Hydration and Beyond

  • Posted by a hidden member.
    Log in to view his profile

    Feb 17, 2007 11:58 PM GMT
    Perhaps we should discuss some facts and myths about hydration.

    Athletes can loose a lot of water and electrolytes in the course of a day, and need to take care to replace them. Popular culture (and this site) is replete with admonitions that everyone needs to consume some target amount of water each day. Eight glasses (or roughly two liters) is the most commonly-cited figure, and has achieved the status of religious dogma. However, there are frequent claims that drinking many times this amount has some benefit.

    In fact, there is no such magic number. The body needs to replace water lost through excretion, perspiration, and respiration. Anything in excess of that is excreted through urination, at the cost of loosing more electrolytes. The exact amount needed depends on body size, diet, climate, and of course activity level. So how much is enough? Fortunately, our metabolism has a very precise mechanism for regulating hydration, and triggers the thirst response when the body needs more water. Numerous clinical studies have found that thirst is an excellent guide for maintaining proper hydration. (For example, Phillips, et al. Physiol. Behav. 33:357-363)

    So where did the “eight glasses a day” rule come from? Nobody is exactly sure. The American Journal of Physiology asked a respected kidney specialist to investigate the matter . (Valtin. Am. J. Physiol. Regul. Integr. Comp. Physiol. 283:R993-R1004.) He made a comprehensive search of the scientific literature, surveyed other specialists, and sent out inquiries to popular press authors who write about the benefits of excess water. The results were a resounding silence. No scientific basis for the claim could be found anywhere. However, some empirical studies found that on average, healthy moderately active people consume about 2.5 liters of water a day, about half of which comes from the moisture in food and the other half from beverages. The National Research Council once made an estimation that the body uses roughly one ml of water for each (k)calorie consumed, and that most of that water is available from the moisture in the food. Somewhere along the line, somebody appears to have applied this to a 2000 (k)calorie diet but neglected to read the entire paragraph. Thus the myth of eight glasses a day (maybe) was born.

    What difference does it really make? As long as you’re getting enough, can there be too much of a good thing? Actually, hyperhydration can be quite dangerous and has resulted in a few well-publicized deaths. But there can be harmful effects short of death. Endurance athletes, military recruits, and hot-climate workers have been found to suffer relatively high rates of water intoxication. (For examples: Frizzell, et al. JAMA 255:772-774; Klonoff, et al. JAMA 265:84-85; O’Brien, et al. Mil. Med 166:405-410; Noakes, et al. S. Afr. Med. J. 91:852-857.) Again, the amount required to produce harmful effects depends on a lot of variables. But one frequently implicated contributor is a loss of electrolytes from excretion and perspiration. Another is extreme dieting. And by the way, Party Animals, another contributor is the use of Ecstasy. Anyway, those who find themselves consuming much more than a couple of liters of water a day should probably be adding electrolytes to their beverages.

    Somewhere in the nebulous area between “enough” and “too much” water, there still appears to be room for some of the health benefits that have been claimed for hyperhydration. However, if there are scientific studies demonstrating these benefits, they are awfully hard to find. If you know of one, please post it!

    Actually, I found a couple of such studies, but the effects were not dramatic. People who drink lots of water (about 2 liters a day) had slightly lower rates of some kinds of cancer than those who drank only a little (less than 1 liter.) (N.Engl. J. Med 340:1390-1397.) But the study was controversial (N. Engl. J. Med. 340:1424-1426; and 341:847-848.) Drinking cold water burned a few extra calories, from the energy needed to warm it to body temperature, but at best that would burn off the equivalent of one slice of bread a day. (J. Clin. Endocrin. Metabol. Dec. 2003.)

    Currently, the most credible recommendations that I’ve been able to find are: 1) Let your thirst be your guide. 2) Coffee, juice, tea, soda, and the like ARE just as good as water for hydration (not necessarily good for your diet, though). 3) If you find yourself needing more than a couple of liters per day, use electrolyte replacements. 4) Don’t worry about meeting any arbitrary target amount of water.

    If anyone knows of any actual evidence (not just claims) of the benefits of consuming excess water, I’d be quite interested in learning about it.
  • UStriathlete

    Posts: 320

    Feb 18, 2007 4:55 AM GMT
    I have heard from several MD's the recommended water intake is half your weight in onces. plus what you have listed is very common information.
  • atxclimber

    Posts: 480

    Feb 18, 2007 7:17 AM GMT
    Hmm, I always just assume as long as I'm drinking when I'm thirsty and urinating regularly and it's relatively close to colorless, I'm alright.

