The Rim-to-Rim-to-Rim trip thread was getting contenous regarding possible mechanisms of developing hyponatermia which is low sodium levels in one's blood serum.
I posed some questions about hyponatremia to a double-board-certified, American College of Physicans member, hospitalist/internist M.D. (who I met on a backpacking trip in 1993 and married in 1997).
Summary of our discussion:
How could an extreme hiker/runner get hyponatermia?
Short Answer: By drinking far too much water.
But the kidneys are very good at maintaining sodium levels in a tight range with greatly varying hydration levels. Yes, you can drink so much water that in absence of any salt intake, you could flush your kidneys of sodium which would in turn deplete your blood serum of sodium.
She then went on to list numerous medical conditions that could also lead to hyponatermia which shouldn't apply to anyone thinking of a long hike much less a R2R2R.
Could a person develop hyponatermia from excessive use of electrolyte/runners drinks?
No. They could get volume-overloaded (especially with various (mostly serious) medical conditions) and that could create other issues, but since that water went in with sodium, it wouldn't deplete sodium.
Extra credit question from the chemical engineer in the room: If you took potassium salts to excess in the absence of sodium, could you develop hyponatermia?
Extra Credit Answer: Potentially if you were giving only potassium salts but all runners drinks and supplements that have potassium have a balanced amount of sodium. She wasn't sure, but suspected that serious, even fatal results (potassitum chloride is used in pet euthanasia) of high potassium would result before low sodium became an issue. i.e. you'd be dead of a potassium overdose before you developed hypothermia, but that was her guess - not a situation she's managed or could imagine developing unintentionally.
She then discussed how they put a bit of salt and a bit of baking soda in water when they do oral rehydration therapy because the water is absorbed more quickly that way. Sugars also help the water be absorbed more quickly. So I suppose if you WANT to induce hyponatermia, huge volumes of salt-free, sugar-sweetened water without any salt in your solid foods would be most effective. So don't do that.
I'm not doing 30-40 miles on free-range, low-sodium, steamed veggies and a few gallons an hour of pure water. I'll be eating a lot of solid food - a fair bit of it prepared/processed with salt, maybe a bit of gel, some runner's drink mix and lots of pure water to the point of peeing regularly. But HYOH, DYOD, EYOL.
(hike your own hike, drink your own drink, eat your own lunch)
But, as I've posted under the trip thread, I will be bringing micro-brews to share, so you don't have to BYOB. Nor fish - I'll bring the smoked salmon.