Nutrients
Selenium
Se
Included in Complete.
Compare membershipsYour thyroid relies on this trace mineral.
Selenium is a trace mineral your body builds into proteins called selenoproteins. These help activate thyroid hormones, support DNA production and reproduction, and protect cells from oxidative damage and infection.
Soil and food choices both shape your selenium intake.
The selenium in plant foods depends on how much is in the soil where they grow, which varies widely by region. Seafood, meat, poultry, eggs, and grains are reliable sources. Because food travels widely, local soil matters less in countries like Canada.
Brazil nuts are unusually rich in selenium, and the amount varies a lot from nut to nut. Eating them often, or taking supplements, can push intake too high. A blood selenium result mainly reflects your recent intake.
Some selenium is essential. More isn't always better.
Questions
What does a low selenium result mean?
Low selenium is uncommon. When it happens, it's more often linked to conditions or surgeries that affect how the gut absorbs nutrients. Your clinician will look at it alongside your diet, thyroid results, and health history.
What about a high result?
A higher result usually reflects recent intake, often from supplements or frequent Brazil nuts. Very high intake over time can cause hair loss, brittle nails, nausea, and fatigue. It's worth reviewing any supplements with a clinician.