The Mythical Daily Water Requirement
8 glasses - that's what most people think they need as a daily requirement. Copious water intake is supposed to keep organs functioning properly, skin supple and body weight at bay. Nonsense! - say researchers from the University of Pennsylvania who conducted a study to test these theories (which will be published in the June issue of the Journal of the American Society of Nephrology).
We all know that our bodies need water, but nobody quite knows exactly how much. Let's take a look at where this misconception began, shed some light on water and hydration and look at some more realistic water goals.
Let's be clear on something right out of the shoot. Water is the hub of all chemical processes in the body and the king of all nutrients. We should be drinking it daily. But where did the 8 glasses per day gospel originate?
Dr. Frederick Stare suggested this theory in a book "Nutrition for Good Health" published in 1974 ("theory" being the operative word). The theory caught on despite its arbitrary origins and it has been speculated that bottled water companies are largely responsible for perpetuating the 8-a-day mantra.
Water Intake - Not Just From Water
Counter to what I've just presented, we actually DO need at LEAST 8 glasses of water per day. But here's the catch: This intake is satisfied not only from water intake, but also from other fluids, the food we eat and the metabolic processes required to break down that food.Juice and milk contribute to hydration and (surprisingly enough) so do caffeinated and alcoholic beverages. I probably don't have to tell you though, that alcoholic beverages are not recommended to help you meet your fluid requirements. Regarding caffeine - many people still believe it causes dehydration, however studies as early as 1928 have shown otherwise.
The fluid from food and its accompanying metabolic action alone can account for as much as 6 glasses of water! Water is the best fluid - no argument there, but don't get caught up in the absurdity of forcing down extra glasses of water if you have a coffee.
Water - Too Much of a Good Thing?
The more the better does not apply to even the mighty water. Consider that 31 runners in the 2000 Houston Marathon were treated for hyponatremia - a condition that can arise with excess fluid consumption, causing a dilution of sodium in the blood. This has prompted a revision of previous guidelines which have changed from "drink as much as you can tolerate" to "drink as needed, but do not exceed 800ml per hour"Estimating water needs
- There is a large variation when it comes to individual water needs. Those who are active have increased water requirements, especially if exercising in hot weather.
- As a baseline, 1L of water a day (about 3 glasses) should be fine for those individuals who are relatively sedentary.
- Increasing water intake to 1.5-2.5L/day (4-5 glasses) per day is a good idea if you are moderately to highly active, and drink a few gulps every 15-30 minutes if exercising in hot weather.
- If you are exercising for longer periods of time (going on a long hike, as an example), be sure to consume some salt when consuming large quantities of water.
- If fat loss is your goal, make water your primary beverage - aim for 75% of your fluid consumption, while cutting back on juice, pop and other calorie-containing liquids.
In Closing
Let's face it, most of us would probably benefit by drinking more water for the simple fact that it replaces other caloric and otherwise unhelpful fluids. Drink water whenever you can - try to have a glass with each meal, and consume it while you are exercising. Use common sense when hydrating during exercising - especially in hot weather. You need not, however count empty bottles, or stress if you fall a glass or two short of your daily "requirement".
References:
- Stare, FJ, and McWilliams M. Nutrition for Good Health. Fullerton, CA: Plycon, 1974, p. 175
- Grandjean, AC, Reimers KJ, Bannick KE, and Haven MC. The effect of caffeinated, non-caffeinated, caloric and non-caloric beverages on hydration. J Am Coll Nutr 19: 591-600, 2000.
- Tufts University Health and Nutrition Letter. New Consumption Guidelines for Water Sodium, Potassium. April, 2004
- THE PHYSICIAN AND SPORTSMEDICINE - VOL 31 - NO. 7 - JULY 2003. New Hydration Recommendations.
- Casa DJ: Proper hydration for distance running: identifying individual fluid needs. Available at http://www.usatf.org.
- Weinberg, A, and Minaker K. Council of Scientific Affairs, American Medical Association: dehydration evaluation and management in older adults. JAMA 274: 1552-1556, 1995
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49 Comments
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Created / Updated: November 2, 2011
I know I need lots of water. Probably relates to the amount of exercise I do, but I normally consume 10+ cups of water every day, usually more, and if I don't I feel like crap. (For cardiovascular exercise over 2 hours at a stretch, I take in electrolytes, too.)
ReplyGlad to read this. I've always been frustrated by the "drink more water" mantra. There've been precious few studies to back it up.
That being said, water should definitely be the beverage of choice -- when one is thirsty.
Replythat makes me feel better. after 8 glasses of water, its close to midnight and the water starts tasting weird... i have several other fluids throughout the day besides my 8 glasses of water, it makes sense to me to not require this much- generally, i've stuck to 4 8oz glasses plus whatever else i have ad that seems enough
ReplyPersonally, I drink at least eight glasses of water most days and usually more. I hate feeling like my mouth is dry, so I always have my trusty one quart water bottle to keep that nasty sensation at bay. Health is secondary in this realm.
ReplyMaybe it's my activity levels, but I've always felt the guidelines were spot on...for me. I like to sip throughout the day, and when I can't for whatever reason, I my lips get chapped and my skin gets dry. Then there's the thirst! And the fact that I feel more alert when I have regular glasses of agua.
I don't drink soda or anything like that, though, so it's not like I'm padding my levels.
