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Selenium: a mineral for the immune and nervous systems


Selenium is a versatile mineral that is essential for our immune system and thyroid gland. The mineral selenium is essential for our immune system and our thyroid gland. A deficiency, as well as a surplus, are harmful to our health. Just one Brazil nut a day can provide you with the necessary amount of selenium.

The element selenium was discovered in 1817 and named after the Greek moon goddess Selene. 200 years later, researchers have still not fully explored the potential of the trace element. Selenium works almost everywhere in the body - in our immune system, nervous system, muscles and thyroid gland. A deficiency is hard for the body both physically and psychologically. But too much selenium is also unhealthy and can even be life-threatening.  

In this article, you will learn which foods you should consume to cover your daily selenium requirements and which symptoms indicate a deficiency or excess. Also: Why selenium preparations may be harmful to your health.

What is selenium?

Selenium is an essential trace element, which means: It can only be absorbed through food and you only need a small amount of it. The human body stores 13 to 30 milligrams of selenium. The majority of it is deposited in the muscles and thyroid gland.[1]

Good to know: When selenium-containing metal is burnt, a radish-like smell is created[2].

How does selenium work?

Selenium forms important proteins, which strengthen the immune system and prevent cell damage. It reinforces the function of Vitamin E and Vitamin C as defence vitamins. Together with iodine, selenium produces thyroid hormones which boost sperm production and maintain the function of the nervous system. Without selenium, the liver and pancreas would not be able to perform their digestive and blood sugar functions.[3, 4]

Selenium and heavy metals: Selenium can help in the body to bind the heavy metal lead. A heavy metal in bound form can no longer harm the body and can be excreted more easily.[5]

What is the daily selenium requirement?

According to the recommendations of the German Nutrition Society, an adult man should consume 70 micrograms of selenium per day. For women, the requirement is 60 micrograms. Breastfeeding women have an increased need of 75 micrograms to provide their child with sufficient selenium via breast milk[6].

Which foods contain selenium?

Are Brazil nuts radioactive?

Both animal and plant foods provide selenium to the body. The amount of selenium contained in plant foods also depends on where they were cultivated and how selenium-rich the soil was. No food contains as much selenium as coconut and paranut. Only one Brazil nut can cover your daily requirement [7].

Other selenium-rich foods are[8]:


Micrograms per 100 grams

Tuna fish


Wheat bran

60 to 130



Brussels sprouts


White beans


Swiss Cheese



Selenium deficiency

The soil in Europe has lost a lot of selenium over the years. Climate change is supposed to be to blame for this, as it promotes extreme weather conditions. The result: Heavy rainfall washes the selenium out of the soil, and prolonged dry periods also reduce the selenium content. If there is too little selenium in the soil, it cannot accumulate sufficiently in plants, making food less selenium-rich.[9, 10]. The last study on how much selenium people consume in Germany was conducted in 1996. The Germans absorb an average of 40 micrograms selenium per day - less than professional societies recommend[11].

That's good to know: The soil with the highest selenium content is located in Nebraska in the USA. The soil in China, on the other hand, has a low selenium content.[1].

Selenium deficiency - Risk groups

Apart from people who eat a diet low in selenium, a deficiency can occur in the following groups[12, 13]:

  • Smokers
  • Alcoholics
  • Women who breastfeed of an extended amount of time
  • People suffering from intestinal diseases - selenium cannot enter the bloodstream
  • Dialysis patients - a lot of selenium is lost during blood purification

The 6 best sources for selenium

What are the symptoms of selenium deficiency?

Because selenium works almost everywhere in the body, a deficiency can lead to a number of symptoms[11, 14]:


General complaints

Muscle weakness and joint pain
Impaired sperm production

Psychiatric complaints

Depressive moods and mood swings

Organic complaints

Diseases of the thyroid gland and heart muscle
Liver disorders


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Selenium supplements

270 out of 1073 people, i.e. about one in four, stated in a survey on dietary supplements that they were taking selenium preparations. The right supplements can help you optimize your selenium intake - but there are a few things to consider[15].

