The trace mineral selenium was considered an irrelevant nutrient as recently as three decades ago, but now scientists have discovered that selenium is actually crucial to the health of humans and that the benefits of selenium in helping to protect the body against a wide range of damaging diseases needs more investigation.

Selenium’s rise from an irrelevant mineral to a crucial trace element has occurred as a result of studies indicating its role in regulating metabolism, cell manufacture, enhancing reproductive efforts, neutralising damaging free radicals and protecting the body against infection. In addition to these benefits, selenium is the only trace element that is incorporated into our genetic material. Selenocysteine is a specific amino acid that is incorporated into numerous proteins in our bodies under the direction of the genetic code.

What are the food source of selenium?

Food sources of selenium include chicken, meat, grains, fish, and dairy products. However, most of the foods we ingest contain very low levels of selenium especially if you live in Europe. The reason for this is because selenium is a trace mineral that is extracted by plants from the soil and therefore its availability is largely determined by soil quality. Unfortunately, most of Europe, China, and New Zealand are known for having selenium-deficient soils.

Selenium's benefits

The benefits of selenium are numerous since it is involved in the production of a wide variety of enzymes and hormones. It is this widespread involvement in the body's chemistry which results in the multitude of benefits. Selenium bonds with proteins in our bodies to create compounds known as selenoproteins. At least 25 unique selenoproteins exist within our bodies which play an important role in many processes from protecting us against free radical damage through to activating thyroid hormone release.^4,5

The major benefits of selenium include its ability to protect our body from free radical damage. Selenium combines with the body’s natural antioxidant, glutathione, to form powerful compounds known as glutathione peroxidases. Glutathione peroxidases are compounds that convert hydrogen peroxide and other damaging compounds into water or harmless alcohol. Selenium also combines with a specific protein to form a compound referred to as Selenoprotein P. This particular protein helps to protect the circulatory system including the heart and all the blood vessels from damage.

The other benefit of selenium is that it reactivates vitamins C and E back to their active state. Vitamins C and E work to neutralise free radicals and without selenium, these neutralised compounds would be excreted out including the vitamins C and E. By binding with the toxic molecules, vitamins C and E are put back into their active state so that they can attack more free radicals and protect our bodies.³

Selenium plays a crucial role in the proper functioning of the immune system. Selenium is required to signal cytokines, which are compounds that alarm your immune system to get to work. Additionally, selenium has been shown to prevent viral mutation of many species and thus prevent recurring infections.

There is a body of evidence showing the protective effect of selenium against cell mutation which has recently been reinforced by the results of a number of important studies in the US and Finland. Within the UK, dietary selenium levels are considerably lower than in the US, and have fallen very significantly in recent years. Levels now stand at around half the Government’s defined Reference Nutrient Intake which for the UK is 70 mcg for men and 60 mcg for women.

Confirmation of the viability of preventing cell mutation by using a dietary supplement of selenium would have tremendous potential for reducing the various forms of these diseases at relatively low cost. Researchers at the University of Arizona conducted a study involving 1300 patients, some of who were given 200 mcg of selenium over a decade, found more than 50% reduction in certain cell mutation diseases when compared to the placebo group.

The thyroid gland holds the largest concentration of selenium of any organ in the body. Three different selenium-bound proteins are responsible for making active thyroid hormone available in circulation. Selenium is therefore essential for all the processes carried out by the thyroid gland including metabolism, normal growth and development. This is aside from the link between thyroid hormones and all the other hormones within our body. Thyroid hormone deficiencies affect most other hormonal glands in the body.^4,5

Although the benefits of selenium in protecting the cardiovascular system remains unclear, it is theorised that its anti-inflammatory and antioxidant properties may help protect the heart, although more research needs to be carried out to confirm this.^6,7,8

We now have access to high quality selenium supplements that should contain L-selenomethionine, the most absorbable form of selenoproteins. The selenium supplement that I favour is Super Selenium Complex by Life Extension, take one capsule with food. This supplement not only contains L-selenomethionine but also contains other selenoproteins which all have varying roles in the body.¹

In order to obtain the benefits of selenium and to avoid side effects, it is unwise to exceed the recommended daily dose which is between 200mcg and 400mcg so do check your supplements such as multivitamins and antioxidants for their selenium content.  Selenium contributes to the normal function of the immune system and towards the maintenance of normal hair and nails.

References: 

1. Zhonghua Yu Fang Yi Xue Za Zhi. Chinese Journal of Preventive Medicine. 2010;44(2):119-22.
2. Cancer Research. 2003;63(20):6988-95.
3. Science. 1973;179(4073):588-590.
4. Best practice & research Clinical endocrinology & metabolism. 2009;23(6):815-827.
5. The Journal of Nutrition. 2003;133(5):1457S-1459S.
6. Ewha Med J. 2017;40(1):17-21.
7. Nutrients. 2015;7(5):3094-3118.
8. Journal of Inorganic Biochemistry. 2015;153:1-12.

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