ReplyGreat points, and great debunking, Mike.
Like Katie, I naturally drink a lot of water -- my mouth feels dry if I don't (and I notice that I get grumpy!) This has only been the case for the past couple of years though, and I think is tied in with taking more exercise. I get through about 500mls in the gym, and need a glass of water after cycling to work or home from work, but also seem thirstier during the rest of the day.
Anyone else find that exercise makes them thirstier in general?
Ali
ReplyMost people don't drink enough as it is or eat fruits and vegetables that have water inside....so for the general public "drink more water" is usually spot on.
ReplyMike OD - IF Life --
That's an interesting point. I'm definitely less thirsty when I've been eating a lot of salads or soups.
When I'm not being good to myself and relying on easy-to-store-and-grab dense foods (breads, snack foods, nuts, cheese, etc.) to meet all my calorie needs, I am thirstier.
ReplyWhile you have a point, some of us eat just fine and prefer to drink a lot of water. Most days, I eat several servings of vegetables at every meal and I still can go through at least two quarts of water every day.
ReplyThank goodness, I always thought the "8 glasses of water" challenge was similar to eating 72 Oz of steak at a sitting.
I'm sure it can be done, but dang it's a lot.
ReplyHaha.. Red - ever see a movie called "the great outdoors" with John Candy? Your post immediately reminded me of that scene where he devours the "old 96'er".
ReplyHe said 8 glasses, not 8 cups, which is a huge difference. How big is a glass? We know a cup is 8 ounces. A glass can be 6 to 12 ounces. If you drink 8, 12 oz, glasses, you could be getting 100 ounces a day.
Replywow, this makes me feel like I am drinking so much! I go through 4-7 32oz Nalgene bottles a day (depending on how hot it is). I am a distance running on my college track and cross country teams, so perhaps it's because of my high activity level (that and I do really sweat more than normal, I think)and my penchant for salty things. I've never really experienced any negative effects either. And I only drink water, and an occasional gator aid after a very hot and long workout.
ReplyGosh, what a cost to the environment that is... all those bottles... why don't you have one bottle and refill it?????
ReplySandy a nalgene bottle is just that a refillable bottle for liquids.
ReplyI always drank water according to urine color. Too dark? Drink more!
So I need 8 glasses a day.
ReplyThat's exactly what I do. I go by urine color usually.
ReplySame here. I run 5K every morning, so I generally drink about 32oz in a 90 minute span. The fluids run pretty clear at that point :) After that, I sip on another 32oz's for the rest of the day.
ReplyConsidering that they always say "8 8-oz glasses", that's really not all that much if you consider how big some glasses are. I fill a 1 liter Nalgene bottle with water and ice and sip on it at work and I fill it again to sip on while I drive home. Plus, I eat a lot of veggies and fruits that have lots of water in them, so I think I get plenty of water during the day.
I also drink diet soda, which I know isn't the best beverage option, but it's kind of obnoxious to me that the Coca Cola company now markets its beverages as "hydrating" and how they can help you contribute to getting your 8 glasses of water a day. I don't usually count soda towards my daily consumption of water.
ReplyPlease make sure you don't use your Nalgene bottle in the dishwasher or wash with really hot water. Also make sure when washing you are not creating deep scratches. Also make sure to be drinking fresh water (not sitting in a hot car for a few hours)--These hard plastic bottles are made with bisphenol A, which your body thinks its estrogen. For more info look up "bisphenol A" or "endocrine disruptors".
ReplyTrust me...I take care not to expose my bottle to very hot water, I never freeze it, and I don't ever leave it in a hot car or anything like that. I wash it with mild detergent in warm water and rinse it thoroughly to keep it clean, but it's just like any other polycarbonate plastic...keep it away from extreme temps.
ReplyI drink closer to a gallon of water a day.
Now, one might argue that that is way too much, but that is the level at which I feel good. Bear in mind, I'm still around 75 pounds overweight.
But drinking the water, I don't feel my eyes to dry out as much, my elbows don't need moisturizer applied hourly, my urine is not too dark and I just generally feel better. I do live in a dryer climate... and one that gets good and hot in the summer. I'll probably be drinking a bit more then!
I do count my green tea towards this consumption though.
ReplyI've heard that for every 25 lbs overweight that you are, you need to add 8 oz on to the 64 oz daily rule. So for you, drinking all that water is probably pretty spot on. I know that for me, it depends a lot on what I'm doing that day as well as whether or not I've eaten lots of salt. Anytime I eat salty things, I get SO thirsty and I tend to drink a lot more.
ReplyI've noticed that if I don't drink 2.5 to 3 liters a day, my gout rears up and whips my ass. I think it lurks in there, waiting and watching, and that one freaking time I only have 2 liters water, and then it strikes.
Sometimes I think it thinks I slept with it's wife.
Anyway, I drink a ton, but with a lot more activity these days it works.
ReplyI always have much better skin when I'm drinking a couple of litres of water daily. You can save a lot on moisturizers by drinking water - I'm sure Procter and Gamble, etc. would rather we not figure this out!
ReplyThe 8 glasses a day requirement was always bogus. Dr. Stare probably just estimated how much he drinks in a day and wrote that in. But think for a second. Do animals drinks a preset amount of water just because? No! They drink when they're thirsty and eat when they're hungry. Drink when you're thirsty is my rule.
Reply