You are able to use potassium chloride instead of sodium chloride (table salt) to regenerate your water softener. Potassium chloride is a bit more expensive to purchase but as the advantage of not adding sodium to your diet. This may be important to some customers who have health conditions that are made worse by a high sodium diet. This includes some kidney and cardio-vascular conditions.
It is worth noting that potassium chloride can melt when it is wet which makes it form a bridge in the salt tank. You can deal with this by only filling the brine tank to halfway so that you can keep a track of how it has gone down after regeneration.