Most doctors tell you to eat more broccoli because it's good for you, unless you have hypothyroidism, a medical condition characterized by low levels of thyroid hormones. Goitrogens are substances found in foods such as broccoli that interfere with the production of thyroid hormones. Your doctor may recommend an anti-goitrogenic diet as one way of dealing with low thyroid hormone levels.
Hypothyroidism is the most common thyroid condition in the United States. The thyroid is a gland responsible for regulating the metabolism of fat and carbohydrates, and low thyroid hormone levels affect metabolism, which can lead to weight gain. Many people with hypothyroidism have a difficult time losing weight until hormone levels are stabilized. Following a diet that limits foods affecting hormone levels, such as goitrogens, may be an important mode of treatment.
Watch Those Cruciferous Vegetables
In addition to broccoli, cruciferous vegetables include Brussels sprouts, cabbage, cauliflower, collard greens, Chinese cabbage and kale. While cruciferous vegetables are a source of goitrogens, they only seem to have an effect on thyroid hormones when iodine levels are low, notes Cheryl Harris, dietitian and health coach in Virginia. Cooking these vegetables denatures the goitrogens, which may make them safe to eat. For thyroid hormone balance, do not eat more than 5 ounces of raw cruciferous vegetables a day.
Goitrogens in Soy
Soy foods are also a source of goitrogens. Like, cruciferous vegetables, the goitrogens in soy seem to have an effect on thyroid hormone production only when iodine levels are low in people with hypothyroidism. However, Shiela Dean, dietitian at the Palm Harbor Center for Health and Healing in Florida, suggests people with hypothyroidism limit their intake of soy foods. Your doctor can help you determine how much soy is safe for you to eat. The Cleveland Clinic says if you're borderline hypothyroid, which means your thyroid produces some hormones, you should not eat soy every day. Non-fermented soy foods, such as soy milk, tofu and soybean oil, contain goitrogens; however, fermented soy foods, such as tempeh and soy sauce, are safe to eat because the fermentation process denatures the goitrogens.
Millet, a gluten-free whole grain eaten as a side dish or cereal often used to make the Indian flatbread roti, is also a source of goitrogens. But unlike cruciferous vegetables and soy foods, adequate iodine levels do not protect you against the goitrogenic effects of millet on thyroid production. Consider eating grains other than millet if you have hypothyroidism.