Necessary nutrient: While it’s a mandatory addition to table salt, many sea salts and kosher salts don’t have iodine added A new study indicates that Americans gained up to 15 IQ points after the addition of iodine to salt became mandatory. In an effort to prevent goiter related to iodine deficiency, authorities ruled that iodine be added to U.S. salt products in 1924. The iodine, in addition...