Selenium – essential element

Selenium is a chemical element with the symbol Se and atomic number 34. It is a metalloid (more rarely considered a Non Metal) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic. It seldom occurs in its elemental state or as pure ore compounds in Earth's crust. Selenium (from Ancient Greek σελήνη (selḗnē) 'moon') was discovered in 1817 by Jöns Jacob Berzelius, who noted the similarity of the new element to the previously discovered tellurium (named for the Earth).

Selenium is a trace element. It occurs in the earth's crust at 0.05 ppm as an impurity in some sulfide ores. Selenium is one of the essential micronutrients and must be supplied in the diet. The content of selenium in food products varies greatly, which is associated with large differences in the selenium content of soil and water in different parts of the world. Soils in Poland are considered poor in selenium. Therefore, there is little selenium in water and plants, and consequently also little in the food consumed.

Selenium sources in food

The amount of selenium in food depends on on the selenium content in the environment (water, soil, plants) from which the food comes. The distribution of selenium (Se) in the earth's crust is uneven. Soils of some areas of Russia, USA, Venezuela contain very large amounts. Soils of New Zealand, some areas of China, West Korea, Siberia and Europe have very low concentrations. Selenium deficiency occurs in regions with sparse presence of rock materials. These include the northeastern soils of the USA, northern Germany, Denmark, Poland and the Baltic states, central Russia from the Urals to all of Siberia, inclusive. Se concentrations in volcanic rocks are estimated at 120 µg/g, soils contain 0.005-1200 µg/g, most often within the range of 0.1-10 µg. In regions poor in selenium, its concentration is at the level of 0.005–2.0 µg. Plants, drawing selenium from the soil, provide it to all organisms. For these environments, selenium is an important trace element, indispensable for proper functioning, it can also be a factor whose excess or deficiency causes undesirable effects. (Source: Advanced soil geochemical atlas of England and Wales Selenium in England and Wales UK Soil Observatory

Food sources of selenium: cereals, meat, eggs, dairy products, fish and shellfish. Not all foods are a good source of selenium, because this element is not well absorbed in the digestive tract in every form. The basic role in bioavailability is played by the chemical form of selenium. Selenium obtained from yeast is characterized by the highest bioavailability. In addition, the absorption of selenium is supported by some proteins, amino acids and vitamins (mainly A, E, C). The synergistic effect of selenium with vitamin E contributes to delaying the aging process and accelerating cell regeneration.


Selenium content in selected foods

Type of Food Selenium Content
in 100 Grams
  Brazil nuts
2700 μg
  Beef liver
124 μg
  Yellowfin tuna
80 μg
59 μg
  Chia seeds*
54 μg
49 μg
  Sunflower seeds
48 μg
  Chicken brest
41,5 μg
31 μg
26 μg
  Chicken egg, large approx. 65g
15 μg
  Brown rice
8,5 μg
7 μg

How much selenium do we need?

As with any element and vitamin, the amount of selenium we need depends on the following factors: (1) age, (2) physiological state, (3) health, i.e. diseases, etc., (4) diet (people following a meat-free diet are at higher risk of selenium deficiency). (5) where you live (some regions are more prone to selenium deficiency than others).

It is estimated that the UK lies in areas poor in selenium, which is why selenium deficiencies in the diet of English people are often observed. Therefore, selenium supplementation may be important in the English people diet, especially in the case of people with dietary restrictions (e.g. vegans and vegetarians), people suffering from chronic diseases of the digestive tract (such as Crohn's disease or ulcerative colitis) accompanied by impaired absorption and elderly people, as selenium absorption deteriorates with age. Smokers, alcohol drinkers and contraceptives may also be at risk of selenium deficiency.


