What Is Iodine, Exactly?

Iodine is an essential micronutrient — “essential” in that it’s required for your body to function, but your body doesn’t make it, so you can get it only through your diet. Iodine supports virtually every aspect of health, primarily by helping create thyroid hormones. Iodine also has antioxidant, anti-infection, and potential anticancer properties.

A trace mineral, iodine is found in seawater as well as in certain rock formations and soil. Erosion and flooding have depleted soil iodine in many areas of the world, which has led to widespread iodine deficiencies and helps explain why iodine levels in food are so inconsistent (more on this later).

If you look at the periodic table of elements, you’ll see iodine is a halogen, a category that also includes bromine, chlorine, and fluorine. Halogens and halogen-based compounds, called halides, are often used in commercial cleaning products, as well as in pharmaceuticals and food additives. ­Research has found that exposure to some of these halogen-containing compounds can block the absorption of iodine in the thyroid. However, experts disagree about how much everyday exposure may threaten thyroid health — and what to do about it.

“Iodine is unusual in a lot of ways,” says Alan Christianson, NMD, author of The Thyroid Reset Diet. “It’s a high-energy atom. It’s further down on the periodic table than anything else we use nutritionally, so it’s chemically reactive. It has the capacity to trigger a great number of chemical reactions in the body.”