Supplement evidence

019 / 575Mineral

Selenium

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The short answer

Preventing or treating deficiency in low-selenium settings or specific medical conditions.

Evidence and scope: Established for an indicated use
This status does not grade the ingredient for every goal, outcome, or person.
Important limitation: Supplementation has not established cancer prevention or lifespan benefit in replete adults.
Before deciding: The safety margin is narrow; excess can cause hair and nail loss, neurologic symptoms, and garlic breath.

01 / PRACTICAL GUIDE

Dose, absorption, and combinations

These are indication-specific reference or studied ranges—not a personalized prescription. Start with the objective, then check the form, label, medicines, and health conditions.

Reference range by objective

Meeting usual needs55 mcg/day

Reference or studied range—not a personalized prescription. The product label or a clinician may specify a different dose.

Dose source ↗

Confirmed deficiencyOnly supplement a demonstrated low-intake or clinical context

Reference or studied range—not a personalized prescription. The product label or a clinician may specify a different dose.

Dose source ↗

More is not automatically better. A clinician or product label may specify a different amount.

Absorption / solubilityWater-soluble

Water-soluble or readily water-dispersible. This does not mean excess is always harmless.

How it is commonly taken

May be taken with food.

Do not combine casually

Avoid stacking products near the 400 mcg/day U.S. upper limit; excess causes hair, nail, nerve, and GI toxicity.

Dose and use source ↗

Dose and use links lead to primary or official source material. Search links are discovery tools, not proof that every returned paper applies.

02 / EVIDENCE

What the research says

We keep supportive, mixed, negative, safety, and contextual findings together. The headline never replaces the underlying papers.

4research papers in this ledger

46unique primary studies represented

27,723unique participants represented

These are audited counts for this JIVANA collection, not search-result totals. Participants are counted once when multiple papers use the same cohort; review papers are not added again to participant totals.

Open the research timelineResearch timeline

Entries are ordered by publication year. A study period appears only when the source reports it.

2024

Mixed or qualifiedPMID 38243784 · CRD42022308377

Selenium Supplementation in Patients with Hashimoto Thyroiditis

Selenium modestly lowered TSH in untreated patients and reduced thyroid-peroxidase antibodies, but did not improve most thyroid hormones or thyroid volume; antibody changes are not proof of better symptoms or disease progression.

Published: 202435 primary studies represented

Study design and methods

Design: Systematic review and meta-analysis of 35 randomized studies
Population: People with Hashimoto thyroiditis, with or without thyroid-hormone replacement
Intervention: Selenium supplementation versus control
Outcome: Thyroid hormones, antibodies, imaging, patient-reported outcomes, and adverse effects

Funding or conflict note: The authors declared no conflicts. Outcome-specific participant counts varied, so no single participant total is inferred.

Open research record ↗

2018

Does not support the tested claimPMID 29376219

Selenium for preventing cancer

High-certainty randomized evidence found no cancer-prevention benefit. Trials raised concerns about diabetes, alopecia, dermatitis, and high-grade prostate cancer in people with high baseline selenium.

Published: 2018n=27,232 participants10 primary studies represented

Study design and methods

Design: Cochrane systematic review including 10 randomized trials
Population: 27,232 adults randomized to selenium or placebo
Intervention: Selenium supplements versus placebo
Outcome: Overall and site-specific cancer incidence and mortality; adverse effects

Open research record ↗

2018

Safety signalPMID 29974401

Selenium exposure and the risk of type 2 diabetes

Across randomized trials, selenium supplementation increased diabetes risk by about 11%. Observational results also rose with exposure but cannot establish causation.

Published: 20185 primary studies represented

Study design and methods

Design: Systematic review and meta-analysis including five randomized trials
Population: Adults in selenium-supplementation trials plus observational cohorts
Intervention: Selenium 200 μg/day versus placebo in the randomized evidence
Outcome: Incident type 2 diabetes

Funding or conflict note: The randomized trials overlap the cancer-prevention evidence set and are excluded from aggregate totals.

Open research record ↗

2018

Safety signalPMID 29454039

Effect of long-term selenium supplementation on mortality

The 300 μg/day group had higher mortality over the full follow-up; lower doses did not show a durable mortality benefit. The mortality analysis was secondary and the trial was small.

Published: 2018Duration: 5 years of treatment and 10 further years of mortality follow-upn=491 participants

Study design and methods

Design: Randomized, double-blind, placebo-controlled multiple-dose trial
Population: 491 Danish adults aged 60–74 with moderately low selenium status
Intervention: Selenium yeast 100, 200, or 300 μg/day versus placebo
Outcome: All-cause mortality

Open research record ↗

Unscreened discovery appendix—not evidence414 candidate publicationsSearch run: Aug 21, 2026

Complete for the displayed PubMed query at the search timestamp—not for all databases or every possible synonym. Candidates can be irrelevant, duplicate the same study, or report negative findings. They are never summed as evidence or participants until screened.

03 / SOURCES

Start with the source material

Official evidence overviewNIH Office of Dietary Supplements Live PubMed discovery searchNational Library of Medicine

The live search is for discovery only. Search-result counts change and are not included in the audited totals above.

Recent PubMed discovery recordsDirect links to the first 12 records returned by the reproducible search. These are discovery candidates—not reviewed summaries or a count of supportive findings.

04 / EXPERT CONTEXT

Expert context—not evidence

Expert positions are dated context—not scientific evidence. They never raise the evidence status or become consensus by repetition.

No direct, source-verified endorsement is currently recorded. Research authorship or discussion alone is not treated as endorsement.