[lotsofmangos]

If you are just drinking water and not eating, then this could be a problem, but then you have other problems anyway.

[kiiski]

If we are talking about installing these to rural parts of Africa, having to eat more may be a valid consern.

[lotsofmangos]

We are talking about trace quantities of salts though. You could get around any measurable problem by passing the water through a large box full of pebbles. Also, water is for agriculture as well as drinking, so this should increase the stability of food supply anyway.