IODINE

Facts

• Iodine is converted to iodide in the gut, absorbed in the digestive tract and then carried into circulation. Most iodide is trapped by the thyroid gland where it then forms an essential component of thyroid hormones.1
• Estimates are that the body contains 25 mg of iodine.2

Functions

• Required in only trace amounts, iodine helps metabolise excess fat and is key for physical and mental development.
• Iodine is important for proper functioning of the thyroid gland and for the prevention of goiter, an enlargement of the thyroid gland. 1-3
• The condition of the hair, skin, nails and teeth are all dependent on the proper functioning of the thyroid as is the conversion of carotene to vitamin A.2

Requirements

The Recommended Dietary Allowance for iodine is: 150 µg

Signs of Deficiency

In adults an iodine deficiency can result in hypothyroidism, a reduced rate of thyroid hormone secretion characterised by lethargy, weight gain and sometimes goiter. A deficiency can result in impaired growth and neurological development and has been linked with thyroid cancer in a number of studies.4 In adult women, iodine deficiency has been linked with breast cancer.3,5 In children, a iodine deficiency can result in mental retardation, growth stunting, impaired movement, speech or hearing and cretinism.

Interactions

Certain foods, consumed raw and/or in large quantities can inhibit the uptake of iodine by the thyroid gland. These foods include: Brussels sprouts, cabbage, cauliflower, kale, peaches, pears, spinach and turnips.3

Signs of Toxicity

Large doses of iodine can produce a metallic taste in the mouth and sores in the mouth, swollen salivary glands, diarrhoea and vomiting.3,5

Current Research

Brain function
Researchers have linked low iodine consumption with impaired cognition. Countries such as China, Ecuador, Indonesia, Switzerland and Zaire, for example, traditionally have a low rate of iodine excretion in the urine.1 In Indonesia, supplementing infants with iodised oil reduced infant mortality less than 4 months of age.1

Immune Function
According to Alexander Schauss, "Iodine also plays an important role in the immune system where it supports the microbicidal activity of polymorphonuclear leukocytes."6

1 Mercer L.P., West, K. Iodine. http://www.nutrition.org/nutinfo/content/iodi.shtml