Nutrients & foods

Vitamins & minerals

Selenium

Is part of proteins involved in thyroid hormone metabolism and antioxidant defense.

Updated September 17, 2026 · Educational reference

What it does

Is part of proteins involved in thyroid hormone metabolism and antioxidant defense.

Possible deficiency symptoms

Deficiency is uncommon in many settings and cannot be identified from fatigue alone.

Food sources

Seafood; meat; eggs; grains; Brazil nuts, whose selenium content is highly variable.

Supplement forms

Selenomethionine and sodium selenite.

Before taking a supplement

Excess can cause hair and nail changes, gastrointestinal symptoms and nerve problems.

Questions for your visit

Could my diet, medicines, absorption or another condition explain my concern? What evidence would support treatment, and how would we check whether it helps?

Names you may see

Selenium

Sources & perspective

This is an editorial adaptation of the Purser Wellness nutrient reference app. Purser teaching connections are labeled separately from clinical interpretation. Private cases and individual treatment protocols are not reproduced.

Use the public resources below for additional context.

NIH Office of Dietary Supplements: Selenium