Iodine is a halogen element that exists as a shiny purple-black solid at room temperature. It is an essential nutrient because it is a key component of thyroid hormones, which regulate metabolism, body temperature, and other important functions. Humans can obtain iodine from food sources like seafood and dairy products, as well as iodized salt. About 1/3 of the world’s population is at risk of iodine deficiency, which can cause stunted growth, goiter, intellectual disability, and other health problems. However, excessive iodine intake can also be harmful, so it is important to get the right amount.