除了白毛女，好像还未听说谁盐吃少了出问题：）

quote from internet:

The National Heart Lung and Blood Association reports that 500 mg is a safe daily minimum intake of sodium. This amount will be enough to maintain the bodily functions that require sodium. In an average temperate climate, a normal adult may be able to thrive with as little as 115 mg of sodium each day. Because most foods contain at least a small amount of natural sodium, it is difficult to drop below the minimum recommendation even on an extremely low-sodium diet.