Salt is a nutrient . The optimum amount per day in terms of how long you will live is between 1.5 and 2.5 teaspoons.
Am J Hypertens. 2014 Sep;27(9):1129-37. doi: 10.1093/ajh/hpu028. Epub 2014 Mar 20.
Compared with usual sodium intake, low- and excessive-sodium diets are associated with increased mortality: a meta-analysis.