Why is iodine deficiency more common in mountainous regions?

Iodine deficiency is more prevalent in mountainous regions because the soil in these areas typically contains very low levels of iodine.1

Because iodine is an essential nutrient that must be obtained through the diet, the amount of iodine available in food and water directly reflects the concentration of the element present in the local soil. In contrast to coastal areas, where soil is often rich in iodine and iodine-rich seafood is readily available, mountainous regions lack these natural sources. Consequently, populations in these areas are at a higher risk of developing iodine deficiency, which can lead to conditions such as goitre and other thyroid disorders. To mitigate this, many regions address the deficiency by mandating the addition of iodine to table salt.123