If a person cuts out a lot of processed food when going on a low carb diet, they most likely automatically cut out a lot of salt naturally. A lot of processed foods have salt added for taste. So if a person goes to more of a whole food unprocessed food diet they may be reducing salt without realizing it. On a low carb diet the body does not retain as much fluid as on a high carb diet. When cutting out the carbs some of the first weight lost will be this excessive fluid. With the fluid excretion goes also the extra salt.

A common problem when people go on a low carb diet will be low salt. It brings on a condition referred to as the "keto flu" with flu like symptoms. It is not a flu at all but simply an electrolyte imbalance that will correct itself in a couple weeks. Or a person can just take a half teaspoon of salt and get over it. It is a lack of salt mostly (but can also be potassium and magnesium deficiency also).

Low carb diets usually need more salt added to the food, not less.

Wife and I salt to taste, which is quite a bit of salt. If you are hungry for salt, you likely need it.