Although thyroid hormone replacement is sometimes needed to get the thyroid gland—the body’s chief metabolism regulator—working properly, other times it falls down on the job because it’s not getting the nutrients it needs. In addition, certain dietary substances can interfere with thyroid function.
Gluten and Thyroid Disease
Gluten, the protein in wheat, barley, and rye, can be problematic for some people with autoimmune thyroid conditions, including Hashimoto’s and Grave’s disease. “[In these disorders,] gluten may cross-react with thyroid tissue, tricking the body into producing antibodies against the thyroid,” Brown-stein says. “I’ve seen many patients spontaneously resolve an autoimmune thyroid illness just by coming off gluten.” Consult your doctor before starting a gluten-free diet.
Iodine is key. Your body uses iodine to make thyroid hormones. Iodine is found in fish, seaweed, dairy products, and iodized salt. “Although many Americans assume they get enough iodine by consuming iodized salt, processed food is the largest source of dietary salt, which is typically non-iodized, so iodine short-falls are common,” says David Brownstein, MD, author of Iodine: Why You Need It, Why You Can’t Live Without It.
Supporting nutrients. The amino acid tyrosine, which the body can make from other proteins, (although it’s also found in foods such as chicken, turkey, lima beans, and almonds) combines with iodine to make thyroid hormones. The antioxidant selenium, found in Brazil nuts, seafood, and whole grains, helps protect the thyroid gland from damage during thyroid hormone production and helps convert thyroid hormones to the ac-tive form, Brownstein says. Several other nutrients support thyroid hormone synthesis and function, notably iron and zinc, found in lean meats, poultry, and legumes; vitamins A and B12, found in milk and eggs; and magne-sium, found in nuts and seeds.
Antagonistic dietary factors. Some foods contain goitrogens, substances that can interfere with thyroid hormone production and may contribute to development of a goiter, or swelling of the thyroid gland, says Susan Allen, RD, of Palm Harbor, Florida. “Soy contains goitrogens, as do raw cruciferous vegetables, such as broccoli and cabbage,” Allen says. However, cooking often inactivates goitrogens, which are typically only problematic if you’re deficient in iodine.
Another antagonist is bromine, which competes with iodine for absorption. Although bromine-based addi-tives are used less commonly now due to carcinogenic concerns, you still can find them in commercial bakery and restaurant products made with bromated flour, certain citrus-flavored sodas, some prescription drugs, and as an environmental contaminant, Brownstein says. Bromine labeling requirements for restaurant and bakery foods vary according to state and local laws.
—Marsha McCulloch, MS, RD