The selenium requirement depending on age

Age Daily selenium requirement
in µg
  Infants up to 6 months of age
15 µg
  Infants and and small children up to 9 years of age
20 µg
  Children aged 10-12
40 µg
  Children over 13 years of age
50 µg
  Adult women
55 µg
  Adult men
60 µg
  Pregnant and lactating women
60 – 70 µg

*Salvia hispanica, one of several related species commonly known as chia, is a species of flowering plant in the mint family, Lamiaceae, native to central and southern Mexico and Guatemala. It is considered a pseudocereal, cultivated for its edible, hydrophilic chia seed, grown and commonly used as food in several countries of western South America, western Mexico, and the southwestern United States.

Moreover chia seeds contain valuable minerals for human health: iron, magnesium, zinc, phosphorus, as well as calcium and vitamins: E, B1, B3. Chia seed oil contains a very high concentration of omega-3 fatty acids - about 64%, as well as omega-6 fatty acids, which are in a beneficial for health and disease prevention ratio to omega-3.

Is selenium intake safe?

It is almost impossible to overdose on dietary selenium. But long-term use of too high doses of selenium supplements can lead to poisoning.

Toxic levels of selenium in the body (can cause a condition called selenosis) and can be the result of taking too much of this element in the form of supplements. If this happens, the following symptoms of poisoning may occur:

    • Pain in muscles and joints
    • Diarrhea, fatigue
    • Nail brittleness and hair loss
    • Metallic taste in the mouth
    • Skin redness
    • Respiratory problems
    • Increased risk of developing diabetes type 2

Why do we need selenium?

Selenium is an element thanks to which our body functions in an appropriate, harmonious and healthy mode. Although its properties are perhaps less widely known, it performs significant functions. According to EFSA (European Food Safety Agency), the health claims for selenium are as follows:
        (1) Keeping your hair in good condition (ID 281),
        (2) Keeping your nails in good condition (ID 383),
        (3) Keeping joints in good condition (ID 409),
        (4) Maintaining good thyroid function (ID 1292),
        (5) Protection of DNA, proteins and lipids from oxidative damage (ID 410, 1292)
        (6) Maintaining the proper functioning of the immune system (ID 1750)
in accordance of article 13 (1) Regulation (EC) No 1924/2006 of the European Parliament and of the Council of 20 December 2006 on nutrition and health claims made on foods.

  • It is a cofactor* of many enzymes (approx. 20)
  • Protects cells against free radicals (acts as an antioxidant)
  • Supports the body's immunity (protects against bacteria, fungi and viruses)
  • Maintains thyroid gland function
  • Maintains nervous system health (Parkinson's disease, Alzheimer's disease)
  • Maintains cardiovascular health
  • Maintains respiratory system health
  • Maintains immune system health

*Cofactors are chemicals that speed up certain chemical reactions. They are components of some enzymes that are necessary for the proper functioning of the body. Read more → Cofactor Biology dictionary


Selenium and Immune Health

Selenium is a microelement essential for the proper functioning of our body, including the immune system. Although selenium consumption in itself does not improve (does not stimulate) immunity, it has been conclusively shown that its deficiency negatively affects the functioning of the immune system. Selenium deficiency can cause many changes in the human immune system, the most important of which are:

    • Suppression of the host's immune response to bacterial or viral infection
    • Inhibition of biosynthesis of prostaglandins and immunoglobulins
    • Decreased activity of T lymphocytes, natural killer cells and macrophages
    • Reducing the body's ability to reject transplants and destroy cancerous tumors
    • Increased platelets aggregation

Selenium also affects chemotaxis, migration and fungicidal activity of phagocytic cells. Selenium supplementation in parenterally fed patients enhanced the humoral response by enhancing the proliferation and differentiation of B lymphocytes stimulated in vitro with mitogens.

Selenium and Circulatory System

There exists an impressive body of evidence about the several important functions of selenium and its selenoproteins in the cardiovascular system, which are mainly due to its well-known antioxidant characteristics. Although the role of selenium supplementation in the prevention of cardiovascular diseases is inconclusive, it is important to clarify if selenium deficiency leads to new health implications, particularly in relation to acute cardiovascular disease, where patients are exposed to myocardial I/R (ischemia / reperfusion) and increased oxidative stress.


