Actually, what happens is the organs which require Iodine undergo a process called "organification," where enzymes make Iodine from iodide. The breast tissue is one of these organs which do this. Iodine does not occur anywhere in nature in any food source. All ingestible forms of iodine are in the Iodide form. The enzyme which accomplishes this organification in the thyroid gland is called thyroid peroxidase and the one in breast tissue is lactoperoxidase.