cold fjord writes "I wish it was always this easy. Business Insider reports, 'Iodized salt is so ubiquitous that we barely notice it. Few people know why it even exists. Iodine deficiency remains the world's leading cause of preventable mental retardation. According to a new study (abstract), its introduction in America in 1924 had an effect so profound that it raised the country's IQ. A new NBER working paper from James Feyrer, Dimitra Politi, and David N. Weil finds that the population in iodine-deficient areas saw IQs rise by a full standard deviation, which is 15 points, after iodized salt was introduced.... The mental impacts were unknown, the program was started to fight goiter, so these effects were an extremely fortunate, unintended side effect.'"