Salt sensitivity is also far easier to manage, and its impact is limited to putting you over the top when shit hits the fan (eg: high-sodium diet can make or break you when you stray into heart-attack territory).
They found that the body cycle for salt is more complicated that thought before and "It is not only worthwhile reducing the amount of salt added to food for those who are ill - even the blood pressure in healthy individuals such as the Mars500 test subjects was reduced." [1]
https://en.wikipedia.org/wiki/MARS-500
[1] http://www.astrobio.net/pressrelease/4329/lessons-from-mars-...