Selenium is an essential trace mineral that occurs naturally in the soil. In the body, selenium is used to produce selenoproteins, which act as antioxidants with vitamin E to protect against cell damage that can lead to heart disease and cancer. Selenium also aids in cell growth and boosts immunity.

In terms of the thyroid, selenium helps convert T4 to T3. A deficiency of selenium might lead to a reduction in available thyroid hormone, causing hypothyroidism. Studies have shown that a deficit of selenium can cause goiters. Some experts believe that too much selenium may also cause thyroid problems, namely hypothyroidism.

Selenium deficiency is rare in the United States, though some studies have suggested that the soil here may not be as rich in selenium as once believed. Some people may have difficulty with absorption if they suffer from severe gastrointestinal illness. But the condition does occur elsewhere in the world, in places such as China, where the soil is not rich in selenium. In regions that also have iodine deficiency, a deficiency of selenium typically makes thyroid disorders even worse.

Sources of Selenium

Animals fed on foods grown in selenium-rich soil are a primary source of selenium in the United States. Selenium is also found in nuts, seeds, and grains that were grown in these types of soil. Selenium is readily available in the diet through numerous foods, including chicken, brown rice, eggs, whole-wheat bread, walnuts, seafood, and liver.

Do I Need a Supplement?

If you have a gastrointestinal disease that inhibits selenium absorption, you probably need selenium supplementation. One example is Crohn's disease, an inflammatory bowel disease that occurs in the small intestine. Selenium supplements have been shown to improve autoimmune thyroiditis. Studies in Germany found that selenium supplements reduced the amount of autoantibodies in the blood. Dr. Friedman recommends that patients on levothyroxine therapy take 200 mcg of selenium a day to aid in conversion of T4 to T3. Selenium supplements are sold in drugstores and health food stores for a reasonable price.