When you exert yourself, you need to replace the water your body loses through sweat. Everyone (I hope) knows this. What’s the best way to do this? It has long been believed drinking large quantities of water is the answer, but this is not only wrong, it can be a fatal mistake.
You see, when you sweat, you lose more than just water. You also lose electrolytes such as sodium, sodium chloride, potassium, and magnesium. As you sweat away these minerals, your whole body starts to function differently; too little sodium in the body has immediate effects on the brain and nervous system, for instance.
When you start drinking water, you increase the amount of blood plasma in the body, which is good. The balance of electrolytes, however, is now quite wrong. Since the cells have low water content, there is an osmotic shift of water into the cells. Some cells will absorb so much water that they rupture; this is called cytolysis. Other cells will cease to function. When this occurs in the brain and nervous system, this is called water intoxication or hyponatremia. The most common symptoms are lightheadedness, confusion, apathy, nausea, vomiting, and headache; these will progress to seizures, coma, and death if over-hydration continues or is not balanced by electrolyte replacement.
How much water is too much? For an average person, it can be as little as two to three liters in an hour. If you’ve been exercising heavily, it can be less, because your salt and electrolyte balance is already wrong. It is possible to feel thirsty and actually be over-hydrated, as you can have too little water simultaneous with having low electrolyte balance. However, it is usually more important to consume water than to worry about water intoxication.
Anything that reduces your electrolyte content will put you at higher risk of problems… the higher the exertion, the higher the risk. In fact, it has been found that 18% of marathon runners and 29% of Iron Man finishers suffer at least moderate cases of over-hydration. Water intoxication is one of the most common causes of serious heat illness in the Grand Canyon. People working or even resting in high heat, people exerting themselves heavily in any weather (especially high heat), and people using drugs or alcohol are all at much higher risk of having problems. Working in a humid environment is also problematic, as you must sweat more to cool the same amount.
How do you maintain the right balance when you are dehydrated? The quickest way is to drink sport drinks rather than just drinking pure water. A more natural or simple method is to eat something when you drink, as most foods contain the proper minerals in enough quantity to restore the deficiency. Drink small quantities at a time rather than large quantities all at once. Stay hydrated, but within limits.
As with most problems, the solution is one of moderation. Drink, just don’t gorge yourself.
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Healthy thoughts,
Jeff
