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I drink a lot of water through a normal day, even when passive - about 7-9 liters. On days when I work out, I likely drink about 1-3 extra liters. Is there a rule of thumb for taking in extra electrolytes after drinking a certain amount of water?

1 liter = 0.25 gallons

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that is a whole lot of water to be drinking passively each day... you must be a very thirsty person :P –  moesef Mar 16 '12 at 21:45
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3 Answers

up vote 8 down vote accepted

Answer for When are electrolyte/sports drinks necessary?

It seems to me that you're basically asking 2 questions:

  1. Under what circumstances do most people need to drink sports drinks to recharge their electrolytes?
  2. When drinking large amount of water (it sounds like you drink up to 3 gallons per day), does a person need to make a special effort to replenish electrolytes?

I'll do my best to address both these questions based on the research I've done.

First of all, it's important to understand what "electrolytes" are. Essentially, an electrolyte is a charged mineral or salt. Electrolytes used by the human body include sodium, potassium, chloride, calcium, magnesium, and some others. Sodium and potassium are the electrolytes of which we generally lose the most when exercising (largely through our sweat).

Your body requires a certain amount of these substances to function. However most people consume more than enough of these electrolytes every day. Sodium in particular is something that most Americans get in much larger quantities than their bodies need. Although you lose sodium, potassium, and other electrolytes, sports drinks contain more than just electrolytes. They also contain sugar, and of course water. The general advice I've read is that if you're doing exercise for less than 1 hour, you probably don't need to worry about replenishing your electrolytes. You'll still have plenty left. If you're exercising to lose weight, drinking a sports drink after your work out may hinder your progress. You need to consume less calories than you burn, and the extra calories from the sugar in the sports drink may negate the extra calories you burned during your workout, resulting in little net benefit from your exercise.

On the other hand, if you're going to be running a long-distance race, or doing some other lengthy endurance exercise, you should be concerned about replenishing your electrolytes and rehydrating properly. You'll also need carbohydrates to keep you fueled. In this case, sports drinks may indeed be helpful.

For those running a marathon or long distance race, Livestrong makes the following recommendation:

Replacement Options When running a marathon, you must create an electrolyte replacement strategy. A variety of electrolyte replacement options is available. Examples include sports drinks, which contain both electrolytes and water to prevent dehydration. Gels also are available in small pouches and contain a concentrated amount of electrolytes. Jelly beans known as sports beans also can be used for electrolyte replacement. You can eat nutrition bars and sodium-containing foods such as pretzels, bananas and animal crackers. When choosing the best electrolyte replacement for you, consider portability and what will be easiest for you to carry with you on race day.

Frequency Marathon runners and training coaches Gary and Ellen Bloome recommend drinking one cup of an electrolyte-containing drink every 30 minutes during competition. Train with your electrolyte replacement drink of choice in order to ensure it will be sufficient to replace your losses. If you utilize electrolyte or carbohydrate-containing gel packs, the Bloomes suggest consuming one every four to six miles. If you utilize food or bars to replace electrolytes, break these into small pieces and consume some every 20 to 30 minutes.



Furthermore, the Wilderness Medical Society says this about endurance exercises:

The American College of Sports Medicine in its position statement, currently recommends a fluid intake during exercise of 600-1200 mls/hr. The fluid intake of most of the reported cases of exercise associated hyponatremia has been at the middle or upper end of this range challenging this as an appropriate fluid intake. A more realistic intake is likely to be 500-750mls/hr. Whether this fluid should contain salt as well remains unproven. Intuitively, it seems prudent to use a proprietary sports drink containing 20-30mmol/l of sodium if this is available, rather than just water.


As regards the water drinking question. About.com has this to say about water intoxication and electrolytes:

The kidneys of a healthy adult can process fifteen liters of water a day! You are unlikely to suffer from water intoxication, even if you drink a lot of water, as long as you drink over time as opposed to intaking an enormous volume at one time. As a general guideline, most adults need about three quarts of fluid each day. Much of that water comes from food, so 8-12 eight ounce glasses a day is a common recommended intake. You may need more water if the weather is very warm or very dry, if you are exercising, or if you are taking certain medications. The bottom line is this: it's possible to drink too much water, but unless you are running a marathon or an infant, water intoxication is a very uncommon condition.


However, the Encyclopedia of Nursing & Allied Health says:

Overhydration is an excess of body water that results when water intake exceeds output. Drinking large amounts of water does not typically lead to overhydration if the kidneys, heart, and pituitary gland are functioning properly. An adult would have to drink more than 2 US gallons per day (7.6 L per day) to exceed the body's ability to excrete water.


