Why is iodine deficiency common in the United States?
We first need to note that the body produces no iodine, and there is no organ other than the thyroid that can store large quantities of iodine. In some areas of the US, including mountain regions, the Mississippi River Valley, the Ohio River Valley, and the Great Lakes regions, the soil has always had a very low iodine content. But even in other areas of once iodine-rich soil, over farming has frequently depleted this iodine content. Hence, we no longer get adequate iodine via the plants we consume. To compensate for this, iodine was added to salt, bread, and milk. Today iodine is no longer added to bread or to milk, and the amount of iodine added to salt has steadily declined over the years. All of these factors contribute to the current prevalence of iodine deficiency in the United States.