    As for electrolytes and exercise, everything I've read suggests that different people sweat different amounts of salt. After I go for a long bike ride I'm like a walking salt lick, so I've been drinking the Clif Shot energy drink, which is saltier than most. One downside is that the salt content actually makes it less viscerally quenching when I'm riding... I don't have that "I just climbed a rough hill, I take a deep draught, and it's super-satisfying" feeling.

    Plus, I'm getting sick of the "Crisp Green Apple" flavor, but it takes me forever to go through a jar since I mix it at 50% their recommended strength, which I find overpowering.

    Here's a hydration-related question: oftentimes, like a ride I did today, after doing a lot of short standing steep-hill climbs, my calves will start to get cranky and cramp, even if I've been drinking a lot of this stuff; plenty of sodium, enough carbs, and certainly enough water. What other factor -- other than just me pushing myself too hard, which I don't think I'm doing -- could cause muscles to start cramping like that? I stretch reasonably pre- and post-riding, too. Should I be mixing my beverages differently, or drinking more, or less, or something?
  • Posted by a hidden member.
    Log in to view his profile

    Feb 18, 2007 1:38 PM GMT
    "Anything in excess of that is excreted through urination, perspiration excretion"

    If that were true, which it is not, then we would be in a constant state of dehydration whereby mental alertness would suffer, fatigue would ensue and our bodily functions would start to cease.


    "Numerous clinical studies have found that thirst is an excellent guide for maintaining proper hydration."

    Thirst has been identified as a latter sign of "dehydration" and the "thirst response" is the bodys warning sign that you need to consume more fluids or bodily processes will start to be affected.

    "What difference does it really make? As long as you’re getting enough, can there be too much of a good thing? Actually, hyperhydration can be quite dangerous and has resulted in a few well-publicized deaths."

    This is pure hype and misreporting. majority of the well publicised deaths, as yuo yourself have cited, were as a result of someone with extreme dehydration, extreme dieiting or in an extreme situation are you starting to see a picture emerging here? They were either not consuming sufficient minerals and vitamins from food or consumed vast quantities of water in a relatively short period of time. Its hardly surprising this occurred.

    "Anyway, those who find themselves consuming much more than a couple of liters of water a day should probably be adding electrolytes to their beverages."

    Massive assumption here!!!!!!!!!!! On the one hand you are saying diet has a factor to play in your argument earlier and now you are totaly ignoring this fact and saying that you need to "supplement" your electrolyte intake when there are reems of studies that show quite clearly that majority of these faddy supplements are totaly a waste of time and money. They have only been to show of benefit in those suffering extreme dehydration.

    This brings me back to the other thread that you seem to be rebuting my comments on. If you are dehydrated and consume vast quantities of water then the very process of osmosis means that the fluid in the cells that absorb the water will be of a lesser consentration and therefore leeching of electrolytes will occur. Hence if the water is consumed over a very short period of time then problems will ensue.

    "Drinking cold water burned a few extra calories, from the energy needed to warm it to body temperature, but at best that would burn off the equivalent of one slice of bread a day. (J. Clin. Endocrin. Metabol. Dec. 2003.)"
    No one ever claims it will make an enormous difference but now multiply that by volume and over a period of a week its not huge but then again a drop of 2% body fat is not huge either so you see the puzzle starts to fit together.


    Coffee, juice, tea, soda, and the like ARE just as good as water for hydration

    Since when has adding natural diuretics and toxins been good for you when it comes to hydration!

    You seem to be good on collating studies but have a restricted understanding of the validity of the information, the environment and purpose of the study etc.

    Im not claiming to be an expert in this and hence wont quote rafts of studies quite simply because so many are not fit for puprose as they do not fit the exact specifications of the question in hand.

    To argue that hyperhydration is bad for you and responding with studies based on extreme circumstances is almost as bad as those that based their understanding on the harmfulness of Ephedrine based on those idiots in the sauna that is so well publicised. Pure unrelated unsubstantied hype. (and no I am not supporting ECA).

    Im not after having an argument for arguments sake here and if you are a research scientist who can come back with a conclusive study on the impact of hyperhydration in a healthy individual who is not placing there body under extreme stresses then maybe it would be a meaningful discussion.

