Iodine was one of the first minerals recognized as essential to human health. For centuries, it has been know to prevent and goiter-enlargement of the thyroid gland. As part of several thyroid hormones-Iodine strongly influences nutrient metabolism, nerve and muscle function, skin, hair, tooth, and nail condition, and physical and mental development. Iodine may also help convert beta-carotene into vitamin A, and it is an effective antiseptic and water sterilizer.

Iodine deficiency is now uncommon, beside goiter, the effects of deficiency include weight gain, hair loss, listlessness, insomnia, and some forms of mental retardation.