The lst article link is written by a registered dietician who writes a regular column on nutrition. An excerpt:
HTML Code:
Healthy adults need 1,500 milligrams of sodium per day, and the upper daily sodium limit is 2,300 milligrams.
So, what are the symptoms when one lacks salt on a very hot, multiple-hrs. long summer bike ride?

All I've every felt is dehydration or bonking..both which I've found solutions over the years.

My brain is trying to wrap around the old past where there were more farming folk toiling in the fields. No doubt some of them might have fainted or had certain symptoms, but those were the days of no specialzied energy drinks,etc. I mean world-wide there were many farmers working many hrs. under hot sun/heat, surely their diets did not contain alot more salt than what we have today in our meals (if we blissfully ignore the sodium hidden in our food).

Anyway, I may sweat but not necessarily in same way as others.