What is selenium?


Exploring Selenium: An Essential Trace Mineral

Selenium is an important trace mineral that is essential for various biological processes in the human body. It plays a crucial role as a cofactor for several enzymes and is involved in antioxidant defense, thyroid hormone metabolism, DNA synthesis, and immune function. In this article, we will delve into what selenium is, its functions, dietary sources, and the importance of maintaining optimal selenium levels.

1. What is Selenium?

Selenium is a mineral that is naturally found in the soil and can be absorbed by plants. It exists in several chemical forms, with selenomethionine and selenocysteine being the most common organic forms found in food sources. These forms of selenium are bioavailable and easily absorbed by the body.

2. Functions of Selenium

Selenium is involved in various physiological processes:

  • Antioxidant activity: Selenium is a component of antioxidant enzymes, such as glutathione peroxidases, which help neutralize harmful free radicals and protect cells from oxidative damage.
  • Thyroid hormone metabolism: Selenium is necessary for the conversion of thyroid hormones, specifically the conversion of thyroxine (T4) to triiodothyronine (T3), which is the active form of the hormone.
  • Immune function: Selenium plays a role in supporting a healthy immune system by influencing the function of immune cells and contributing to the body’s defense against infections and diseases.
  • DNA synthesis and repair: Selenium is involved in DNA synthesis and repair processes, ensuring the integrity and stability of the genetic material.
  • Reproduction: Selenium is important for male and female reproductive health and is involved in sperm production, fertility, and pregnancy outcomes.

3. Dietary Sources of Selenium

Selenium can be obtained through a variety of dietary sources:

  • Seafood: Fish and shellfish, such as tuna, sardines, shrimp, and oysters, are excellent sources of selenium.
  • Meat and poultry: Organ meats, lean meats, and poultry are good sources of selenium.
  • Plant-based sources: Nuts and seeds, such as Brazil nuts and sunflower seeds, are rich in selenium. Additionally, grains, legumes, and vegetables can contribute to selenium intake, although the content may vary depending on the soil conditions.
  • Selenium supplements: In some cases, selenium supplements may be recommended to meet specific dietary needs, but it is important to consult with a healthcare professional before starting any supplementation regimen.

4. Maintaining Optimal Selenium Levels

Maintaining optimal selenium levels is crucial for overall health and well-being. While selenium deficiency is rare in many parts of the world, it can occur in areas where soil selenium content is low. Conversely, excessive selenium intake can lead to toxicity and have negative health effects.

The recommended dietary allowance (RDA) for selenium varies based on age, sex, and life stage. It is important to consume selenium within the recommended range to avoid deficiencies or excesses.

The Bottom Line


elenium is an essential trace mineral that plays a vital role in various physiological processes, including antioxidant defense, thyroid hormone metabolism, immune function, and DNA synthesis. It can be obtained through a balanced diet that includes seafood, meat, poultry, nuts, seeds, and plant-based sources. Maintaining optimal selenium levels is important for overall health, and it is advisable to consult with a healthcare professional to determine the appropriate selenium intake based on individual needs.