It sounds like you're drinking up to 12 liters, which is more than what the encyclopedia above seems to consider safe. So you might want to cut back. Also, it seems that drinking more than 1.5 liters in a short time (less than an hour) may also be dangerous, and you should be more conservative if you're on a low-sodium diet.

If you are drinking too much water, and your electrolyte balance is poor, some early symptoms may include nausea and vomiting, headache, fatigue, muscle cramps, spasms, and bloating. If you start to experience these things, stop exercising or doing things that would make you sweat, and try to improve your electrolyte balance. Eating a banana might be good, if you want to avoid taking in more liquid. Please note that the symptoms of dehydration are similar, however. Also cramps experienced during exercise are not necessarily caused by hydration or electrolyte problems.

Please note that I am not a doctor, dietician, or scientist. The above should not be taken as medical advice. If you're feeling like you might have an electrolyte imbalance, do not ignore your symptoms because of anything you read here. If you have further questions or concerns talking to your doctor and/or doing further research would be prudent.

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Amazing response. The thought of as little as 1.5 L of water in an hour being fatal is quite concerning. I think that I'll start mixing a bit of sports-drink powder into my water when I do cardio from now on. I can't cut back on my water intake since it is not artificial - I'm just always thirsty and I overheat easily. –  Haphazard Aug 24 '11 at 18:28
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This recent post on Science Based Running is relevant. The above answer is exhaustive, but the article covers some of the same ground with information from Tim Noake's The Art of Running. The author of the post also provides a brief analysis of some popular sport drinks.

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Welcome to F&N! Could you edit your answer to include a brief summary of the linked post? It gives readers a reason to want to click through to read the full post... –  Greg Aug 24 '11 at 20:09
    
I'll be happy to. –  pb2q Aug 25 '11 at 21:08
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Joshua Carmody's answer is pretty good but I'd like to add an ultrarunner's perspective. Proper hydration and nutrition are one of the keys to completing a race, and completing one fast, so we're fairly knowledgeable about what works.

The amount that Haphazard is drinking appears to be enormous to my eyes. However, as long as they are drinking for thirst then it is likely to be safe. The evidence we have is that, in normal circumstances, the thirst reflex is very accurate. I would also recommend using an electrolyte drink.

When performing an endurance activity then getting the water, electrolytes and sugar right is a primary concern. Opinions vary on whether you should exactly replace the water lost during exercise or whether it is actually possible to replace. The amount of water you can drink is limited by the rate your stomach can empty the water into your small intestine (the gastric emptying rate). This varies per person but is somewhere between 750mL to 1.5L.

The next problem is how much carbohydrate (sugar) to put in. What you drink needs to be between 6%-8% concentration. If the concentration is too high then the body will scavenge water from your bloodstream in order to make it between 6% and 8% and then pass it along to the small intestine. That scavenging process is not good because it will dehydrate your blood until the intestine returns the water.

The result is that you can only get about 200-300 calories per hour into the body.

The next problem is electrolytes. There are 4 that you need: sodium, potassium, magnesium and calcium. An electrolyte drink or an electrolyte/carbohydrate drink will have these in roughly the right concentration. The manufacturers compete on the science as to exactly what that concentration is but they're all roughly right.

When doing ultra-distance your body will start breaking down muscle in order to feed its calorie needs. Therefore, for distances longer than 50km most experts recommend that 1% of the concentration be protein in order to slow down this process.

Also, for exercises past a couple of hours you often need to supplement the electrolyte intake from your drink with salt pills.

Preventing dehydration and hyponatremia/hypervolemia (too little sodium/too much water) is a challenge. They have very similar symptoms and both can be fatal. This table from Karl King of Succeed! is the best guide I know of (I include it in my info for my race crew).

Guidelines:

  • For exercise up to 90 minutes, a well-trained athlete will not need extra water.
  • Past that point, an electrolyte and sugar drink should be used. - but mostly drunk for thirst.
  • For exercise past 4-5 hours, the drink should have slightly less carbohydrate and about 1% protein. For this distance, salt pills are probably required . This varies based on the athlete and the amount of water being lost. (A hot day requires more salt.)
  • When exercising, watch your urine output. If you don't urinate or if the urine is a dark iced-tea colour then you are probably dehydrated and need more water. If you start cramping then you need more salt. If your fingers or toes start getting puffy then you are retaining water and need more salt. In fact, in that case you should take some salt and sit down for 30 mins until you can urinate out the water.
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Great advice. That last guideline is something I'll look out for. –  Haphazard Aug 25 '11 at 2:10
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