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
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
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
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
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
** 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.