Cynthia Leeder sent me this link yesterday: A description of “hyponatremia,” which happens when the body has too much water and not enough salt. An excerpt:

Ultra endurance events including marathons, triathlons and even the popular “eco-challenges” are seeing an increase in incidents. Last year, there were 30 documented cases of exertional hyponatremia, seven of which were admitted into the icu with intracranial pressure (icp). Although most of these occur with hikers, passengers on commercial/ private river trips have also developed hyponatremia.

When your salt balance gets out of whack, water can build up in your stomach and you can drink like crazy and never get hydrated. Oddly enough, the treatment for heat exhaustion — rest and fluid restoration — actually makes people worse if they’re suffering serious overhydration and salt depletion.

Prevention is the key.
Stay hydrated and nourished. Once hiking, keep a steady intake of water or electrolyte replacement drink and eat. I cannot emphasis this enough. Sport physiologists assume people are eating and therefore do not need commercial electrolyte replacement. The truth of the matter is that people don’t eat when they are hot, and they don’t eat once they become dehydrated and sick. Gatorade, which contains the highest sodium concentration, doesn’t even come close to the 35 mEq/liter/ hour needed to replace lost salt through sweat. What kind of food, my personal preference is salty snack food. This is not a time for power bars. Leave the health food behind. Junk food is great. Stock up. The rangers now routinely give out saltine crackers, pretzels and cheezits. Stay ahead of the sodium curve!

I’ve gone on a few summer hikes that left salt stains on my backpack’s straps. This is probably nature’s best signal that salt is leaving the body but isn’t going back in.

Read the whole thing — it might save your bacon.