Author – Phoebe Chan – BSc (Hons) Nutrition and Human Health
Selenium is a trace element and part of the important micronutrients. It plays a role in many processes in the body including metabolism and preventing damage caused by infection and inflammation (1). Selenium deficiency may contribute to development of a form of heart disease, hypothyroidism and a weakened immune system (2). In this blog, we’ll explore how selenium benefits your body and how to include it in your diet safely.
What Is Selenium
Since selenium is a trace mineral, it means the body only needs a small amount of it. It is an essential component of various enzymes and proteins, called selenoproteins, that help make DNA and protect against cell damage and infections. These proteins are also involved in reproduction and the metabolism of thyroid hormones (3). In supplements, selenium generally comes in the following forms:
- Sodium selenate
- Sodium selenite
- Selenomethionine
- Selenocysteine
The two main forms of dietary selenium are organic selenium and inorganic selenium. Some forms of selenium, such as selenomethionine and selenocysteine, resemble the forms of selenium that are naturally present in food and the human body. Inorganic forms, such as sodium selenate, are hard for the body to process, which leads to decreased bioavailability (4).
In comparison to other minerals, selenium often gets overlooked. However, it is very important for a number of functions throughout the body. A deficiency can lead to immune function, increased risk of cardiovascular issues, infertility and cognitive decline (5).
Selenium and Immune Function
Selenium is key for our immune cells through helping them respond effectively to bugs and protect your body from infection. A deficiency in selenium can lower your resistance, while the right amount can boost white blood cell activity, antibody production and inflammation control. Therefore, people with low selenium are more likely to catch infections or have worse symptoms (6).
Selenium’s immunomodulatory effects are largely attributed to the diverse activity of selenoproteins. These proteins carry out redox reactions that protect cells from oxidative damage and regulate inflammation, thereby supporting optimal immune cell function. This enhances immune responses, including white blood cell activity and antibody production. As a result, adequate selenium levels help the body respond more efficiently to infections (7).
Selenium and Thyroid Health
Selenium has a major impact on thyroid health maintenance, despite it being required only in small amounts (8). It functions through selenoproteins, which are involved in critical enzymatic processes (9). In particular, iodothyronine deiodinases (DIO) are responsible for converting thyroxine (T4) into the active form triiodothyronine (T3), which regulates metabolism and other physiological functions. In addition, glutathione peroxidases (GPX1) protect the thyroid gland from oxidative stress by neutralising harmful reactive oxygen species produced during hormone synthesis (10).
Selenium is also important in autoimmune thyroid conditions such as Hashimoto’s thyroiditis (HT). This occurs when the immune system produces autoantibodies that attack the thyroid gland, leading to reduced hormone production. Adequate selenium levels may help reduce inflammation and autoimmune activity, thereby protecting thyroid cells and supporting normal hormone production (11).
Selenium as an Antioxidant
Selenium has important antioxidant properties that help protect cells from damage caused by oxidative stress, a condition resulting from an imbalance between free radicals and the body’s antioxidant defences. Oxidative stress can be influenced by factors such as pollution, poor diet and other environmental exposures. It is associated with the development of chronic diseases, including cancer and cardiovascular disease, as well as cognitive decline (12).
Selenium exerts its antioxidant effects as a key component of selenoproteins such as glutathione peroxidase (GPx). This enzyme helps neutralise free radicals and reactive oxygen species, thereby preventing cellular damage, reducing premature ageing and lowering the risk of oxidative stress-related diseases (13).
Dietary Sources of Selenium
Brazil nuts: one of the best sources of selenium. One ounce, or about six to eight nuts contains about 544 mcg. However, make sure to only eat a serving of Brazil nuts a few times a week to avoid selenium toxicity.
Fish: Yellowfin tuna contains about 92 mcg of selenium per 3 ounces, making it a great source of selenium. Sardines, shrimp, cod and salmon are also high in selenium.
Grains: grain products such as bread, pastas and cereals may provide high amounts of selenium. For example, refined grains, such as white bread ad pastas are enriched or fortified with selenium and other minerals.
Turkey: you can get 26 mcg of selenium from 3 oz of boneless turkey. Eating a turkey sandwich on fortified whole wheat bread can help you get extra selenium.
Chicken: per 3 oz of white meat such as chicken, this can provide you with approximately 22 mcg of selenium. This is a serving similar in size to a deck of cards, making it an easy way to add some selenium to your diet (14).
Recommended Intake and Safety Considerations
The Recommend Dietary Allowance (RDA) of selenium for adult men and women is 55 mcg daily. Women who are pregnant and lactating need about 60-70 mcg daily.
The Tolerable Upper Intake Level (UL) for selenium for all adults, including pregnant and lactating women is 400 mcg daily. A UL is the maximum daily intake unlikely to cause harmful effects on health.
Chronically high intakes of selenium can lead to health problems such as muscle tremors, hair loss, stomach upset and light-headedness. More severe outcomes such as heart attack, respiratory distress or kidney failure may also occur (15).
Conclusion
Selenium has many key benefits such as supporting immunity and thyroid health, as well as providing antioxidant protection. Most people can get enough selenium through their diet, with foods like Brazil nuts, grains, chicken and turkey being great sources. However, those who aren’t consuming enough should consider consulting a healthcare professional about a high-quality supplement.
Selenium may only be needed in small quantities, but its mighty in its health benefits.
FAQ’s (Frequently Asked Questions)
What is selenium and why is it important?
Selenium is an essential trace mineral that the body needs in small amounts to function properly. It plays a key role in supporting the immune system, maintaining thyroid health, and protecting cells from damage caused by oxidative stress.
How does selenium support the immune system?
Selenium helps regulate immune responses and supports the production of immune cells. It also reduces inflammation and helps the body defend against infections and illness.
What role does selenium play in thyroid health?
Selenium is crucial for the production and activation of thyroid hormones. It helps convert the inactive hormone T4 into the active form T3 and protects the thyroid gland from oxidative damage.
References
- https://ods.od.nih.gov/factsheets/selenium-healthprofessional/
- https://www.southtees.nhs.uk/services/pathology/tests/selenium/
- https://nutritionsource.hsph.harvard.edu/selenium/
- https://wearefeel.com/blogs/learn/best-form-of-selenium-selenite-vs-selenomethionine?srsltid=AfmBOopHKHu7PoKzkoKPRY850sb5Q4BH0M3u8G6b-aQz5NjIM7FNWTeF
- https://www.ncbi.nlm.nih.gov/books/NBK482260/#:~:text=If%20left%20untreated%2C%20selenium%20deficiency,neurological%20symptoms%2C%20and%20musculoskeletal%20abnormalities
- https://www.mayfieldclinic.co.uk/blog/how-selenium-supports-immunity-are-you-getting-enough
- https://www.ejcancer.com/article/S0959-8049(21)00462-7/fulltext
- https://pubmed.ncbi.nlm.nih.gov/31823341/
- https://cyberleninka.ru/article/n/modern-concept-of-biological-identification-of-selenoproteins
- https://pubmed.ncbi.nlm.nih.gov/36172072/
- https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2023.1133000/full
- https://www.webmd.com/a-to-z-guides/supplement-guide-selenium
- https://www.argalys.com/en/blogs/advices/selenium-an-antioxidant-with-many-benefits
- https://www.healthline.com/health/selenium-foods#cottage-cheese
- https://nutritionsource.hsph.harvard.edu/selenium/
