If your thyroid is underactive, there is a good chance you have Hashimoto disease. This disorder is the most common cause of an underactive thyroid -- called hypothyroidism -- in the United States, according to the National Institute of Diabetes and Digestive and Kidney Diseases. It is an autoimmune disease in which your immune system attacks the hormone-producing cells in your thyroid gland, causing inflammation and destruction. The mainstay of treatment for Hashimoto disease is thyroid hormone pills. Although no specific diet is recommended for Hashimoto disease, excessive intake of iodine and potentially other foods may affect this condition. Certain medical conditions that can coexist with Hashimoto disease may also require specific dietary modifications.
Iodine is a mineral your thyroid requires to make thyroid hormone. It is added to salt in the United States and many other countries, and it is also found naturally in iodine-rich foods such as kelp and other seaweeds, seafood, dairy products, grains and eggs. Iodine deficiency is the most common cause of hypothyroidism in underdeveloped areas of the world. On the other hand, increased iodine intake may lead to Hashimoto thyroiditis in some people, according to an article in the December 2013 issue of “Hormones.” Although the effects of excessive iodine in people who already have Hashimoto disease have not been established, a normal dietary intake of iodine is probably best, and iodine supplements should only be used if prescribed by your doctor.
Selenium is another mineral necessary for thyroid hormone production, and this nutrient may help protect thyroid cells from damaging free-radical molecules. It is available as supplements and is found in seafood, certain meats, poultry, Brazil nuts, grains, eggs and dairy products. The effects of selenium-rich foods in Hashimoto disease have not been properly studied. A March 2014 “European Thyroid Journal” review of previous studies found that selenium supplements alone or combined with medications decreased thyroid autoantibody levels -- a measure of the anti-thyroid immune reaction -- in people with the disease. However, the authors concluded there is insufficient scientific evidence to recommend the use of selenium supplements, and they stressed that more research is needed to understand how selenium may impact symptoms and treatment of Hashimoto disease.
Cruciferous Vegetables and Soy
When cruciferous vegetables such as cabbage, bok choy, broccoli or brussels sprouts are broken down by the body, a substance is produced that can reduce iodine uptake by the thyroid -- potentially leading to hypothyroidism. A naturally occurring chemical in soy may also reduce thyroid hormone production. For both types of foods, these effects have been primarily noted in animal studies. There have been almost no reports in humans of hypothyroidism caused by eating cruciferous vegetables. Studies of soy consumption in people with normal thyroid function have reported both increased and decreased thyroid hormone production, according to a 2014 article in “Alternative Therapies in Health and Medicine.” Of note, cooking or fermenting these vegetables and soy products reduces or prevents their harmful effects. Maintaining adequate intake of iodine may also limit soy’s negative effects. Cruciferous vegetables and soy contain a wealth of nutrients and provide many health benefits, and in general, moderate consumption may be appropriate. If you have Hashimoto disease, talk to your doctor about these foods.
Diet for Coexisting Diseases
People with Hashimoto disease are more likely than those without the disease to have other autoimmune disorders, including celiac disease, pernicious anemia and type 1 diabetes. Celiac disease requires avoidance of gluten, found in foods and ingredients containing wheat, barley and rye. Pernicious anemia will cause vitamin B12 deficiency. It is treated with supplements and vitamin B12-rich foods such as meat, fish, poultry, eggs and dairy products. Hashimoto disease also increases the likelihood of vitamin D deficiency, which was found in 92 percent of people with Hashimoto disease in a study reported in the August 2011 issue of “Thyroid.” Increasing your sun exposure and consuming vitamin D supplements or vitamin D-rich foods like fatty fish, dairy products, eggs and mushrooms are ways to raise vitamin D to normal levels.
Warnings and Precautions
Additional research is needed to clarify which foods may interfere with thyroid function if you have Hashimoto disease. If you have this condition, consult with your doctor before taking any dietary supplements or prior to making any significant changes to your diet. In collaboration with your doctor, a dietitian can help create a diet plan appropriate for your specific needs. In addition to the potential impact of dietary factors on thyroid function, some foods and supplements may interact with thyroid hormone medication. Soy products, coffee, fiber, calcium and chromium picolinate may all reduce absorption of this medication. Talk with your doctor if you consume these items, as your doctor may recommend increasing your dose of thyroid hormone medication or not consuming these items at the same time as the medication.
Reviewed by: Kay Peck, MPH, RD