Selenium as one of the essential elements needed for the proper functioning of the body

Selenium is a trace element that has a significant impact on the proper functioning of the human body. Among other things, it ensures the proper functioning of the thyroid gland and the immune system. Recent studies have shown that maintaining its proper level may affect the risk of certain cancers. Where can we find selenium and how should we supplement it? You will find the answers to these and other questions in the following article.

Sources of selenium

Selenium, designated Se in the periodic table of elements, is found in trace amounts in water and soil. This is how it enters the food chain. In plants, unlike animals, where selenium occurs only in organic form, it occurs in inorganic form as selenates and selenides and in organic form as selenomethionine.

The main sources of selenium in the human diet are cereal products, dairy products, fruit, vegetables, meat and fish. Broccoli, white cabbage, garlic, onions and legumes have the highest selenium content among vegetables. An interesting fact is that the final amount of Se contained in vegetables depends on the quality of the soil in which they were grown. Unfortunately, the selenium content in Polish soils is very low, so they should be supplemented with fertilisers containing selenium. Due to the fact that the amount of selenium in vegetables may ultimately be negligible, animal products become its primary source. For people who do not eat meat, nuts, especially Brazil nuts, and mushrooms can be a good alternative.

Properties of selenium

Selenium plays a very important role in the human body, which is why it is so important to maintain the correct level of this element. Selenium is essential for the functioning of enzymes and the protection of cells against toxins and free radicals. It also has a huge impact on the functioning of the thyroid gland. In addition, it can be used as an adjunctive treatment for pain in rheumatoid arthritis. Proper selenium levels are essential for the treatment of depression, although it is worth remembering that excess selenium can also have unpleasant effects on our psyche and the entire nervous system.

Mineral and organic selenium

The composition and chemical form of the ingredients in a dietary supplement are the most important factors that affect its absorption by our body. Dietary supplements containing selenium can come in two forms:

• organic, containing L-selenomethionine or selenocysteine,
• inorganic, containing selenine or sodium selenite.

Organic selenium, mainly in the form of L-selenomethionine, is considered to be the best absorbed form of the element. Selenium in the form of inorganic compounds is mostly excreted from our body. However, it is worth noting that sodium selenite is absorbed faster than organic forms.

Selenium requirements

Although the recommendations of medical societies are not always consistent, in the case of selenium supplementation, they clearly and explicitly indicate its normal intake. The recommendations for Se intake are based on scientific studies that have shown its widespread deficiency. An adequate supply of selenium is considered to be a value that ensures the correct concentration of this element in the blood. An interesting fact is that due to significant differences in the occurrence of selenium in different parts of the world, the recommended intake values vary. For example, the National Institute of Health in the United States recommends that adults consume 55 μg of selenium per day, while the German Nutrition Society recommends 70 μg for men and 60 μg for women.

In Poland, the recommended daily intake of selenium for adults is 55 μg. It should be remembered that the requirement for this element changes in pregnant and breastfeeding women, as they must also take into account the needs of their child, whose requirement for selenium during foetal life is approximately 2 μg per day. For infants up to four months of age, this is approximately 10 μg per day, and between four and twelve months of age, it is approximately 15 μg per day.

Children aged 1 to 9 should consume approximately 20-30 µg of selenium daily, and 40 µg daily at the age of 12-13.

The table below shows the daily selenium requirement by age.

Age
Infants up to 4 months old	10 μg per day
Infants aged 4 to 12 months	15 μg per day
children aged 1-3 years old	20 μg per day
children aged 4-6 years old	30 μg per day
children aged 7 to 9 years old	30 μg per day
children aged 10 to 12 years old	40 μg per day
children aged 13 to 15 years old	55 μg per day
children aged 16-18 years old	55 μg per day
adults over 18 years old including: pregnant women including: breastfeeding women	55 μg per day 60 μg per day 70 μg per day

Excess selenium

Excess selenium in the body can lead to poisoning, known as selenosis. It can occur in people who consume this element in significantly excessive amounts, around 400 μg per day, over a long period of time. This condition manifests itself in hair loss, garlic breath, discolouration of the nail plate, neurological disorders and diarrhoea. Selenium poisoning is a serious condition that can lead to cirrhosis of the liver, pulmonary oedema and death. One of the adverse effects of prolonged selenium supplementation may also be diabetes.

Selenium and zinc

For most of us, selenium is automatically associated with zinc. This analogous way of thinking is a very good way to support our immune system. Many dietary supplements are designed in this way, and advertisements reinforce this correlation. This is because both selenium and zinc strengthen the immune system by increasing antibody production and white blood cell activity. Of course, there is no absolute necessity to combine these two elements, but supplementing them may be beneficial for most people. Dietary supplements containing zinc and selenium should be of particular interest to people who do not eat meat, the elderly, and anyone who does not follow a properly balanced daily diet.

What else can selenium be combined with?

In addition to the aforementioned zinc, selenium should be combined with yeast enriched with this element, which contains selenomethionine, B vitamins and vitamin A. In addition, the absorption of selenium is also increased by vitamin C, vitamin E and methionine.

Furthermore, it has been shown that selenium contained in plant products is better absorbed by the human body. However, as mentioned above, plant products contain less selenium than animal products.

Bibliography

Ignacy Eichstaedt: The Book of Elements. Warsaw: Wiedza Powszechna, 1973.

Polish Pharmacopoeia X, Polish Pharmaceutical Society, Warsaw: Office for Registration of Medicinal Products, Medical Devices and Biocidal Products, 2014.

Wojciech Wasowicz Selenium status of low-selenium area residents: Polish experience, Toxicology Letters, 2003.

Joanna Kuczyńska, Marek Biziuk: Biogeochemistry of selenium and its monitoring in biological materials of human origin: ‘Chemistry and Environmental Engineering A’, 14 (S1), 2007.

Henryk Gertig, Juliusz Przysławski, Bromatology. An outline of food and nutrition science, 1st edition, Warsaw: PZWL Medical Publishing House, 2007.