I read somewhere that the salt-hypertension link only occurs in about 5% of the population. The rest of us simply pee excess salt out (assuming we drink enough fluids).

Over a period of a few days, I can usually tell when I'm low on sodium. I tend to have problems on long, warm rides; if I'm not paying attention, I can run low on water AND salt, and that sucks the joy out of a ride really fast. It's hard to process enough water and salt through the digestive tract in a short time. I should mention that I sweat heavily, and I sweat lots of salt; I'm the only person I know who can have salt rings on a high-vis jersey when it dries.