t really exist or alert me when I need to hydrate myself until I am dehydrated. I never feel thirsty. I was having dizzy spells from dehydration and still never felt thirsty. I have to make myself drink water and rely on the color of my urine to tell me if I’ve had enough water or not.

    I do notice that the more water I drink the more I want to drink and the less I drink the less I want to drink… maybe when I drink more of it I activate my thirst signals somehow? Not sure, but it has always been a mystery to me why I’m never thirsty and on the rare occasions I do feel thirsty I can’t believe it. Guess for the most part I am getting enough, but again, even when my urine is darker yellow and I know I’m not drinking enough water I’m still not thirsty.

    • I seem to be losing my thirst too. I’m only 31, not 90. I would like to know why I am losing it. In the past, oh, month I’ve probably been thirsty a dozen times.
      The thing is, I know my mouth is super dry, but drinking water isn’t quenching. I have to force it down.
      I’ve got celiac disease and seem to have issues with sulfites.
      I really want to know what’s causing me to loose my sense of thirst.

  31. I’m convinced that the SAD and lifestyle (i.e. too much light, stress, and not enough sleep) are responsible for the bulk of our health problems (any arguments?). The diets and lifestyles in retirement/nursing homes is often sub-optimal in that regards (poor diets, prescription diuretics, poor sleep, etc). Those living a low-stress life and eating a traditional diet can probably rely on thirst as an intact cue. People living a crappy lifestyle are probably dehydrated, and for those people swilling a couple litres of water will help temporarily, but only by correcting diet/sleep, etc will their systems correct itself.
    I think Chris’ recommendations should be taken in proper context…sort out your lifestyle and you probably don’t need to carry a Nalgene from your belt loop.

  32. This line of discussion reminds me of the “sip all day” versus “drink as you want” at periodic times through the day. This whole hydration system back-pack craze has me in stitches. I see children and adults engaged in light to moderate activities with a tube hanging form their mouth all day. I often wonder if this has an effect on the thirst-signaling system in our body. Do their bodies “forget” how to be thirsty or are they always thirsty being accustomed to a “steady drip” .. I much prefer to carry a canteen or water bottle and drink as I am thirsty.

  33. A dentist told me that people on drugs such as anti-depressants are a group that do need to drink regularly, but in small amounts at a time to keep the mouth moist. Otherwise, they are likely to end up with either gum disease or fillings. This is because the drug alters the saliva flow, and not enough saliva changes the bacterial content of the mouth. Whichever bacteria change determines the gum/teeth status.

  34. Hi, Chris, great article. My question is about well water. When we moved here 20 yrs ago we put in a reverse osmosis system because our well water (the well is over 200′ deep) often has a slight sulfur taste. Now I worry that we should have been drinking the well water straight in order to get the minerals. Which is more beneficial/safer – to drink the well water, get the minerals and risk the bacteria/possible pollution, or to filter the well water and get the minerals somewhere else? We are out in the country but there is a huge military base nearby that could be polluting the groundwater. thx.

  35. Thanks so much for your take on the water recommendation.

    I love kombucha as an ‘electrolyte’ drink while hiking in the hot sun. I’ve been able to do the same hikes without getting dehydrated that I had suffered on while drinking lots of plain water. One bottle of kombucha to one bottle of plain water seems to do the trick for me.

    • Kombucha is awesome! It saved my back when I had a bulging L4-5. Reduced inflammation, gluten-free and McKenzie Press-Ups…..those saved my back. No surgery. I am on my way in a few to get Kombucha at the Farmers Market. Trying a new flavor: Pina Colada.

      Thanks for your reply

  36. I wonder how much water our paleolithic ancestors drank? They certainly didn’t have nalgenes. I bet our ancestors ran more dehydrated than we think.

  37. We have a whole house water filtering system and to me the water just taste better because it is so clean tasting. Besides when I bath or wash clothes none of the toxic get into my skin or my clothes. I am all about fresh clean water.
    Great article…I too drink when I am thristy, some days more then others. Go figure.

