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Trace mineral

Selenium

Selenoproteins (antioxidant glutathione peroxidase), thyroid hormone metabolism, immunity

Essential nutrient

Reference intakes (RDA or AI) are set by the National Academies of Sciences, Engineering, and Medicine. Deficiency thresholds come from clinical and WHO guidance.

At a glance

Women, 19-50
55 mcg (60 mcg pregnancy, 70 mcg lactation)
Men, 19-50
55 mcg
Upper limit (adults)
400 mcg/day
How common is deficiency?
Uncommon in the US; COMMON in selenium-poor soil regions (parts of China, Eastern Europe, Africa)

Food sources

Animal sources
Brazil nuts are plant; animal: tuna, halibut, sardines, shrimp, beef, turkey, eggs, organ meats
Plant sources
Brazil nuts (very high - 1-2 daily is enough), sunflower seeds, brown rice, mushrooms, whole grains (depends on soil)

Deficiency and testing

Signs of deficiency
Keshan disease (cardiomyopathy), Kashin-Beck disease (joint), hypothyroidism, weakened immunity, fatigue, brain fog, hair loss, male infertility
Who is at higher risk
Residents of low-selenium regions, HIV, long-term parenteral nutrition, severe GI disease, dialysis
How it is tested
Plasma/serum selenium; glutathione peroxidase 3 activity; selenoprotein P (best functional marker); toenail selenium (long-term)
Cut-offs
Plasma selenium <70 mcg/L (<0.9 umol/L) = low; <45 mcg/L = deficiency risk

Symptoms are not specific. Only a clinician with the right tests can tell whether you are deficient.

Supplement forms

Common forms
selenomethionine, sodium selenite, sodium selenate, selenium-enriched yeast, Brazil nuts.
More effective
selenomethionine and selenium yeast (well absorbed, stored in tissue proteins, raise blood levels steadily); sodium selenite is also effective and absorbed, but is less retained; 1-2 Brazil nuts a day can meet the RDA.
Less effective
Brazil nuts as a precise dose (content varies widely by origin); supplements above 400 mcg/day (selenosis: hair and nail loss, garlic breath); routine use in selenium-replete people (no proven benefit and possible higher diabetes risk).

Safety, interactions and halal notes

Safety and interactions
Upper limit for adults: 400 mcg/day. Going above the upper limit over time can cause harm, so check labels and talk to a clinician before high-dose supplements.
Halal note
The nutrient itself is not a halal question. For supplements, check the delivery form: gelatin (pork or non-halal bovine), capsule shells, glycerin, and alcohol-based carriers need halal certification. Ask for the halal certificate, not just a label claim. This is general guidance, not a certification.

Frequently asked questions

How much Selenium do adults need per day?

Women 19-50: 55 mcg (60 mcg pregnancy, 70 mcg lactation). Men 19-50: 55 mcg. Upper limit: 400 mcg/day. Needs change with age, pregnancy and health conditions.

What are the signs of Selenium deficiency?

Keshan disease (cardiomyopathy), Kashin-Beck disease (joint), hypothyroidism, weakened immunity, fatigue, brain fog, hair loss, male infertility. These signs are not specific, so only a clinician with the right tests can confirm a deficiency.

What are the best food sources of Selenium?

Animal sources: Brazil nuts are plant; animal: tuna, halibut, sardines, shrimp, beef, turkey, eggs, organ meats. Plant sources: Brazil nuts (very high - 1-2 daily is enough), sunflower seeds, brown rice, mushrooms, whole grains (depends on soil).

Which form of Selenium supplement is best?

selenomethionine and selenium yeast (well absorbed, stored in tissue proteins, raise blood levels steadily); sodium selenite is also effective and absorbed, but is less retained; 1-2 Brazil nuts a day can meet the RDA.

Sources

  1. NIH Office of Dietary Supplements fact sheet

← Back to the full nutrient guide

This page is for education only and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. Supplements are not intended to diagnose, treat, cure or prevent any disease. Talk to a qualified clinician before starting a supplement, especially if you are pregnant, breastfeeding, take medicine or have a medical condition. Daily needs are US reference intakes for adults 19-50.

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