Why is iodine deficiency less common in many coastal regions?

Iodine deficiency is less common in coastal regions primarily because of the local environment and dietary habits. In these areas, the soil often contains higher concentrations of iodine, which enriches the local food supply. Furthermore, individuals living near the coast are more likely to consume seafood, which is a rich natural source of the element.1

While seawater contains only trace amounts of iodine, certain marine organisms, such as seaweeds, are capable of concentrating it significantly. This natural availability helps ensure that populations in these regions maintain the iodine levels necessary for proper thyroid gland function and the production of essential hormones. In contrast, mountainous areas often lack these sources, making deficiency more prevalent in those inland environments.231