I take 5-7g of salt daily in the form of manual supplementation. I eat a ketogenic diet so it's necessary to combat the diuretic effect of low-carb eating.
I feel like this study doesn't really do a good job isolating the actual changes that might have led to the improvements. How was salt intake determined? Was it controlled? Unless I am getting lost in the technical writing it looks like the results were based purely on urine output tests, not inputs.