Selenium is an essential trace element responsible for many important functions in the body, including supporting the immune system, regulating thyroid function, and protecting cells from oxidative stress. It acts as a component of antioxidant enzymes that protect cells from free radical damage. Selenium is found in various foods such as meat, fish, nuts, and grains, but is also available as a dietary supplement. In this article, you'll learn why selenium is so important, its health benefits, and how to use it safely.
What is selenium?
Selenium is an essential trace element required in small amounts for human health. It is a central component of selenoproteins, which have antioxidant and anti-inflammatory functions. These selenoproteins play a role in regulating thyroid hormones and supporting the immune system. Selenium also contributes to fertility and plays a key role in DNA synthesis and reproduction [1].
Synonyms for selenium
Selenium is often referred to in dietary supplements as selenomethionine , selenocysteine , or sodium selenite . These forms differ in their bioavailability, with selenomethionine being considered the most readily absorbed form [2].
Where does selenium come from?
Selenium occurs naturally in soils, meaning the selenium content in foods varies by region. Good natural sources of selenium include meat, fish, eggs, Brazil nuts, and whole grains. Brazil nuts are particularly rich in selenium and can meet daily needs with just a small portion. Because the selenium content in soils varies, the amount of selenium in plant-based foods can vary [3].
How is selenium produced?
Selenium in dietary supplements is often synthetically produced or extracted from natural sources such as plants or animal products. Selenium is often presented in supplements as selenomethionine or sodium selenite. These forms are chemically stable and easily absorbed by the body to meet daily selenium needs [4].
Health benefits of selenium
Selenium and the immune system
Selenium is crucial for immune system function because it supports the production of selenoproteins, which have anti-inflammatory effects and strengthen the immune system. Adequate selenium status can help reduce the risk of infections and improve the immune response. Studies have shown that people with selenium deficiency are more susceptible to infections and have a poorer immune response [5].
Selenium and the thyroid
Selenium plays a key role in supporting thyroid function. It is involved in the conversion of the thyroid hormone T4 into its active form T3. A selenium deficiency can impair thyroid function and increase the risk of thyroid diseases such as Hashimoto's thyroiditis. Studies suggest that selenium supplements may help relieve the symptoms of autoimmune thyroid diseases and support overall thyroid health [6].
If you are interested in thyroid health, it is worth taking a look at this article:
Iodine – essential for thyroid and metabolism.
Selenium and antioxidants
As a powerful antioxidant, selenium helps protect cells from oxidative stress caused by free radicals. Selenium is an essential component of the enzyme glutathione peroxidase , which protects cells from damage caused by environmental factors such as air pollution, UV radiation, and smoking. By neutralizing free radicals, selenium contributes to the prevention of chronic diseases such as cardiovascular disease and cancer [7].
Selenium and fertility
Selenium plays an important role in male and female fertility. It supports sperm production and contributes to maintaining normal sperm quality. Selenium deficiency can impair fertility and increase the risk of pregnancy complications. In women, selenium contributes to the health of the reproductive system and may reduce the risk of miscarriage [8].
Selenium and heart health
Selenium may also contribute to improved heart health by reducing inflammation and oxidative stress, which can lead to cardiovascular disease. Some studies suggest that low selenium status is associated with an increased risk of coronary heart disease. Through its antioxidant effects, selenium may help support blood vessel health and reduce the risk of heart attacks [9].
Selenium and cognitive function
Recent research suggests that selenium may play an important role in maintaining cognitive function in old age. It is thought that the antioxidant protection provided by selenium may help prevent or slow the progression of neurodegenerative diseases such as Alzheimer's disease. Studies show that people with higher selenium status have better cognitive performance and a lower risk of cognitive impairment [10].
How does selenium work in the body?
Selenium works in the body as a component of selenoproteins, which have antioxidant and anti-inflammatory properties. These proteins protect cells from free radical damage and contribute to the regulation of thyroid hormones. Selenium also plays an important role in DNA synthesis and the repair of cellular damage, making it an essential trace element for overall health [11].
Recommended dosage and use of selenium
What is the recommended dosage?
The recommended daily intake (RDA) of selenium for adults is approximately 55 micrograms per day. Pregnant and breastfeeding women have a slightly increased need of approximately 60 to 70 micrograms per day. In certain cases, such as thyroid disorders or to support the immune system, higher doses of up to 200 micrograms per day may be recommended, but this should always be done under medical supervision [12].
When should you take selenium?
Selenium can be taken at any time of day, preferably with food to improve absorption. Selenium supplements are available in tablet, capsule, and drop form. It is important not to exceed the recommended dosage, as excessive selenium intake can lead to side effects [13].
Side effects and safety of selenium
Is selenium safe?
Selenium is safe and well-tolerated in recommended amounts. However, excessive intake (more than 400 micrograms per day) can cause side effects such as nausea, hair loss, fatigue, and nerve damage. Chronic selenium overdose, known as selenosis , can cause serious health problems. Therefore, it is recommended to consult a physician before taking selenium supplements, especially at higher doses [14].
What are the side effects of selenium?
Potential side effects of excessive selenium intake include stomach upset, hair loss, brittle nails, a metallic taste in the mouth, and nerve damage. At very high doses, selenium can be toxic and cause serious health problems. It is recommended to limit daily intake to 55 to 200 micrograms to minimize the risk of side effects [15].
Selenium compared to other trace elements
Selenium vs. Zinc
Both selenium and zinc are essential trace elements that play important roles in the immune system and antioxidant protection. While zinc is particularly important for wound healing and cell division, selenium supports thyroid function and protects cells from oxidative stress. Both minerals are essential for health but act differently in the body [16].
Selenium vs. Iron
Selenium and iron are both important for oxygen transport and cellular function, but they serve different roles. Iron is crucial for hemoglobin formation and oxygen transport in the blood, while selenium supports cellular function through its antioxidant properties. Both minerals are necessary for health, but excessive intake of one can impair the absorption of the other, so a balanced ratio is important [17].
Natural sources of selenium
Selenium is found in many foods, including meat, fish, seafood, eggs, nuts, and whole grains. Brazil nuts are particularly rich in selenium and can meet daily needs with just a small amount. Fish such as tuna, salmon, and sardines are also good sources of selenium. Because the selenium content in plant foods varies depending on soil quality, people in selenium-deficient regions may have difficulty obtaining sufficient selenium through their diet [18].
Selenium in dietary supplements
Selenium supplements are available in various forms, including selenomethionine, sodium selenite, and selenocysteine. Selenomethionine is considered the most bioavailable form and is a common choice for dietary supplements. These supplements are often used to support thyroid function, fertility, and the immune system. It is important to adhere to the recommended dosage to avoid side effects [19].
Final thoughts on selenium
Selenium is an essential trace element that is vital for thyroid function, the immune system, and the body's antioxidant defenses. It protects cells from oxidative stress, supports fertility, and contributes to heart health. For people looking to improve their thyroid function, strengthen their immune system, or protect their cells from damage, selenium is a valuable supplement that can be obtained either through food or supplements.