Role of Iodine as an Antioxidant in Evolution

www.onk.ns.ac.rs/Archive Vol 21, No. 2, June 2013 INTRODUCTION Iodine is the required element in the diet richest in electrons. Inorganic iodides are necessary for all living vegetable and animal cells, but only the Vertebrates have the thyroid gland and its iodinated hormones. In humans, the total amount of iodine is about 15-50 mg and roughly 80 % is located in the thyroid gland (1, 2). The US Food and Nutrition Board of the Institute of Medicine has estimated a daily iodine requirement for adults of 150 μg/day and a tolerable upper intake level of 1100 μg/day (2). The upper intake level is defined as the highest level of daily iodine intake that is likely to pose no risk of adverse health effects in almost all individuals. However, intake levels considerably above the upper intake level are well tolerated by most individuals (2). Although iodine is one of essential microelements, one third of the world’s population lived in iodine-deficient areas (3). Iodine deficiency induces: 1) goiter, including toxic nodular goiter, increased occurrence of hypothyroidism in moderate-to-severe iodine deficiency; decreased occurrence of hypothyroidism in mild iodine deficiency, increased susceptibility of the thyroid gland to nuclear radiation at all ages; 2) abortion, stillbirth, congenital anomalies, perinatal mortality in fetus; 3) infant mortality, endemic cretinism, child and adolescent; 4) impaired mental function, iodineinduced hyperthyroidism in adults (3). At present time the primary intervention for preventing iodine deficiency disorders worldwide is through the iodization of salt (4). The two most common types of fortificant used to iodize salt are potassium iodide (KI) and potassium iodate (KIO3). In general, potassium iodate (KIO3) is preferred because of its stability (4). Since one-third of the world’s population lived in iodine-deficient areas (3), and they use iodine compounds supplementation in food, it is warranted to assess possible toxic effects of these compounds. The last review paper concerning toxicology of these compounds was published in 2001 (5). The aim of this mini-review was to assess possible toxic effects of iodine and iodine-containing compounds with special emphasis on genotoxicity and carcinogenicity studies.