How the right dose of selenium can benefit the thyroid

Selenium is an important micronutrient. The amount of selenium in your body depends on the geography of where you live, and where your food comes from (1, 2). Scientists have shown selenium is crucial for maintaining a healthy immune system, hormonal balance, and metabolism.

The thyroid is the organ with the highest concentration of selenium in the body — selenium is used there as a building block of specific proteins called selenoproteins. This is where selenium has immense benefits for the thyroid gland and immune health.

1. Selenium is an antioxidant

Certain selenoproteins are antioxidants — removing free radicals (aka reactive oxygen species) that are generated during the process of building up thyroid hormones in the thyroid gland (3, 4). This is a crucial function in preventing thyroid gland damage and premature ageing.

2. Selenium helps convert T4 into T3

A subgroup of selenoproteins, deiodinases, are essential for converting an inactive T4 into its active form T3 (5).

If your body misses selenium, production of T3 will be lower — causing TSH to rise and forcing the thyroid gland to produce more T4. As a byproduct of that production, there will be more free radicals damaging the thyroid gland, and since selenium is low it won’t be able to function as an antioxidant. This will result in high T4, low T3, and higher than usual TSH. It will also create a scar tissue within the thyroid gland, deeming that part of the thyroid non-functional (6).

3. Selenium can reduce thyroid antibody levels

Research has shown that people taking 200µg of sodium in a form of sodium selenite reduces TPO antibody level by 40% after 90 days (for example, if your TPO was 200 IU/mL, after 90 days it could drop to 120 IU/mL) (7) and 55% after six months (dropping to 90 IU/mL) (8). It’s been shown if you stop taking selenium, your antibody levels will go back up (9).

Which foods contain high selenium?

Meat products, brazil nuts, fish, pasta, rice, bread, cereals, and yeast (10).

What is the best form of selenium supplements ?

Selenium is available as selenomethionine, selenocysteine, selenite, and selenate (1). Selenomethionine and selenocysteine are better absorbed by the gut (11).

Low levels of selenium can still occur even when taking high doses of it — this may be caused by your lifestyle: smoking, continuously eating high quantities of eggs or white rice, drinking alcohol and/or coffee (12).

What’s the right selenium supplement dose?

400 mcg per day is considered too much, and a prolonged exposure to selenium might cause poisoning (13), it will take on average 6 weeks for the excess of selenium to leave your body once you stop taking high doses (14). If you are taking high selenium doses, you might experience skin irritation, lung irritation, diarrhea, hair loss, or nail discoloration.

See how taking selenium daily impacts your thyroid health by tracking your dosage and symptoms in BOOST Thyroid app.


1. Duntas LH, et al. Selenium: an element for life, 2015

2. Rayman MP. Selenium and human health, 2012

3. Schomburg L. Selenium, selenoproteins and the thyroid gland: interactions in health and disease, 2012

4. Saranac L, et al. Why is the thyroid so prone to autoimmune disease, 2011

5. Kohrle J, et al. Selenium, the thyroid, and the endocrine system, 2005

6. Kohrle J. Thyrotropin (TSH) action on thyroid hormone deiodination and secretion: one aspect of thyrotropin regulation of thyroid cell biology, 1990

7. Gartner R, et al. Selenium supplementation in patients with autoimmune thyroiditis decreases thyroid peroxidase antibodies concentrations, 2002

8. Duntas LH, et al. Effects of a six month treatment with selenomethionine in patients with autoimmune thyroiditis, 2003

9. Mao J, et al. Effect of low-dose selenium on thyroid autoimmunity and thyroid function in UK pregnant women with mild-to-moderate iodine deficiency, 2016

10. Waegeneers N, et al. Predicted dietary intake of selenium by the general adult population in Belgium, 2013

11. Thiry C, et al. An in vitro investigation of species-dependent intestinal transport of selenium and the impact of this process on selenium bioavailability, 2013

12. Park K, et al. Demographic and lifestyle factors and selenium levels in men and women in the U.S, 2011

13. Institute of Medicine (US) Panel on Dietary Antioxidants and Related Compounds; N. A. P. (US) Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids, 2000

14. MacFarquhar JK, et al. Acute selenium toxicity associated with a dietary supplement, 2010

Boosted — by BOOST Thyroid App

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Dr. Vedrana Högqvist Tabor

Written by

CEO @Boost_HealthApp|| TEDx speaker || Cancer hunter || Hashimoto’s patient|| Parentpreneur || Learning from own mistakes since 1977

Boosted — by BOOST Thyroid App

Companion health app for people diagnosed with Hashimoto’s and an underactive thyroid.

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