"While more research needs to be done, it is generally accepted that diet plays a major role in thyroid health. For decades we have known that low iodine intake leads to low thyroid function and eventually to goiter. Iodized salt was intended to solve this problem, but it has not been the answer. There are a number of foods known as goitrogens that block iodine. Two goitrogens are quite prevalent in the American diet---peanuts and peanut butter and soybeans used most often in prepared foods as textured vegetable protein (a refined soy food) and soybean oil.
The rise of industrialization, corporate farming, and mass production of food has drastically changed our food supply from what our ancestors ate. Many studies show the detrimental effects of refined sugars and grains on our health. These foods are very taxing on the thyroid gland, and we consume them in large quantities.
Environmental stress such as chemical pollutants, pesticides, mercury, and flouride are also tough on the thyroid. A growing body of evidence suggests that flouride, which is prevalent in toothpaste and water treatment, may inhibit the functioning of the thyroid gland. Additionally, mercury may diminish thyroid function because it displaces the trace mineral selenium, and selenium is involved in conversion of thyroid hormones T4 to T3." (VIRGIN COCONUT OIL AND THYROID HEALTH)