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Selenium - a mineral crucial to health

4 min read

As recently as three decades ago, Selenium was considered an irrelevant nutrient however scientists have now discovered that it's nutritionally essential for humans and plays a key role in regulating metabolism, cell manufacture, enhancing fertility, neutralising damaging free radicals and protecting the body against infection.

Worryingly, 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.

Selenium as an antioxidant

Selenium is the only trace element that is incorporated into our genetic material - selenium bonds with proteins in our bodies to create compounds known as selenoproteins, there are at least 25 unique selenoproteins that exist within our bodies.  

Selenium in the form of selenocysteine combines with an enzyme called glutathione peroxidase, which plays an important role in protecting cell membranes from damage. Glutathione peroxidases are compounds that convert hydrogen peroxide and other damaging compounds into water or harmless alcohol.

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.

Selenium and cardiovascular disease

Selenium 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.

Selenoproteins help prevent the oxidative modification of lipids, reducing inflammation and preventing platelets from clustering together. For these reasons, experts have suggested that selenium supplements could reduce the risk of cardiovascular disease or deaths associated with cardiovascular disease.

Although selenium’s role in protecting the cardiovascular system remains unclear, it is theorized that selenium’s anti-inflammatory and antioxidant properties may help protect the heart, although more research needs to be carried out to confirm this.

Selenium plays key role in 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.

Many studies suggest that the body needs selenium in order for the immune system to work properly. Selenium, along with other minerals, can help build up white blood cells, which boosts the body's ability to fight illness and infection. One study suggested that when elderly people took zinc and selenium supplements, their immune systems responded better to the flu vaccine than those who took placebo.

Selenium and thyroid health

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.

Selenium concentrations in the body decline with age

Deficient selenium concentrations might be associated with age-related declines in brain function, possibly due to decreases in selenium’s antioxidant activity.

Researchers have evaluated whether taking an antioxidant supplement containing selenium reduces the risk of cognitive impairment in elderly people. A study on 4,447 participants aged 45 to 60 years carried out in France found that, compared with placebo, daily supplementation with 120 mg ascorbic acid, 30 mg vitamin E, 6 mg beta-carotene, 100 mcg selenium, and 20 mg zinc for 8 years was associated with higher episodic memory* and semantic fluency** test scores 6 years after the study ended. However, selenium’s independent contribution to the observed effects in this study cannot be determined.

* Episodic memory is the memory of autobiographical events (times, places, associated emotions, and other contextual who, what, when, where, why knowledge) that can be explicitly stated.
** Verbal fluency tests are a kind of psychological test in which participants have to say as many words as possible from a category in a given time (usually 60 seconds). This category can be semantic, such as animals or fruits, or phonemic, such as words that begin with letter p.

Where can you get Selenium from?

Selenium is found in foods including chicken, meat, grains, fish and dairy products. However most of the foods we ingest contain very low levels of selenium especially in Europe. This is because the selenium content of plant food is dependent upon the selenium content of the soil in which it's grown - for the UK and Europe this is generally low.  In fact most of Europe, China and New Zealand are known for having selenium deficient soil. The amount of selenium in animals foods is dependent upon the feeding patterns of livestock.

High quality selenium supplements are now widely available however it is important not to exceed the recommended daily dose (between 200 mcg and 400 mcg) so do check your supplements such as multivitamins and antioxidants for their selenium content. Furthermore, Selenium can interact with certain medications, and some medications can have an adverse effect on selenium levels so if you are considering a supplement you should discuss with your health care provider first.

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A healthy balanced diet is the best way to consume all the nutrients we need. Sometimes however this isn't possible and then supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying any supplements or herbal medicines.