In addition to promoting goiter formation, goitrogenic foods can act like antithyroid drugs, slowing down the thyroid, and ultimately causing hypothyroidism, an underactive thyroid.
Goitrogens are able to disrupt normal thyroid function by inhibiting the body’s ability to use iodine, block the process by which iodine becomes the thyroid hormones thyroxine (T4) and triiodothyronine (T3), inhibit the actual secretion of thyroid hormone, and disrupt the peripheral conversion of T4 to T3.
The key goitrogen-rich foods are the vegetables in the cruciferous category. In addition, there are a number of other foods that contain significant amounts of goitrogens.
Some of the more common and potent goitrogens include the following vegetables, fruits and other foods:
- African cassava
- Babassu (a palm-tree coconut fruit found in Brazil and Africa)
- Bok choy
- Brussels sprouts
- Chinese Broccoli
- Pine nuts
- Red Radish
If you are hyperthyroid, a diet rich in goitrogens may help slow down the thyroid somewhat. (But note that any natural approaches to managing hyperthyroidism and Graves' disease should always be overseen by a physician.)
If you are hypothyroid due to thyroid surgery known as thyroidectomy -- for example, you're a thyroid cancer survivor, or you've had your thyroid surgically removed due to a goiter or nodules -- you don’t need to be particularly concerned about goitrogens.
If you still have a thyroid, however, you should be careful not to overconsume large quantities of goitrogenic foods. This does not mean you need to avoid your favorite foods however. The enzymes involved in the formation of goitrogenic materials in plants can be at least partially destroyed by heat, allowing you to enjoy these foods steamed or cooked.
If you are a heavy consumer of cooked goitrogens, however, and have a difficult time balancing your thyroid treatment, you may consider cutting back on the amount of goitrogenic foods in your diet. Note that soy falls into the general category of goitrogens, but beyond the goitrogenic properties, it has other abilities as a phytoestrogen to affect thyroid function, whether you have a thyroid gland or not.