Iodine is an essential element required by humans for the synthesis of thyroid hormones. Therefore, normal functioning of the thyroid gland, a gland actively involved in the regulation of metabolism, requires iodine. Humans obtain iodine from their diets. Iodine deficiency is rare in industrialized countries such as the United States due to the enrichment of table salt with iodine. Under normal conditions, the absorption of dietary iodine is greater than 90 percent 1.
The U.S. Food and Drug Administration (FDA) has established a Reference Daily Intake (RDI) of 150 μg iodine for adults and children 4 or more years of age (21CFR101.9). RDIs are a set of dietary references for essential vitamins and minerals that are considered amounts sufficient to meet the daily requirements of healthy individuals. RDIs serve as the basis for calculating the percent daily value (%DV) amounts found on dietary supplement and food labels.