    If not its as good as saying meat is bad for you based on a study for a specific purpose that shows cooking meat for consumption gives you cancer, trust me there are hundreds of them out there!
  • Posted by a hidden member.
    Log in to view his profile

    Feb 18, 2007 2:51 PM GMT
    It is true that caffeine is a mild diuretic. And soda is far from nutritious; the sodium benzoate reacts with the acid to make benzene, a carcinogen, and the phosphoric acid leaches calcium from bones, for starters. However, the diuretic effect is weak enough that it only gets rid of part of the water contained in the soda or coffee or tea, so there is a net hydrating effect. I have heard that for soda and coffee, the caffeine gets rid of ~1/3 of the water. So, it isn't totally worthless for hydration.

    I also think it is unfair to label coffee or tea a toxin. The caffeine is a drug, but another drug in its class (methylxanthines) is used to treat asthma (theophylline). While it has its risks, it is by and large extremely safe. Tea in particular has been associated with a number of health benefits, in particular postive effects on possibly preventing dental cavities and an anti-cancer effect from the anti-oxidants in it. I don't have the time to chase down my references, but I think it suffices to say that coffee, tea, and soda can all be hydrating, and coffee and tea are generrally healthy and safe in moderation.
  • atxclimber

    Posts: 480

    Feb 18, 2007 5:46 PM GMT
    As far as hyperhydration being bad for you, while death due to water poisoning is certainly rare, it seems safe to say, for example, that drinking water or a beverage with lower sodium content than your sweat while exercising intensely is going to lead to electrolyte depletion.

    Most energy drink manufacturers have tailored their drinks to encourage athletes to drink while riding; a recent study pointed out that tart or citrusy flavors cause people to drink more, as does electrolyte content (i.e. salt), and it's no coincidence that Clif's flavors are Lemonade, Crisp Green Apple, and Cran-Raspberry (and they're salty.) From that I infer that their data says the average athlete would benefit from drinking more while exercising. Or they're desperate to sell as much drink mix as possible. Or both, I guess.

    And I remember reading that a recent study concluded coffee was the average US resident's #1 source of antioxidants. Oh yeah, it was this:

    http://www.physorg.com/news6067.html

    It doesn't actually argue that coffee is the densest source of antioxidants, though, just that it's the #1 source given estimated per-capita consumption (it would be dates if US residents ate the same volume of dates as coffee.)

  • Posted by a hidden member.
    Log in to view his profile

    Feb 18, 2007 9:30 PM GMT
    Personally, I don’t like any of the carb-based sports drinks while on a ride, unless they are greatly diluted. Someone recently gave me some samples of a brand called “electromix” that I kind of like. It’s got no carbs and just a faint lime flavor. When I was on a trip to Japan, the sponsor kept us supplied with some stuff called (I think) “Pokari Sweat.” It tasted… exactly like sweat collected off someone’s body and chilled. Eeeww!
  • atxclimber

    Posts: 480

    Feb 19, 2007 12:10 AM GMT
    Hmm. Do you consume any carbohydrates while riding? Your muscles only have enough glycogen capacitance to last you about an hour of serious biking, and after that your body's going to burn some fat... but also muscle tissue. Plus, those are nowhere near as high-bandwidth energy sources as good old blood sugar. If I were to do a 4- or 5-hour ride and not consume any carbs during the ride I think I'd bonk pretty hard.

    I usually mix the Clif stuff at 50% in one water bottle and my second water bottle is just straight-up water, and I drink the one with the mix first.

    Pocari Sweat - ha! I've never had that stuff, but those Asian beverages can be hilarious. Demi Soda Apple is one of my favorites. Oh yeah, and Milkis! The kind of gross-sounding and gross-looking soda that seems to have milk in it... but I think it tastes great, anyway.
  • Posted by a hidden member.
    Log in to view his profile

    Jul 11, 2007 9:03 PM GMT
    bfg1:

    ""Anything in excess of that is excreted through urination, perspiration excretion"

    If that were true, which it is not, then we would be in a constant state of dehydration whereby mental alertness would suffer, fatigue would ensue and our bodily functions would start to cease."

    actually that is true, when the body has too much water it sets off certain chains of action which reduce the production and effects of vasopressin and AntiDiureticHormone (And some other punk hormones). Too much water throws off the balance of the body and there are biochemical processes to correct that.
  • UStriathlete

    Posts: 320

    Jul 15, 2007 4:38 AM GMT
    check out www.medioncorp.com

    really great information and has a hydration calculator and you cann ask a Dr. questions.

    seems like good product too. order some myself!

    can_du says he uses the product.