Which selenium tablets are best?

A good selenium preparation should contain selenomethionine. The body can absorb 90 per cent of this selenium compound. Other selenium compounds such as sodium selenite or sodium selenate can only be absorbed in part.[1].

How much selenium should I consume via dietary supplements??

According to the federal Institute for Risk Assessment, you should not exceed 45 milligrams of selenium via dietary supplements [9].

per day.

Can selenium tablets cause side effects?

Selenium only benefits your health when taken in the right amount. Thus, a daily intake of more than 300 micrograms of selenium through dietary supplements can lead to health problems[12, 16]:

  • Fatigue
  • Hair loss, discolouration of the skin
  • Nausea, vomiting, diarrhoea
  • Bad breath (garlic breath)
  • Motor function disorders

If there is a surplus of selenium over a longer period of time, the risk of type 2 diabetes and even prostate cancer may increase[3].

Ingestion of selenium and vitamin E

Selenium and vitamin E mutually strengthen one another. On the Internet, you will often find recommendations that require the simultaneous intake of both nutrients. However, the German  Society for Endocrinology cautions against Selenium-Vitamin-E preparations: If there is an undiscovered selenium deficiency, the additional intake of vitamin E can increase the risk of prostate cancer in men. The use of such combination preparations should only occur after consultation with a physician. In a study published in the Journal of the National Cancer Institute, researchers observed that the risk was increased by 111 per cent [17-19].


Selenium and Zinc: Whether selenium and zinc should also be taken at the same time is still not clear. In a study involving rats, researchers were able to observe a negative effect on the prostate when taking selenium and zinc at the same time.[20].

Selenium test

If you are sufficiently supplied with selenium, can be determined via a blood sample. If selenium poisoning is suspected, a urine sample can provide clarity. Researchers are also trying to determine the status of selenium using hair and nail analyses. These methods are currently considered inappropriate because the results vary too greatly [21].

With a self-test like the cerascreen® Mineral Test, you can determine your selenium level with a small amount of blood from your fingertip. After evaluation in the laboratory, you will receive a result report with your selenium, zinc and magnesium values as well as individual recommendations for action to improve your values.

Selenium and thyroid

The thyroid could not function properly without selenium. Can taking additional selenium help with thyroid problems?

Does selenium help in the treatment of thyroid disorders?

It is not yet clear whether selenium is effective against thyroid diseases such as Hashimoto's. In one study, pregnant women used selenium, which had a positive effect on hypothyroidism and Hashimoto's after birth. People with endocrine orbitopathy should also improve their symptoms with selenium supplementation[22-24].

Endocrine orbitopathy: In this disease, the eyeballs protrude strongly. The cause is an autoimmune reaction: the immune system attacks the body, in this case tissue in the eye socket. Many sufferers also suffer from hyperthyroidism.[25]


Selenium – at a Glance

What is Selenium?

Selenium is an essential trace element that is stored primarily in the muscles and thyroid gland.

What are the functions of selenium?

This trace element supports immune and thyroid functions as well as male fertility.

What is the daily requirement?

Men should consume 70 micrograms of selenium per day and women 60 micrograms. You can meet your daily selenium requirement with just one Brazil nut.

What are the symptoms of selenium deficiency?

Possible symptoms of selenium deficiency include fatigue, depressive moods, increased susceptibility to infections and thyroid problems.

What should I look for in selenium preparations?

Preparations containing the compound selenomethionine are best absorbed by the body. Do not use a combination of selenium and vitamin E as vitamin E may increase the risk of prostate cancer if selenium deficiency is not detected. The risk of cancer may also increase if you take additional selenium supplements with a sufficient selenium level. Selenium poisoning can lead to bad breath, hair loss and yellow skin.



