Selenium was discovered in 1817, but its role in our body began to be studied much later, in the middle of the 20th century. Today, it is known that many organs and systems cannot function properly without selenium. However, this mineral should not be perceived as a “magic pill” that can solve all health problems.
What is selenium
Selenium is a trace element that is vital for the body of women and men. The term “trace element” means that we need it in microscopic doses. However, consuming too much or too little selenium can have negative effects on health.
Selenium is widely distributed in nature: it is present in water and soil, in plant and animal products. We get it from food and food supplements, so the content of this microelement in our body largely depends on the region we live in and what we eat. Most of the selenium reserves are stored in muscle tissue, and its highest concentration is found in the thyroid gland.
The selenium content in the body is usually determined by examining its concentration in the blood serum. Normal values are considered to be 23–190 μg/l, a deficiency is diagnosed if the selenium level is below 23 μg/l.
There is an analysis that evaluates the concentration of the microelement in hair and nails. This indicator allows you to understand what the selenium level has been for several months and even years.
Useful information about selenium
| Daily requirement of selenium for women and men over 19 years old | Recommended Dietary Allowance 55 mcg 3 |
| Daily requirement of selenium for pregnant and lactating women | for pregnant women 60 mcg, for nursing women 70 mcg 3 |
| What functions does selenium perform in the body? | • provides antioxidant protection and strengthens the immune system; • supports cognitive functions, and normal functioning of the thyroid gland, reproductive system, muscles, and joints |
Benefits of Selenium
First of all, selenium is needed by the body of women and men for the production of selenoproteins – protein compounds that participate in many vital processes, including hormone synthesis, metabolism, and immune function.
For the thyroid gland
Selenium helps regulate the activity of thyroid hormones and has a positive effect on its functioning. Maintaining normal selenium levels in the body can prevent some thyroid diseases, such as Graves’ disease and Hashimoto’s autoimmune thyroiditis .
For the immune system
The effect of selenium on immunity has not been fully studied, research is ongoing. However, it is known that selenium enhances the work of immune system cells ( lymphocytes and macrophages), which fight infectious agents and destroy cancer cells formed in the body. There is evidence that selenium reduces the risk of developing malignant neoplasms in the liver in patients with hepatitis B and C. However the role of selenium in the prevention of other types of cancer (for example, bowel and prostate) has been studied but has not been proven.
Selenium is an essential nutrient for people with HIV infection. When plasma selenium levels decrease, so do the numbers of CD4 lymphocytes, the white blood cells that are responsible for the immune response to infections. Selenium facilitates the division of lymphocytes into different functions, thereby improving the function of our immune system.
This feature helps reduce the number of hospitalizations in people with HIV, especially for co-infections such as mycobacterial infections. Therefore, it can be said that selenium prevents the progression of HIV to AIDS.
For the cardiovascular system
Selenium is involved in the synthesis of a special enzyme, G-Px, which protects the body’s cells from destruction by free radicals. If there is not enough selenium in the body, the cells become more vulnerable, weaken, or die. This can lead to heart and vascular diseases. People with normal selenium levels have a lower risk of cardiovascular diseases, as shown by research results.
For the reproductive system
Selenium is very important for male reproductive health. It is involved in the biosynthesis of testosterone and promotes the formation and development of normal spermatozoa. Testicular tissue contains significant concentrations of selenium, which is responsible for maintaining sperm quality. And low selenium levels are often associated with male infertility .
For the nervous system and brain
With age, the level of selenium in the body decreases. It is assumed that this is one of the factors in the development of diseases such as Parkinson’s disease, Alzheimer’s disease, and multiple sclerosis.
Selenium as an antioxidant can prevent damage to brain cells and the nervous system, and therefore prevent a decrease in cognitive functions – memory, attention, and learning ability. Research is ongoing, but scientists believe that a sufficient amount of this microelement in the diet can maintain normal brain function.
Harm of selenium
Selenium is necessary for the proper functioning of our body, but if taken in excess quantities, side effects are possible – both fairly harmless and very dangerous.
The most common side effects of overdose are:
- unpleasant “garlic” smell from the mouth;
- fatigue;
- metallic taste in the mouth ;
- hair loss;
- nausea.
Taking too much selenium over a long period can lead to heart problems and kidney failure. In severe cases, death is possible.
It is important to keep in mind that selenium supplements may interact with other medications and supplements you are taking. Selenium may affect the absorption of drugs such as antacids (heartburn medications), oral contraceptives, corticosteroids, statins (cholesterol-lowering drugs).
Some studies have shown that selenium supplements may be associated with the development of squamous cell skin cancer. Therefore, people who are at risk for this disease should not take selenium supplements.
Which selenium is the best
Selenium supplements are most often available in capsule and tablet form. Selenium in dietary supplements comes in organic and inorganic forms. Both forms can be good dietary sources of selenium, but each has its own characteristics .
Organic forms of selenium are selenomethionine and selenocysteine. It is in this form that the microelement is present in food products of plant and animal origin. In food additives, selenomethionine is most often used, from which our body can absorb up to 90% of selenium.