    • Could not agree more about filtered water. Mine is an Aquasana whole house filter. Stripping out the flouride, chlorine, and who knows what else. The water taste is excellent. It’s just a shame I’m also using that to flush the toilets. 🙂

      • @Rufus, It is good to have it in your toilets too Rufus. If your toilets have treated water in them the Chlorine will evaporate into the air as the water stays exposed to the air. You then are breathing the chemicals instead of drinking them. My unit is a whole house Aquasana also, I am very happy with it.

      • The Aquasana system does not remove fluoride, also be sure to check if your municipality uses chlorine or chloramines to sanitize water because the system will only reduce chloramines not completely remove them.

  38. I have a whole house water filtration system and I keep glass water bottles in the refrigerator. When I go out of the house for work or errands I carry water with me. Throughout the day I sip water and carry my water into resturants when I go out to eat.
    Water filtered with a quality system and consumed on a regular basis (not to excess) is what works best for me.

  39. Thanks for the important comment on elderly patients. My mother had absolutely no thirst reflex and we took her to the ED more times than I can count to be rehydrated. One doc said: her urine looks like Cabernet. I asked her primary care doc if we could set up a drip at home (she had a skilled caregiver) and he rolled his eyes at me. What a waste of time, resources…and life.

  40. Great article Chris. I have one suggestion for anyone that is ill or looking for an ideal and exact method for keeping their body properly hydrated. Get a refractometer and measure your urine brix. This is a measure of your urine concentration and it can be an extremely helpful guide in determining fluid intake. I would even go as far to say that it may be one of the greatest health tools available since proper hydration has so much to do with overall well being and optimum body functioning. Sometimes the body’s own fluid intuition can be off and a refractometer shows you how to optimize it.

  41. As I get older and older …. 94 now …. I am more and more concerned that my body may not be telling me when to drink . As a result I drink mostly when I am thirsty as Chris says. I take no medications of any kind, prescription or OTC. Therefore, there is no influence there. The engineer in me tells me to note what makes me thirsty. I find that excessively sweet things and escessively salty things will make me very, very thirsty. For me, there is treachery in foods. I get apprehensive when eating out, or anywhere when others are doing the cooking since excess salt easily hidden, and it will make me very thirsty hours later when I get the AHA! moment. Yes, Chris, listen to your body and don’t try to fool your body either.

    • Your 94 and clearly doing what right. Keep it up. That’s fantastic. I have a 93 year old in my house and she eats and drinks what she wants which doesn’t include pop Coffee tea orange juice tomato juice and water. I know I won’t live to be 93 but clearly not overthinking everything and no Internet use has aided alot of elderly people to live long healthy lives. If any of us younger folk even make it close to their age, it will be because they chose to eat and drink in moderation and avoid every fad that passes by.

  42. Chris,
    Thanks for a nice perspective. I already printed out some of your info to two patients this morning. Currently reading Waterlogged by Tim Noaks which goes down that rabbit hole a bit more. You can hear him interviewed by Ben Greenfield a couple of times as well. Your efforts are greatly appreciated.

  43. Often I add some flavored stevia to my drinking water. Most days, I drink about 6 8 oz glasses and that seems sufficient. The stevia just makes it feel like a treat and does not add or take away fromt he value of the water, to the best of my knowledge (google Sweet Leaf or Wisdom Natural Brands for info on the flavored stevia). If anyone knows a good reason why not to use it, please comment.

    • “If anyone knows a good reason why not to use it, please comment.”

      I think it’s a good idea to get used to the fact not everything we eat needs to taste sweet. Take some time to enjoy bitter, sour, spicy, etc.
      I know for me, any time my food paradym shifts, my palate needs a little time to shift also. Just like shifting from hot showers to cooler showers, there is an ajustment period and for me the stevia would prevent the transition to being able to enjoy fresh lemonade with no sweeteners in it.

  44. I feel like when I was pregnant, I needed a GALLON of water a day ;o) This is a really interesting article. Thank you for all the research you provide!

  45. One last thing: I’m also finding the folks have lost their thirst – meaning they’ve gotten so dehydrated that their body doesn’t even signal thrist anymore… until they get properly hydrated and then their thirst mechanism comes back. I’ve read and experienced myself that by the time I’m thirsty I’m already on my way to being dehydrated. So for myself and the recommendation I give my clients is to drink a minimum of 50% of their body weight in water a day, split into 3 portions to be drunk over a period of time between meals – before breakfast, between b’fast and lunch, and between lunch and dinner. Minimizing fluids before bed. Add another 16 ounces for any coffee, alcohol or (God forbid) soda, which I also work to help people wean off. Add another 32 ounces for strenous workouts. This rule of thumb
    seems to work really well for everyone.