  1. What is Selenium? | American Nutrition Association, http://americannutritionassociation.org/newsletter/what-selenium
  2. Chemistry International -- Newsmagazine for IUPAC, https://www.iupac.org/publications/ci/2011/3305/5_trofast.html
  3. Rayman, M.P.: The importance of selenium to human health. Lancet. 356, 233–241 (2000). doi:10.1016/S0140-6736(00)02490-9
  4. Elmadfa, I.: Ernährungslehre. Verlag Eugen Ulmer Stuttgart (2015)
  5. Bjørklund, G.: Selenium as an antidote in the treatment of mercury intoxication. Biometals. 28, 605–614 (2015). doi:10.1007/s10534-015-9857-5
  6. Selen, https://www.dge.de/wissenschaft/referenzwerte/selen/
  7. Paranuss - Lebensmittel-Warenkunde, https://lebensmittel-warenkunde.de/lebensmittel/fette-oele/samen-nuesse/paranuss.html
  8. Lebensmittel | DocMedicus Vitalstofflexikon, http://www.vitalstoff-lexikon.de/Spurenelemente/Selen/Lebensmittel.html
  9. Selen - ein guter Schutz für unseren Körper, https://www.verbraucherzentrale.de/wissen/lebensmittel/nahrungsergaenzungsmittel/selen-ein-guter-schutz-fuer-unseren-koerper-17732
  10. Selenmangel nimmt zu: Klimawandel hat Einfluss auf unser Essen, https://www.bzfe.de/inhalt/selenmangel-nimmt-zu-29778.html
  11. Ausgewählte Fragen und Antworten zu Selen, https://www.dge.de/wissenschaft/weitere-publikationen/faqs/selen/
  12. Die ganze Welt der Vitamine, Mineralstoffe und Enzyme. garant Verlag GmbH, Renningen (2016)
  13. Selen und Human-Biomitoring Stellungnahme der Kommission „Human-Biomonitoring“ des Umweltbundesamtes, https://www.umweltbundesamt.de/sites/default/files/medien/377/dokumente/selen.pdf
  14. Benton, D., Cook, R.: The impact of selenium supplementation on mood. Biol. Psychiatry. 29, 1092–1098 (1991)
  15. Nahrungsergänzungsmittel, https://www.bzfe.de/inhalt/pressemeldung-7874.html
  16. Barceloux, D.G.: Selenium. J. Toxicol. Clin. Toxicol. 37, 145–172 (1999)
  17. Selen und Vitamin E nur bei Mangel, https://www.deutsche-apotheker-zeitung.de/news/artikel/2014/05/02/selen-und-vitamin-e-nur-bei-mangel
  18. Selen und Vitamin E, https://www.bzfe.de/inhalt/pressemeldung-7020.html
  19. Selenium and Vitamin E Cancer Prevention Trial (SELECT): Questions and Answers, https://www.cancer.gov/types/prostate/research/select-trial-results-qa
  20. Daragó, A., Sapota, A., Nasiadek, M., Klimczak, M., Kilanowicz, A.: The Effect of Zinc and Selenium Supplementation Mode on Their Bioavailability in the Rat Prostate. Should Administration Be Joint or Separate? Nutrients. 8, (2016). doi:10.3390/nu8100601
  21. Problematik, Klinik und Beispiele der Spurenelementvergiftung - Selen, https://www.gtfch.org/cms/images/stories/media/tk/tk79_1/mueller1.pdf
  22. van Zuuren, E.J., Albusta, A.Y., Fedorowicz, Z., Carter, B., Pijl, H.: Selenium supplementation for Hashimoto’s thyroiditis. Cochrane Database Syst Rev. CD010223 (2013). doi:10.1002/14651858.CD010223.pub2
  23. Ventura, M., Melo, M., Carrilho, F.: Selenium and Thyroid Disease: From Pathophysiology to Treatment. Int J Endocrinol. 2017, (2017). doi:10.1155/2017/1297658
  24. Drutel, A., Archambeaud, F., Caron, P.: Selenium and the thyroid gland: more good news for clinicians. Clin. Endocrinol. (Oxf). 78, 155–164 (2013). doi:10.1111/cen.12066
  25. Pschyrembel Online | endokrine Orbitopathie, https://www.pschyrembel.de/endokrine%20Orbitopathie/K0FR6/doc/

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