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What is iodide?

Many people can recall iodine being applied to cuts and scrapes as children. Iodide is like chloride in that it is most comfortable in nature after it has acquired an extra electron and becomes negatively charged (I–).


What foods contain iodide?

The iodide content of foods is mostly related to the soil content in which plants were grown and/or the iodide content of any fertilizers used to cultivate the soil. Furthermore, the iodide content in drinking water usually reflects the iodide content of the rocks and soils through which the water runs or is maintained. Seafood is typically a better source of iodide than freshwater fish. Dairy foods may be a fair source of iodide, but the iodide content of cows’ milk reflects either the iodide content of the cows’ feed and/or the soil content of their grazing region. Iodide deficiency for the most part has been eradicated from many regions of the world including the United States, where iodide is added to salt. Check your salt label for “iodized salt.”

What are current recommendations for iodide intake?

The RDA for iodide is the same for adult men and women at 150 µg daily. However during pregnancy and lactation the RDA increases to 220 µg and 290 µg daily.


What does iodide do in the body?

Iodide is one of the largest atoms found in the body, yet it appears to have only one function. Iodide is a key component of thyroid hormone, which is made in the thyroid gland located in the neck. Thyroid hormone is constructed from iodide and the amino acid tyrosine and has two forms thyroxine (T4) and triiodothyronine (T3) based on the number of iodide atoms (3 or 4). Thyroid hormone affects most cells in the body, perhaps with the exception of the adult brain, testes, spleen, uterus, and the thyroid gland itself. Thyroid hormone promotes the activities associated with glucose breakdown and general energy metabolism and heat production. Today, thyroid hormone is prescribed mostly to treat hypothyroidism, a condition in which the thyroid gland fails to produce adequate thyroid hormone. During the growing years thyroid hormone is very important because it promotes growth and maturation of the skeleton, the central nervous system, and the reproductive organs.


What happens in iodide deficiency?

A deficiency of iodide limits the ability of the thyroid gland to make adequate thyroid hormone. During childhood, an iodide deficiency can result in poor growth, poor maturing of organs, and mental deficits. A striking characteristic of iodide deficiency is an enlargement of the thyroid gland which is commonly referred to as goiter. Treatment of goiter usually begins with iodide-rich foods including iodized salt, which will shrink the goiter with time but not necessarily correct any developmental problems (growth and mental aptitude) in children. Certain foods contain substances called goitrogens that appear to block iodide entry into the thyroid gland. Foods containing goitrogens include broccoli, kale, cauliflower, rutabaga, turnips, Brussels sprouts, and mustard greens. However, we probably do not eat enough of these vegetables to pose a threat. Routine blood tests include T3 and T4 concentrations thus providing a screening tool for thyroid deficiency or other thyroid hormone-impacting diseases.



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