    • I don’t get your rule of thumb. I weigh 152 lbs. Should I drink 76 lbs of water a day? Or do you mean take one-half my weight in pounds and drink that number of ounces of water?

      I take Chris’s point that a universal rule such as yours is not really necessary. But, I think people need to be sensitive to the possiblity that as individuals they may be prone to dehydration and their thirst mechanism may not be functioning well enough to rely on it for prevention. Those people should adopt a rule of thumb.

    • Hey Shaya, it seems you’re trying to equate the folks who frequent Mr Kresser’s blog with the overweight, undernourished, junk food eating general public. I’m willing to bet a fresh organic glass of coconut juice that anyone who frequents this blog is pretty far from dehydation.

    • I totally appreciate your opinion, which comes from direct experience. Thank you very much for sharing your wisdom. I am an example of precisely what you describe.
      I need water and lots of it. I only discovered this recently, that i was so dehydrated and had no real thirst and yes hungry all the time.
      So basic, yet so overlooked.

  46. As a nutritional counselor, I am finding that many chronic health issues are relieved with proper hydration, and that most of my clients are coming in dehydrated. I think this relates largely to the amount of diuretics people are drinking – everything from coffee first thing in the morning and many times continued through out the day to soda and other concentrated sugary drinks to the cocktails and wine they drink in the evening. People are quite dehydrated, and often need to drink more than 8 glasses of water a day to make up for the loss they are experiencing through the other beverages they are drinking. There is a downward vicious cycle of becoming dehydrating, losing energy and reaching for the quick energy of coffee or soda or sugar and then becoming further dehydrated. So I don’t take hydration lightly in my practice, in fact water and proper hydration throughout the day is one of the first places I start. Especially with high blood pressure, urinary issues, energy issues, mood issues, digestive issues, sleep issues, chronic pain, etc. It’s all related to chronic dehydration in my opinion. Certainly one needs to know how to properly hydrate their unique body, but I’m suprised to read that you shrug it off as an important player in the health issues people are facing today. I really appreciate your blog and often recommend it to my clients, but this article makes me a bit nervous. Our primordial hunter gatherer ancestors may have been properly hydrated through food and the occasional sips of water from the spring, but today’s busy, coffee and wine fueled society is a different animal that needs, in my opinion, to really watch their hydration vigilantly according to their diet and lifestyle.

    • I think you have your information wrong. While you could certainly argue that they do not make you more healthy, coffee, soda and sugary drinks are not diuretics! That really is an old, unfounded belief. Please check the research because it shows that only in excessive amounts does caffeine have a diuretic effect. Also, high blood pressure is not related to chronic dehydration and while adequate hydration is necessary, be careful pushing too much water on those with high BP. If they have an undiagnosed cardiac condition, that can cause congestive heart failure.

      • Thank you! I was thinking the same thing and have always believed that the 8 by 8 water concept was nuts. I have always been one to drink about half the recommended amount of water and my urine has always been very pale yellow and my BUN and creatinine has always been good. I’m a nurse and don’t have time to pee much less drink.

  47. Both coffee and tea are diuretic, this means they will dehydrate the body.
    Also if you feel hungry drink a glass of water as the brain confuses thirst for hunger.
    Fruit juices can’t substitute for water either as the body has a hard time properly metabolizing sugar. To correct the reaction to this, the body has to surrender water from the extracellular fluid.

    • Yes, it does naturally. Typically, coconut water contains 2-3 times more potassium than a banana and always includes a small amount of sodium as well. During exercise, these are typically the only two electrolytes your body really needs. Extended exercise sessions do place extra stress upon the body which then depletes other electrolytes, but overall, potassium and sodium are the two most important to be consumed during exercise and should always be consumed together, if possible. Their uptake in the body is synergistic and works much more efficiently if they’re paired.

