Foods That Decrease Thyroid Function

Raw Cruciferous Vegetables

Cruciferous vegetables, although highly nutritious, release a compound called goitrin during digestion. Goitrin can interfere with thyroid function, says Cheryl Harris, a registered dietitian and contributing writer for "Today's Dietitian." The effects can be severe if you also have an iodine deficiency, which affects some people with hypothyroidism. Cooking cruciferous vegetables, such as broccoli, cauliflower, kale and brussels sprouts, takes away most or all of their goitrogenic properties.

Soy

Soy can also be goitrogenic, and substances within soy called isoflavones can reduce thyroid hormone production. Sheila Dean, a registered dietitian at the Palm Harbor Center for Health and Healing in Florida, recommends that people with thyroid conditions consume soy in moderation. This means limiting your consumption of tofu, edamame, soy nuts and soy-based meat and dairy product alternatives to roughly one or fewer servings per day. One serving of soy is equal to 1 cup of soy milk, 1/2 cup of soybeans or 2 to 3 ounces of tofu.

High-Fiber Foods

High-fiber foods are a vital part of most healthy diets. A fiber-rich diet can help minimize thyroid-related symptoms, such as excessive food cravings and constipation. Eating high-fiber foods with synthetic thyroid medications, however, can reduce the drugs' absorption, says Dr. Todd B. Nippoldt, a Mayo Clinic endocrinologist, leading to reduced thyroid function. To avoid these risks, take thyroid medications with low-fiber foods, such as eggs or salad, or between meals on an empty stomach. Particularly fiber-rich foods include beans, lentils, raspberries, whole grains and artichokes.

Gluten and Millet

Gluten is a protein found in wheat, barley and rye that causes intestinal damage in people with celiac disease. A strong link exists between autoimmune thyroid disease and celiac disease, says Harris. Avoiding gluten may improve thyroid function even if you have hypothyroidism without celiac disease. Common sources of gluten include white and wheat breads, cereals, pastas, crackers and wheat-based snack foods. Gluten-free whole grains, which provide B-vitamins -- nutrients that may reduce hypothyroidism symptoms -- include brown rice, wild rice, quinoa, gluten-free oats and popcorn. While millet is a gluten-free whole grain, it has goitrogenic properties. Excessive intake may reduce thyroid function.