We use salt on Alizonne - so we are actually prescribed salt tablets. i also use salt in the veggies we have for dinner and with tomatoes if i have them for my lunch salad. So i second Weasey's salt advice.
Given you are doing this before surgery, you might want to ask your GP to run some blood tests and check your potassium levels and thyroid. There are rare vlcd problems - and you need to make sure you are Ok. Good luck, Rebekah.