Selenium

Also known as selenomethionine, sodium selenite, selenuim.

Last reviewed October 9, 2026 · Jump to references

What is Selenium?

In plain words

Selenium is a mineral the body needs in small amounts. The body uses it to make proteins that help protect cells from damage and control thyroid hormones. Researchers study its roles in thyroid health, immune function, and correcting low selenium levels. Too much selenium can be toxic, and extra selenium has not shown clear benefits for people who already get enough.

Technical definition

Selenium is an essential trace element supplied in organic forms such as selenomethionine and inorganic forms such as sodium selenite. It is incorporated as selenocysteine into selenoproteins, including glutathione peroxidases and thyroid hormone deiodinases, which support peroxide metabolism and thyroid hormone regulation rather than acting through a single receptor. In the United States, selenium is available in dietary supplements, which are not FDA-approved for safety and effectiveness before marketing.

Educational information only. This page does not provide medical advice or determine whether a supplement is appropriate for you. Review supplements with a qualified healthcare professional, especially if you take medication, are pregnant, have surgery scheduled, or have a chronic medical condition.

Evidence by use

Each use is rated on its own. There is no single overall effectiveness score.