Inorganic forms of selenium – selenate and selenite – are naturally found in soil. In food supplements, sodium selenite is most often found, which is absorbed by our body by about 50% . The advantage of supplements with selenite is a lower price.
There is a yeast and yeast-free form of organic selenium. Yeast selenium is obtained from yeast fungi grown on a selenium-enriched nutrient medium. The fungi grow, absorb selenium and convert it into an amino acid, which is used to make biologically active supplements. A significant disadvantage of the yeast form is its ability to cause allergic reactions and fermentation in the intestines.
The yeast-free form of selenium is considered safer. It is obtained in a similar way (from yeast fungi grown on a nutrient medium). But such selenium undergoes additional processing, during which it is purified from the cell membranes of fungi, and the resulting amino acids are broken down into short chains. In this form, the microelement is well absorbed and is harmless for people prone to allergies.
Instructions for use of selenium
The microelement should not be taken uncontrollably – that is, by everyone and in high doses. We will tell you who can benefit from selenium and who is not recommended to take it, and also explain some rules for taking it.
Daily dose of selenium for women and men
The recommended dietary allowance of selenium for adult men and women aged 19 years and older is 55 micrograms per day .
Who can take selenium?
Selenium supports many functions of our body, but dietary supplements with it should be prescribed by a doctor. Additional intake of the microelement can be useful for thyroid diseases, such as subclinical hypothyroidism and autoimmune thyroiditis. By replenishing selenium deficiency, it is possible to reduce the manifestations of the disease .
Selenium supplements may help people with age-related diseases (such as Alzheimer’s disease) that are accompanied by memory and attention impairment . Combined selenium and other antioxidants are recommended for people with heart and vascular disease or a high risk of such diseases .
Who should not take selenium
Selenium supplements are contraindicated for people with individual intolerance and those whose selenium deficiency has not been confirmed by laboratory tests. Selenium should not be taken by patients with blood clotting disorders and severe kidney and gastrointestinal diseases.
What time of day is best to take selenium
Morning, afternoon and evening, depending on personal preference. The time of administration does not matter.
When is it better to take selenium – during, before or after meals
There are no strict restrictions, so take selenium whenever it is convenient for you. But it is still better to do it during meals – this way you will not forget about taking it and will be able to avoid possible stomach problems.
Popular Questions and Answers
Doctor of Medical Sciences, physician of integrative and anti-aging medicine Svetlana Kanevskaya answers popular questions about this important microelement .
Why take selenium?
How to understand that the body lacks selenium?
Severe selenium deficiency is most often associated with the following conditions:
• Keshan disease, a type of cardiomyopathy or heart muscle disease (causing shortness of breath, swelling, dizziness, and heart failure);
• Kashin-Beck disease, a form of osteoarthritis that causes joints to become deformed, painful, and stiff.
Severe selenium deficiency can cause nausea, vomiting, headaches, confusion, seizures, and coma.
People at risk of selenium deficiency include those living in areas with low selenium levels and those who eat a predominantly plant-based diet (vegetarian or vegan). Regions with low selenium levels include parts of China, North Korea, and Russia (Siberia).
The risk of selenium deficiency is higher in HIV patients, who often develop diarrhea and loss of appetite during the disease, which means that the absorption of nutrients is impaired.
What foods contain a lot of selenium?
List of foods rich in selenium:
• Brazil nuts;
• fin fish and shellfish;
• beef;
• chicken;
• fortified cereals;
• whole grain bread;
• beans and lentils.
What diseases occur with selenium deficiency?
Cardiovascular system
Severe selenium deficiency can lead to Keshan disease, a type of congestive cardiomyopathy with symptoms such as heart failure, enlarged heart, electrocardiogram abnormalities, and cardiogenic shock. The disease primarily affects children and women of reproductive age.
Keshan disease was first discovered in areas of China with low selenium levels. The incidence rate was very high (50%), and fatal outcomes were common. The disease was complicated by chemical exposure and the presence of the Coxsackie virus. Selenium supplements, such as salt fortified with this microelement, have shown promising results in the fight against Keshan disease.
Endocrine system
Selenium is essential for the normal functioning of the thyroid gland. Its deficiency increases the risk of developing autoimmune thyroiditis and decreased thyroid function.
Immune system
Selenium has immunomodulatory activity, so its deficiency weakens the immune defense. It has also been observed that selenium deficiency causes benign viruses to transform into more dangerous pathogens within the human body. In China, for example, there is a “selenium deficiency belt” where new strains of influenza periodically appear. This fact highlights the relationship between selenium deficiency and the immune response.
Musculoskeletal system
Kashin-Beck disease is a debilitating condition that causes deformities of bones, cartilage, and joints, leading to enlarged joints and limited mobility. This disease is especially common in Tibet, China, Siberia, and North Korea. The origins of this disease are multifaceted, with selenium deficiency being one of the causes.
Neurological and psychiatric systems
Research has shown that insufficient selenium intake can contribute to depressive mood and increased aggressive behavior. In addition, it has been observed that selenium deficiency affects the rate of metabolism of certain neurotransmitters, chemicals that transmit signals from nerve cells to other cells in the body.
