Selenium

 

Selenium and its Importance for the Thyroid

 

Selenium is a mineral1 naturally found in soil and certain foods2. While our body doesn’t produce it, it plays an important role in our health, especially when it comes to our thyroid. Selenium is found in foods like chicken, eggs, kidneys, liver, tuna, shellfish and Brazil nuts. Our small intestine absorbs it from our food and it’s transported to the liver before being disposed of through the urine and faeces.3

 

Why do we need selenium?

Research has shown that selenium is an antioxidant4 and, while it is believed that too much can be toxic, it plays a major role in maintaining our health, including:5

  • reducing inflammation in autoimmune diseases
  • helping to defend against viral infections
  • increasing blood flow and lowering heart disease risks
  • being a main part of the enzyme that helps the thyroid convert T4 to T36

 

This enzyme is also responsible for getting rid of hydrogen peroxide, a byproduct of thyroid hormone production. When selenium is low, a buildup of hydrogen peroxide may destroy thyroid cells over time.7

Until 2000 researchers believed that selenium deficiency contributed to thyroid conditions only when iodine levels were also low. However, a study published in the Biological Trace Element Research journal of that year presented a case of hypothyroidism caused entirely by lack of selenium.8

Another study9 noted a decrease in selenium levels in patients with autoimmune conditions, which could lead to or worsen inflammation. According to the study, getting enough selenium seems to help manage complications of autoimmune conditions and even improve symptoms, perhaps due to its anti-inflammatory effects.

 

What causes a selenium deficiency?

Being deficient in selenium often comes down to three connecting factors: diet, geographical location and soil composition. In North America, for example, the soil is rich in selenium which means that crops have higher levels of it too. That’s why researchers believe most North Americans get enough selenium through their diet.

In her study, The importance of selenium to human health,10 Margaret Raymond found that the opposite was happening in the UK, where dietary consumption of selenium had dropped by 50% over two decades. This correlated to a reduction in imports of selenium-rich North American wheat in favor of European wheat.

 

What are the symptoms of a deficiency?

Selenium deficiency is known to cause problems for many systems of the body including the cardiovascular system, the immune system and the endocrine system. Many of the symptoms are therefore the same as those of an underactive thyroid:11,12

  • hair loss or changes to hair and nails
  • fatigue
  • brain fog, difficulty concentrating or memory problems
  • muscle weakness and pain
  • weakened immune system, such as susceptibility to colds
  • male infertility

 

Testing for a selenium deficiency

People at risk of a selenium deficiency are those living in regions where soil or crops are selenium-deficient, those undergoing kidney dialysis and people living with HIV.

Testing selenium levels alone can be tricky, especially in the UK where it’s not typically offered. However, you can request a blood test that looks at the amount of selenium in the serum/plasma of the blood.13

You can order private blood tests from the Thyroid UK website – www.thyroiduk.org/tuk/testing/private_tests.html – including selenium and other nutritional markers.

 

Treatment and prognosis

When treating a selenium deficiency the NHS recommends 0.060mg (60 mcg) a day for women (19-64 years) and 0.075mg (75 mcg) a day for men (19-64 years).2 However, healthcare practitioners often treat with higher doses to allow for an optimal level.

Side effects of too much selenium can include hair loss or alopecia, damage to fingernails, nausea, change in bowel movements and problems to the nervous system.12

Experts agree that you should be able to get enough selenium from your diet alone. A single Brazil nut, for example, provides about 80 mcg of selenium.

Research has shown that supplementing selenium can have a positive effect on plasma cholesterol and triglycerides levels.14 However, it’s a good idea to speak with your GP or a nutritionist if you suspect a selenium deficiency before supplementing.

HealthyButSmart.com has a good article “Do Selenium Supplements Have Benefits? 19 Research Papers Examined” if you want to read further about selenium –  https://healthybutsmart.com/selenium-supplements-benefits/

 

Check out what people are saying on our online community regarding selenium:

https://healthunlocked.com/thyroiduk

 

Thyroid UK relies on donations so that we can continue to support and campaign for people with thyroid disease and related disorders.  If you have found our information helpful, please do think about donating or becoming a member.

 

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Glossary

Autoimmune disease – when the immune system mistakenly attacks the body

Brain fog – a general term to describe feelings of confusion or disorientation

Deficiency – a lack of, or shortage of something

Enzyme – a protein that creates a chemical reaction in the body

Hydrogen peroxide – a chemical compound that is used as an oxidising agent (a chemical compound that readily transfers oxygen atoms), a bleaching agent and an antiseptic, small amounts of which are created in the body

Immune system – the organs and processes in the body that work together to resist infections

Plasma – yellowish coloured liquid component of blood

Triglycerides – a type of fat (lipid) found in your blood

 

References

  1. The effect of selenium supplementation on coronary heart disease: A systematic review and meta-analysis of randomized controlled trials
    J Trace Elem Med Biol. 2017 Dec;44:8-16
    Ju WLi XLi ZWu GRFu XFYang XMZhang XQGao XB
    https://www.ncbi.nlm.nih.gov/pubmed/28965605
  2. Vitamins and Minerals
    https://www.nhs.uk/conditions/vitamins-and-minerals/others/
  3. Selenium
    Doley
    Bioactive Food as Dietary Interventions for the Aging Population2013
    https://www.sciencedirect.com/topics/food-science/selenium
  4. Selenium
    John D. Mark MD
    Integrative Medicine (Fourth Edition), 2018
    https://www.sciencedirect.com/topics/medicine-and-dentistry/selenium
  5. Thyroid hormone status in patients with severe selenium deficiency
    Kawai MShoji YOnuma SEtani YIda S
    https://www.ncbi.nlm.nih.gov/pubmed/29662265
  6. Selenium and Thyroid Disease: From Pathophysiology to Treatment
    Mara VenturaMiguel MeloFrancisco Carrilho
    Clin Pediatr Endocrinol. 2018;27(2):67-74
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5307254/
  7. Thyroid Profiles
    ZRT Labs
    https://www.invivoclinical.co.uk/files/thyroid_profiles_pds_05.01.2016.pdf
  8. Selenium deficiency and hypothyroidism
    Antonio Pizzulli,  Alireza Ranjbar
    Biological Trace Element Research
    December 2000, Volume 77, Issue 3, pp 199–208
    https://link.springer.com/article/10.1385/BTER%3A77%3A3%3A199
  9. Selenium and autoimmune diseases: a review article
    Sahebari MRezaieyazdi ZKhodashahi M
    Curr Rheumatol Rev. 2018 Oct 16
    https://www.ncbi.nlm.nih.gov/pubmed/30324883
  10. The Importance of Selenium to Human Health
    Margaret P. Rayman
    https://pdfs.semanticscholar.org/73b1/4abf5792b38e2b98ef2cf74c1541e9f78869.pdf
  11. Selenium Deficiency
    Aparna P. Shreenath; Jennifer Dooley
    https://www.ncbi.nlm.nih.gov/books/NBK482260/
  12. Selenium – Factsheets for Consumers
    National Institutes of Health
    https://ods.od.nih.gov/factsheets/Selenium-Consumer/
  13. Selenium
    https://www.labtestsonline.org.uk/tests/selenium
  14. Effect of Selenium Supplementation on Lipid Profile: A Systematic Review and Meta-Analysis
    Ju WLi XLi ZWu GRFu XFYang XMZhang XQGao XB
    J Trace Elem Med Biol. 2017 Dec;44:8-16
    https://www.ncbi.nlm.nih.gov/pubmed/30312982

 

Date updated: 21/02/20 (V1.1)
Review date: 07/02/21