You may have heard warnings that thyroid patients shouldn’t eat cruciferous vegetables such as broccoli, cabbage, kale, and spinach. At the same time, these vegetables are often called “superfoods” because they’re rich in vitamins and minerals and offer many health benefits. Making smart, thyroid-friendly decisions about what you eat requires an understanding of goitrogenic foods and their effect on your thyroid.
What are goitrogens?
Goitrogens are a category of foods that contain a natural chemical, goitrin, which interferes with your thyroid function.
Under normal circumstances, your body uses the iodine you ingest in food and supplements in order to manufacture your two primary thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Goitrin has the ability to block your body’s use of iodine, which decreases your hormone production and can cause hypothyroidism. Goitrin can also enlarge your thyroid, a condition known as goiter.
The key goitrogenic foods are cruciferous vegetables. Among the most potent goitrogenic foods are:
- Bok choy
- Brussels sprouts
- Russian kale
Some of the least potent goitrogenic foods include the following:
- African cassava
- Babassu, a coconut fruit native to Africa and Brazil
- Chinese Broccoli
- Commercial Kale
- Mustard Greens
- Pine nuts
- Red Radish
Soy is also a goitrogen, but it belongs in its own category because in addition to its goitrogenic potential, soy also has chemical properties that can block the body’s ability to properly absorb thyroid hormone.
The goitrogenic potential of foods is greatest when the foods are eaten raw, when you are deficient in iodine, and when you are deficient in selenium. The impact of goitrogenic foods is also “dose-dependent,” meaning that your risk increases the more frequently you consume these foods. Steaming or cooking, however, can eliminate much of their goitrogenic properties.
For those of you who don’t have a thyroid condition, it is considered safe to include some goitrogenic foods in your diet, whether raw or cooked. There is some risk of an impact on your thyroid, however, if you overconsume raw juices that include goitrogenic vegetables. Many juicing recipes call for as much as 3 to 4 cups of cruciferous vegetables (such as spinach or kale) to get just one glass of juice. Since juicing requires large quantities of these vegetables, raw juices can deliver large and concentrated amounts of thyroid-slowing goitrin.
Goitrogen guidelines for thyroid patients
If you are being treated for a thyroid condition, there are some considerations you will want to keep in mind regarding goitrogenic foods.
After radioactive iodine (RAI) ablation: If you’ve had RAI to treat Graves’ disease/hyperthyroidism, most experts consider it safe for you to eat goitrogens, whether raw or cooked.
After thyroid surgery: If you’ve had surgery to remove your thyroid as a treatment for thyroid cancer, goiter, nodules, or hyperthyroidism, most experts consider it safe for you to eat goitrogens, whether raw or cooked.
Graves’ disease/hyperthyroid: If you have Graves’ disease and/or are hyperthyroid, some holistic and naturopathic physicians suggest that you increase the amount of raw goitrogenic foods in your diet as a natural way to slow down your production of thyroid hormone. If you are taking antithyroid drugs, you may also find that you can reduce the dosage of your medication.
Hypothyroid with a thyroid gland: If you are hypothyroid and still have a thyroid gland that is at least partially functional, you may want to be more careful about goitrogenic foods. Some tips:
- Avoid overconsumption of goitrogenic foods in general.
- If you do want to include these foods in your diet, remember that proper preparation — cooking, steaming, or fermenting — can reduce their goitrogenic properties.
- Be careful about drinking raw juice that uses cruciferous vegetables and concentrates their goitrogenic properties.
- Since iodine and selenium deficiency increase the impact on goitrogens on your thyroid, ask your practitioner to run tests for iodine and selenium deficiency, and supplement them if you are deficient.
- Keep in mind that even when you reduce the goitrogenic potential through cooking, soy foods contain chemicals that have the ability to block absorption of thyroid hormone. Avoid overconsumption of soy foods, especially super-concentrated forms of soy, such as soy supplements.
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Mary Shomon is a thyroid disease, hormonal and autoimmune health writer, and patient advocate. For two decades, Mary has been a leading force advocating for more effective, patient-centered thyroid and hormonal health care. Mary is the New York Times bestselling author of “The Thyroid Diet Revolution,” “Your Healthy Pregnancy with Thyroid Disease,” “Living Well With Hypothyroidism,” and 10 other books on thyroid disease and integrative health. She co-stars in two PBS health specials, “Healthy Hormones,” and “Vibrant for Life.” Follow her on Twitter at @thyroidmary or at her Facebook communities: ThyroidSupport and ThyroidDiet.