You beat me to it. On the 100F+ days I was cycling in the Midwest heat wave I experienced, I was adding salt to my Subway sandwiches and fast food fries. When you drink six or seven liters of water per day, you'd better add salt. Hyponatremia does suck--a friend nearly died of it on a Tucson golf course. He stayed very well hydrated--too well, as it turns out.