How Can Selenium Help the Thyroid?

Selenium is a micronutrient that generally has a positive effect on our immunity. Many studies have proven Selenium to be beneficial to most immune responses in our body. Like the armed forces that branches into the army, the navy and air force, our bodies have different groups of defence mechanisms which have similar goals but differing methods or tools for defence. Most of these studies show that there is an improvement in immunity when a person has Selenium deficiency, however the results are less clear regarding the benefits of Selenium supplementation in a subject with normal Selenium levels. In cases of asthma and allergies, Selenium deficiency seems to reduce flare-ups.
How does selenium work on the thyroid?
Selenium is essential for the conversion of T4 to T3. T3 is the active form of thyroid hormone. Having low levels of T3 can lead to hypothyroid symptoms, such as constipation, lethargy and weight gain. If this is true, perhaps high levels of Selenium might lead to hyperthyroidism causing palpitation, sweating, tremors and diarrhea although this is unclear. There has also been reports that Selenium reduces inflammation of the thyroid caused by autoimmune disease, by reducing thyroid peroxidase antibody which are responsible for mounting up an immune response against the thyroid. Adequate level of Selenium supports efficient thyroid hormone synthesis and metabolism and prevents it from damage from excessive iodine level.
Should everyone take Selenium supplements then?
Preliminary studies have shown benefit in autoimmune thyroid disease, cancer prevention, viral and non-viral infections in those with initial Selenium deficiency taking supplements. However, we do not yet understand how high levels of Selenium would affect our bodies. Since stronger evidence of benefit has been demonstrated in those with Selenium deficiency, those with normal levels should avoid taking supplements until more studies have been conducted. In the meantime, one can include Selenium-rich foods in their diet. Great sources include brazil nuts, cod, shrimp, tuna, salmon, chicken and eggs. It would be best to consult professional opinion before commencing Selenium supplements.
References:
- http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3723386/
- http://www.ncbi.nlm.nih.gov/pubmed/12487769
- http://chriskresser.com/important-update-on-selenium-supplementation/
- http://ajcn.nutrition.org/content/87/2/379.short