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Why do we need iodine and how much? (It doesn't even taste good and is used in antiseptics!)

Iodine (iodide is the negatively-charged form and both terms are used interchangeably) is an essential mineral nutrient found in our diet. It is a key structural component of thyroid hormones. In the western world, iodine is derived from iodized salt, iodate preservatives in baked goods, dairy products, food coloring, and seafood.

However, dietary iodine deficiency affects an estimated 100 million people in the world; especially in mountainous and inland regions where over millennia, iodine has been leached from the soil. The World Health Organization recommends a daily dietary iodine intake of 150 g for adults, 200 g for pregnant and lactating women, and 50 to 120 g for children.

When iodide intake is less than 50 g per day, the thyroid cannot sustain adequate hormone production, with resulting gland enlargement (goiter) and, ultimately, hypothyroidism.

The consequences of endemic dietary iodine deficiency are especially devastating for the developing fetus and children, who require thyroid hormone for normal neurologic development and growth. Infants afflicted with iodine deficiency appear normal at birth, but will later developed characteristic signs and symptoms; which include jaundice, feeding problems, hypotonia ('floppy baby'), enlarged tongue, delayed bone maturation, and if treatment is delayed, permanent neurologic damage will result. This cluster of symptoms is classically described as cretinism.

Other congenital malformations, especially cardiac, are four times more common in congenital hypothyroidism.

Thyroid hormone essentially comprises of a protein and an iodide moiety.
The follicular cells of the thyroid gland are specialized in their ability to synthesize the large hormonal precursor protein thyroglobulin, concentrate iodide from the circulation and bind the iodide to the thyroglobulin, producing thyroid hormones; which are potent biochemicals that (as mentioned) regulate various processes of metabolism, growth and development.

Incidentally, the thyroid gland is the ONLY organ in our body that utilizes iodine. Any surplus is filtered out by the kidneys. It is interesting to note that the thyroid gland concentrates and uses only a fraction of the iodide supplied to it for hormone synthesis, and the remainder returns to the extracellular fluid pool. Thus, this extracellular pool provides a 'safety' buffer in the event of temporary dietary iodine deficiency. Thus, there is no need to use thyroid as diet supplementation if you are not living deep in the Andes or inland China.

Learn more about this author, Ernie Yap.
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