Selenium for Immune Function
Selenium supports immune function where status is low, and deficiency is associated with worse viral outcomes - but supplementing replete people shows no benefit.
Overview
Verdict
How It Works
Dosing & Protocol
Typical dose
- Recommended dose
- 55-200 mcg/day of selenium with food; benefit is confined to correcting deficiency, and 400 mcg/day is the upper limit
- Expected timeframe
- 8-12 weeks
Protocol
- form
- Selenomethionine or selenium-enriched yeast; sodium selenite in many clinical trials
- duration
- 8-12 weeks
- co factor
- Take with food. Evidence is mixed. Selenium is genuinely required for immune function: selenoproteins are involved in T-cell proliferation, neutrophil function and antibody production, and deficiency impairs immunity and has been linked to increased virulence of viral infections including a classic body of work on Keshan disease and coxsackievirus. Correcting deficiency improves immune measures. Supplementing selenium-replete people has not shown consistent immune benefit, and some trials have raised concerns - excess selenium can be immunosuppressive, and the relationship follows an inverted U-curve where both deficiency and excess impair function.
- titration
- Do not exceed 200 mcg/day from supplements without medical supervision; 400 mcg/day is the tolerable upper limit from all sources
- starting dose
- 55-100 mcg/day with food, ideally after checking dietary intake
Evidence
What the studies say
Selenium supplementation and immune function including natural killer cell activity: a randomized controlled trial
Hawkes WC, Kelley DS, Taylor PC
Selenium produced no consistent improvement in natural killer cell activity in already replete men
Selenium and immune function: a systematic review and meta-analysis of experimental human studies
Filippini T
Although some of the data suggested beneficial effects of selenium supplementation on immune function, the overall picture appears to be inconsistent.
Safety
Caveats
The inverted U-curve is the key point: more is not better, and excess selenium is itself immunosuppressive as well as raising diabetes risk. The SELECT trial found increased type 2 diabetes with 200 mcg/day, chronic excess causes selenosis with hair loss, brittle nails, garlic breath, rash and peripheral neuropathy, and acute overdose can be fatal. The tolerable upper intake level is 400 mcg/day from all sources - Brazil nuts contain up to 90 mcg each, so a small handful daily can exceed it, and stacking a multivitamin with a separate selenium product easily doubles intake. Selenium status is generally adequate in North America and low in parts of Europe, China and New Zealand. For immune function, the interventions with real evidence are vaccination, sleep, physical activity, not smoking, and correcting genuine deficiencies of vitamin D, zinc, iron and protein. Recurrent, severe or unusual infections warrant medical assessment for immunodeficiency, diabetes or HIV. In pregnancy the RDA is 60 mcg/day and the upper limit applies.
Less likely to help if
Medical Disclaimer
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Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.