Yet iodine deficiency remains the world’s leading cause of preventable mental retardation. Prenatal iodine deficiency as well as deficiency in adulthood leads to compromised intelligence as measured by IQ testing, especially in the developing nations that report some of the world’s lowest IQ scores. In 2007, Kul Gautam, the deputy executive director of UNICEF, announced, “Today over one billion people in the world suffer from iodine deficiency, and 38 million babies born every year are not protected from brain damage due to IDD.”7

Iodized salt. Because iodine deficiency remains the greatest global cause of mental retardation, buy only iodized salt, and avoid sea salt unless it is infused with iodine, because processing removes its natural iodine. If you adopt a low-salt diet for health reasons, ask your doctor to recommend alternative sources of iodine. Some European salt and Himalayan salt contains fluoride, additional amounts of which should be avoided by pregnant women and very small children. Water in the United States is already fluoridated, and more than fifty studies suggest that additional fluoride may cause an IQ drop in the very young.