  48. Thanks for another great article Chris, every time I read one of your articles I see the clear concise execution of common sense and scientific backing that makes your work very informative and it’s a great recourse for my clients (im a PT) aswell as me. With the regards to the water consumption I would definitely agree and say that the body and mind are the best indicators as to whether we need more (or sometimes less). I’ve seen water consumption almost cure feelings of empty thoughts and depression over night , it truly is the mineral of life 🙂

  49. @Carol – I understand that you do not really benefit from drinking a freshly juiced drink unless you consume it with a saturated fat as you are unable to absorb the minerals etc properly without the fat. Is this correct?

    • @Marrat. Where did you get that nonsense from, WPF?. You dont need fat to absorb most minerals expecially electrolites, like sodium potassium, etc, its just share bro science. TO consumer sat fat with juice to get your minerals absorbed its like adding protein in your water to get water absorbed :D. Can believe ppl right such things. You may absorb better some fat soluble vitamins like carotene consuming with fat, but not minerals.

      • The slam against Weston A Price is unsubstantiated. If our nation would have followed the health wisdom and science of Dr Price ( and the organization bearing his name) we would be the healthiest people in the world .. We have gone an opposite direction and are asa result -the least healthy.. I suggest you brush up on his and their writings and research.

        As far as “juicing” goes – where did one get the idea that it is even good for you.. yet another infommercial-based decision. Too many late nights awake in the hotel room?

        Juice= concentrated fruit ( w/out any fiber) = SUGAR ; which is THE main culprit in modern disease. (And that’s not even considering the other poisons)

        All modern fruit is bred for high sugar content, so unless you are picking/buying wild fruit ( like wild blueberries), it is a losing battle to try and show the health advantages of fruit in general.

        Good starter article on it-

        “If the govt says it’s good for you… RUN !”

        • Ummm…juicing for most people means vegetables with a very very small amount of fruit. What are you talking about?

          • Gotta watch those Weston Price sycophants, they’re zealous!

            There is far more to juicing than people who don’t juice know. The non-juicing community always uses a bottle of high fructose commercially prepared crap as the straw man.
            Funny how many anti-juicers take vitamin suppliments. What’s up with that?
            Lastly, Mark Sisson is my most favorite nutrition and exercize guy, but even he drinks unfiltered tapwater. I sure don’t.

  50. Also wondering about adding something like Emergen-C to water. I take a hot yoga class and started adding that in. Does it have everything I need or should I make a homemade mixture?

    • You could instead just eat an orange or two since Emergen-C does very little to your system except severely overload it with vitamin C. It’s good that vitamin C is water-soluble so you excrete anything your body can’t absorb, otherwise you could get C-vitamintosis extremely quickly due to build-up in adipose cells.

    • Actually, if you read the label of Emergen-C, you’ll see it has Fructose listed as the first ingredient, and 6 grams of sugar total. I’d avoid it for that reason alone. I’d just drink water.

  51. I was wondering about Brad’s question too. Regarding drinks, I do drink water upon rising but I’m also trying to have one fresh juiced green drink – all veggies with 1 granny smith apple per 2 servings.

  52. No quibble with the gist of this, but some huge caveats:

    In the exercise guide “Body by Science”, was written by Dr. Doug McGuff, M.D., an emergency room doctor. In a discussion about adequate hydration when exercising, he had this paragraph:

    The importance of adequate hydration is seen daily in emergency rooms throughout the world, particularly with elderly patients, whose thirst mechanism is impeded. A common tipping point in their becoming ill is inadequate hydration, which impedes the ability of the bloodstream to deliver sufficient oxygen to the tissues. Dehydration results in a constriction of blood volume to the point where they can no longer perfuse their tissues with sufficient oxygen, causing them to become acidotic. Once this happens, the metabolism becomes almost glycolytic, producing lactic acid. At the same time, a consequence of acidosis is a drop in blood pressure, resulting in acute sickness. Many such elderly patients who arrive at emergency rooms from a local nursing home look as if they are dying, but after the attending physician administers a liter of IV fluid over the course of two to three hours, they awake, completely alert, and appear completely well.
    [end quote]

    My Dad, an active and healthy 89-year old, has had several spells that were scarey, and led to discussion of whether activities like driving might need to be curtailed. They are thoroughly controlled by a recognition that he needs to drink water even though he is not thirsty. My then 87-year old father in law lay near death (so it seemed) in an emergency room, with no treatment for hours, until the Sunday morning crew showed up at 8 and gave him an IV drip. By 10AM he was back from the dead and raring to go. Elderly people should not trust their thirst mechanism, especially if they are popping all kinds of pills as most of them are.

