Selenium and iodine, along with iron and zinc, are trace elements essential for normal thyroid function. The thyroid gland is about 2 inches long, sits at the front of your neck and helps to regulate your metabolism. For men and women age 14 and older, the recommended dietary allowance–the amount you should get each day–for selenium and iodine is 55mcg and 150mcg, respectively. Consult your physician before altering the amount of selenium and iodine in your diet to address a dysfunctional thyroid.
Selenium in the Thyroid
The thyroid needs selenium to function normally. Selenium plays a part in helping your thyroid produce the proper amount of hormones and helps protect the gland against iodine exposure. A normal thyroid gland contains a high selenium concentration even when you ingest an inadequate supply.
Iodine in the Thyroid
Without an adequate amount of iodine, your thyroid gland cannot produce the hormones required for your body to function normally. An iodine deficiency causes hypothyroidism, an underactive thyroid gland. When you have hypothyroidism your thyroid gland becomes enlarged and may develop into a goiter. Women, pregnant women and older children have a higher risk of developing hypothyroidism. However, cases of iodine deficiency are rare in the United States.
Supplements
Selenium and iodine supplementation offers little benefit to people with hypothyroidism caused by an iodine deficiency, according to a study from the University of Otago in New Zealand and reported in the October 2009 issue of the “American Journal of Clinical Nutrition.” In the study, 100 people between the ages of 60 and 80 took either selenium and iodine supplements or placebo. The selenium supplement did not improve the amount of hormones produced by the thyroid. The iodine supplement improved the participant’s iodine deficiency. Researchers found the two minerals did not work synergistically to produce thyroid benefits.
Breast Cancer
As of date of publication, there is suggestive evidence that selenium and iodine work together to prevent breast cancer by keeping your thyroid gland healthy, according to a hypothesis based on data about the diet of Japanese women from Royal Jubilee Hospital in Canada and reported in the February 2000 issue of the journal “Cancer Causes and Control.” Researchers were trying to associate a dysfunctional thyroid with higher breast cancer rates and figure out why Japanese women have a lower rate of “benign and malignant breast disease” than women eating Western diets. They hypothesized the high selenium and iodine content of seaweed keeps the thyroid healthy, thus reducing the rates of breast cancer. Seaweed is a common ingredient in Japanese cooking, but is not popular in Western recipes.
References
- "Thyroid"; The Impact of Iron and Selenium Deficiencies On Iodine and Thyroid Metabolism: Biochemistry and Relevance to Public Health; M.B. Zimmermann, et al.; October 2002
- "American Journal of Clinical Nutrition"; Selenium and Iodine Supplementation: Effect On Thyroid Function of Older New Zealanders; Christine D. Thomson, et al.; October 2009
- “Cancer Causes and Control"; Hypothesis: Iodine, Selenium and the Development of Breast Cancer; S. A. Cann, et al.; February 2000
- MedlinePlus: Iodine in diet
- MedlinePlus: Selenium in diet
