Sea salt naturally has some iodine in it (less than it has Bromine because of both sedimentation and bio absorption). Iodine is in the same column of the periodic table as chlorine, which makes Sodium Iodide (NaI) a natural cohabitor with Sodium Chloride (NaCl) in solution. What's suggested is only 50grams (2oz) per ton or 50ppm... which is less than Bromine in sea water (65ppm). We mammals probably evolved eating a lot more fish!