While the medical community disagrees about the value of many nutritional supplements, some added nutrients have made an undeniable impact on public health — including one that has the power to raise IQs. Iodine is a critical micronutrient that humans require for good health, successful reproduction and healthy brain development.

Iodine deficiency leads to problems with the thyroid, including cancer, hypothyroidism and goiter. Goiter is a condition in which the thyroid swells up and is visible in the neck, causing swallowing and respiratory problems. In children, iodine deficiency is a leading cause of stunted body growth and intellectual deficiencies, including mental handicaps. The problem isn’t just limited to the developing world; Europe has one-fifth of the world’s iodine deficiency cases.