Iodine in biology
The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for iodine in 2000. For people age 14 and up, the iodine RDA is 150 μg/day; the RDA for pregnant women is 220 μg/day and the RDA during lactation is 290 μg/day. For children 1–8 years, the RDA is 90 μg/day; for children 8–13 years, 130 μg/day. As a safety consideration, the IOM sets tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. The UL for iodine for adults is 1,100 μg/day. This UL was assessed by analyzing the effect of supplementation on thyroid-stimulating hormone. Collectively, the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).
Iodine-131
A common treatment method for preventing iodine-131 exposure is by saturating the thyroid with regular, non-radioactive iodine-127, as an iodide or iodate salt. Free elemental iodine should not be used for saturating the thyroid because it is a corrosive oxidant and therefore is toxic to ingest in the necessary quantities. The thyroid will absorb very little of the radioactive iodine-131 after it is saturated with non-radioactive iodide, thereby avoiding the damage caused by radiation from radioiodine. The most common method of treatment is to give potassium iodide to those at risk. The dosage for adults is 130 mg potassium iodide per day, given in one dose, or divided into portions of 65 mg twice a day. This is equivalent to 100 mg of iodine, and is about 700 times bigger than the nutritional dose of iodine, which is 0.150 mg per day (150 micrograms per day). See potassium iodide for more information on prevention of radioiodine absorption by the thyroid during nuclear accident, or for nuclear medical reasons. The FDA-approved dosing of potassium iodide for this purpose are as follows: infants less than 1 month old, 16 mg; children 1 month to 3 years, 32 mg; children 3 years to 18 years, 65 mg; adults 130 mg. However, some sources recommend alternative dosing regimens.