    A failure to understand this is putting a needless strain on emergency rooms, and adding to the woes of our seniors with an easy as pie fix available for no cost. Understand that the thirst mechanism can be faulty with age and medications.

    To avoid cramping if an athlete is prone to that, early and plentiful hydration is needed starting well before the exercise and thus well before the body is sending thirst signals. This is good too for osteoarthritis if exercise brings on pain or stiffness, as hydration adds a little extra bounce to the cartilege.

    • I agree that relying on thirst is not always adequate (though it should be under ideal circumstances). I think modern, stressed out humans are often a bit out of touch with their bodies’ signals. I, for one, often find myself drinking very little water for a few days because I am not thirsty. When I notice this and make myself drink some extra water, I almost always feel better.

      • I third that idea as I know from personal experience when I was studying during university that the long hours, focus and stressed lifestyle barely ever made me think of drinking. Relying on my body’s signals simply wasn’t good enough, as again we are in general as a society today completely disconnected from our body’s signals, nature, each other, etc… I would go daily on a juice box! (yes hard to believe when I think back now) for days and not think anything of it. It wasn’t until I took drinking water seriously and properly “rehydrated” my body that I knew what it meant to “need” water and have the body ask for it specifically each day.

        So yes, I agree that the numbers are artificial and each person will need a different amount, but I don’t think the importance of getting high quality water daily can be over emphasized for optimal health.

        • If you are “normal”, “healthy”, thirst is the best indicator to measure if fluid intake is needed.

          However, as Chris pointed out, if you are very physically active or suffer with chronic health conditions, your own body may not be the best judge or form of measure regarding fluid intake.

          Even fluid “input/output” ratio may not be valid if the person is retaining water within the body (abdominal distension, foot/leg edema, etc.)

    • What do you all think of Hexagonal water? I have been researching the “Vitalizer Plus” (VitalizerPlus.net) for a while and it intrigues me lots. It is a wee bit pricey, but if it’ll feed my body more nutritional water, I may go for it. That vs juicing? Ur thoughts, please.

      I have “Body by Science” downloaded on my Ipad and am in the process of reading it. Very good read.

  53. I completely agree with the ‘drink when your thirsty’ statement. Typically I drink water that has gone through a reverse osmosis treatment. I add essential salts back to this water using commercially available products like Concentrace. Do you think salts should be added to RO water? Is there validity to the claim that because RO water has virtually everything removed it is more reactive and leaches your body of essential salts?

    • I do RO and I also do concentrace minerals, but I DON”T do the concentrace minerals BECAUSE of my RO filter.

      Most of the minerals in the tap water cannot be adsorbed by or bodies, and some of the TDS in tap water is caused by metals you don’t want anyway. One serving of greens will give you more bioavalable minerals than several days of tap water.

      The whole RO/mineral scare hocum is led by idiots that think flourine is beneficial to your health. We know better than that.

  54. I often wonder if high consumption of tea (orange pekoe) or coffee or fruit juice is considered part of the necessary daily water intake. And, does it count for ultrasounds when they ask you to drink volumes of water?

    • All of them contribute to the total volume of fluids you take in during the day. Remember, however, that fruit juice contains sugars.

    • I was wondering the same thing Brad. That is how I have always gauged my hydration levels. I have heard that urine should be very light yellow ideally. Totally clear means too much water, but very concentrated yellow means not enough (unless you’ve just taken a round of B vitamins).

    • If your urine is clear, you’re actually overhydrated. The general consensus for proper hydration is urinating once every 60-90 minutes and/or your urine is ever so slightly yellow, neither clear nor fully yellow (and not radioactive yellow due to excreting excess water-soluble vitamins your body cannot absorb). However, be aware, foods and drinks can also influence urine color directly, regardless of fluid intake.

      You can use the following chart as a (very) rough guide: http://flowingdata.com/2012/02/17/urine-color-chart/ . “Optimal” typically looks like a faint yellow.

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