Selenium and Thyroid Health

It is believed currently that for the proper functioning of the thyroid gland, apart from iodine, selenium, iron, zinc, copper and calcium are also necessary. Often only an adequate supply of one of these micronutrients (e.g. iodine) may reveal symptoms resulting from the deficiency of the others (e.g. iron or selenium). The thyroid gland, like the testicles and the brain, compared to other organs of the human body, is characterized by a high content of selenium, even in spite of its severe deficiency in the body.

Many important clinical data on the role of selenium supplementation in thyroid homeostasis were provided by research conducted in the 80s in Central Africa. In the population living in this part of the continent, symptoms of cretinism with myxedema were observed, manifested, among others, by mental retardation, inhibition of growth and sexual maturation, which, as studies showed, were related to iodine and selenium deficiency and the consumption of large amounts of food containing goitrogens (goit forming compounds).

Selen ↔ glutation

Peroksydaza glutationowa (GPX) to grupa enzymów wykazujących aktywność peroksydazy, których główną funkcją jest chronienie komórek przed utlenianiem przez nadtlenki powstające w trakcie procesów biochemicznych. Peroksydaza glutationowa redukuje zarówno nadtlenek wodoru, jak i nadtlenki organiczne. Oznaczana jest symbolem GPXn, gdzie "n" jest numerem izoenzymu. Peroksydaza glutationowa zawiera selenocysteinę. Pod wpływem nadtlenku reszta selenolowa Enz−SeH jest utleniana do kwasu selenenowego Enz−SeOH, który następnie reaguje z glutationem (GSH) z wytworzeniem selenylosulfidu Enz−Se−S−G. W reakcji z kolejną cząsteczką GSH odtwarzany jest enzym w formie zredukowanej, a glutation tworzy disiarczek glutationu, dimer GS−SG z mostkiem dwusiarczkowym.

Typical Symptoms of Selenium Deficiency

Jeśli chodzi o niedobór tego bardzo ważnego elementu dla naszego organizmu to należy wiedzieć, iż występuje on bardzo rzadko, najczęściej w przypadku poważnych zaburzeń we wchłanialności pokarmu z przewodu pokarmowego, żywieniu pozajelitowym czy stanu po usunięcia dużego fragmentu jelita cienkiego. Nie mniej jednak czasem może się to zdarzyć, chociaż w przypadku naszej typowej, polskiej diety byłoby to bardzo trudne. Typowymi objawami niewystarczającej ilości selenu w naszym organizmie są:

    • Heart failure
    • Thyroid gland malfunction
    • Brittleness and nails loss
    • Nausea, vomiting, sweating
    • Nervous system disorders
    • Hair loss
    • Bad breath

However, it should be remembered that when supplementing with selenium, the recommended doses must not be exceeded, because its too high concentration can have dangerous side effects. It should be noted that selenium is an element characterized by a relatively narrow safety margin between the state of deficiency, normal level and toxic dose. Thus, both deficiencies and excesses of this component are dangerous for the body. Excess selenium can cause toxic symptoms, the so-called selenosis and carry the risk of various types of cancer. That is why it is so important to react early enough to possible observations that may indicate a deficiency of this element, which is so important for the human body.

Selenium Supplementation in Children

Selenium is one of the few supplements whose excess can bring undesired symptoms and side effects. Therefore, selenium supplementation in children must be preceded by a clinical diagnosis of its deficiency, confirmed by determining the level of selenium in the blood. And the supplementation itself should take place under the supervision of a doctor.

Please also notice that Immulina +D3 syrup for children provides 10 µg of selenium, which is 33,5% RDA (recommended daily allowance).


If you would like to contact us:

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  (+48) 22 487 14 44
  (+48) 22 651 75 60

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