Your thyroid is essential for healthy metabolism. If it isn't functioning properly, you may lack energy, experience unexplained changes in weight or have difficulty concentrating. Two types of foods may affect your thyroid -- those containing iodine and those containing substances called goitrogens. Your thyroid needs iodine to produce the many types of thyroid hormones, while goitrogens inhibit thyroid function.
Iodine deficiency is rare in America, according to Medline Plus. Iodized table salt is the main source of iodine in the American diet, so limiting salt decreases iodine consumption. Just one teaspoon contains 95 micrograms of the 150 you need each day, however, so even on a low-salt diet you're likely to get enough iodine. Seaweed provides as much as 1,989 percent of the daily value per gram, making it the best iodine source. Other foods that provide at least 10 percent of the daily value of iodine per serving include seafood, milk, yogurt, chocolate ice cream, eggs and enriched grain-based foods like macaroni and bread.
Goitrogenic foods include cruciferous vegetables, such as broccoli, cabbage, Brussels sprouts, radishes, mustard greens and cauliflower. Rapeseed and canola, used to make oils, also contain goitrogens, as do peanuts, soybeans, cassava, spinach, kale, sweet potatoes, strawberries, pears and peaches. Goitrogenic foods can interfere with thyroid function; however, these foods only significantly affect thyroid function if your iodine intake is low. Cooking foods inactivates goitrogens and stops them from affecting your thyroid function, according to an article published in "Toxins" in September 2010.