After suffering for a few years with rls, I mentioned it to my mum. She simply said eat more salt. So I did: I add salt to my daily breakfast omelette and my rls has 95% gone. The effect was almost immediate. My personal thoughts on this are : reducing salt in your diet is one of the easier "healthly" lifestyle choices to make. I certainly never added salt to food and don't eat much processed food so my sodium level is going to be on the low side.
Additionally, I exercise a lot and sweat a lot and wasn't actively replacing lost salts.
Finally, some research suggests you g potassium levels to maintain a healthy sodium-potassium ratio but if you're not consuming enough sodium then I 'd imagine extra potassium is not going to be used: perhaps give it a go if you can....