Water retention in legs could be due to either hormonal imbalance or due to poor blood circulation in the extremities (legs and feet). You need not avoid salt completely but limit its intake to not more than 2-3 gm a day. You can sprinkle some salt on cooked food (cooked without addition of salt). Avoid salted and salt preserved foods/packaged foods which contain alot of sodium. Read food labels for sodium content. You must try to stay physically active throughout the day. Physical activity helps in redistribution of fluids accumulated in one area of the body. You might get iodine deficiency if you do not consume any other food sources of iodine like seafood, lotus stem etc.