Why is iodine added to table salt?

Iodine is added to table salt primarily to prevent iodine deficiency, a condition that occurs when the body does not receive enough of this essential element through diet.12

Iodine is critical for the production of thyroid hormones, which regulate metabolism, heart function, nerve response, and body growth. When dietary intake is insufficient, the thyroid gland may enlarge, leading to goitre. In severe cases, deficiency can cause hypothyroidism, intellectual disabilities in infants, and cretinism.13

Because iodine is naturally scarce in the soil and water of many regions, populations living in these areas are at higher risk of deficiency. To address this public health concern, government officials in many countries have made the addition of iodine—typically in the form of potassium iodide—to table salt mandatory. This simple, effective measure has been instrumental in reducing the prevalence of iodine-related thyroid diseases worldwide.123