Cruciferous vegetables and hypothyroid: There are certain foods that have tremendous anti-cancer properties and are loaded with healthful nutrients, but contain a compound that can have a subtle effect on thyroid metabolism. They are given the name goitrogens, and include cruciferous vegetables such as broccoli, cauliflower, Brussels sprouts, bok choy, broccolini, Chinese cabbage, kale, kohlrabi, radish, collard greens, and turnips. Many online resources exaggerate the adverse thyroid effects from these foods. People with iodine deficiency or severe hypothyroidism appear to be the only ones affected by very high doses of these raw cruciferous vegetables. But even consuming a serving of these foods daily is not enough to have the said adverse effect. Furthermore, cooking effectively inactivates their goitrogenic activity—a reason to question the fad of “juicing” for general health. In my clinical practice, I have never recommended that anyone avoid these healthful vegetables in their diet. The vegetables should be properly cooked, and you should ensure that you are not overtly deficient in the mineral iodine.
There are goitrogenic compounds in soy products, peanuts, lima beans and millet that do not break down with cooking like the above vegetables. Therefore, if you have thyroid tests that are outside of healthy ranges, these four basic foods are best limited or avoided.[i]
I do talk about his more in my book, The Blood Code: Unlock the secrets of your metabolism.
[i] Masterjohn, Chris. https://www.cholesterol-and-health.com/Goitrogen-Special-Report.html