Low Salt Levels in Hikers

A study from Kaiser Permanent in California shows that hiking for several hours without taking salt can send you to an emergency room. When you exercise, you sweat, which contains much less salt than blood does, so you lose far more water than salt, which causes blood levels of salt to rise. You have to lose more than two pints of water by sweating for the salt concentration in your blood to rise high enough to make you feel thirsty.

If you exercise for a long time and take in water without also taking salt, your blood salt level drops, so you are not thirsty and you feel no need to drink. This causes you to become dehydrated and you may become nauseous, vomit, and feel dizzy and you can convulse and pass out. To prevent low-salt syndrome which blocks thirst, take salt and water when you exercise. Eat salty nuts or drink sport liquids that contain extra salt. Drink before you feel thirsty because you do not feel thirsty until you have lost more than two pints of fluid, and then it is too late to catch up on your fluid loss.

HD Backer, E Shopes, SL Collins, H Barkan. Exertional heat illness and hyponatremia in hikers. American Journal of Emergency Medicine, 1999, Vol 17, Iss 6, pp 532-539.

Checked 8/31/08

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