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Se6.5
Selenium Research
Probably helps
709 peer-reviewed studies
What the evidence says
Likely helps
Selenium appears to help in 8 of 9 studies with measurable effects — the evidence leans clearly favourable.
Most evidence is from high-quality meta-analyses and randomised trials published 1981–2026 with a typical study size of 869 participants.
Based on 709 studies · 176 meta-analyses · 399 RCTs · 45,218 total participants
Confidence
High confidence
What the studies found
8helped1unclear· 700 more without graded effect data
By outcome
Therapeutic & clinical
Too few graded studies154 studies
Thyroid function
Too few graded studies63 studies
Women's healthLowered pre-eclampsia in a pooled analysis of 3 small trials (439 women). The authors call for more trials before it is confirmed · Ongoing · A PCOS network meta-analysis found better glucose markers. No cited study measured estrogen or cycle symptoms · 4-8 weeks
Too few graded studies62 studies
InflammationOral selenium did not lower CRP in meta-analyses, a small pain benefit in rheumatoid arthritis · 4-8 weeks
Too few graded studies58 studies
Safety profile
Too few graded studies49 studies
Glucose & metabolic
Too few graded studies40 studies
Men's vitalityNeeded to convert T4 to T3. In Hashimoto's it lowers thyroid antibodies, and whether that improves symptoms is not shown · 4-8 weeks · Prostate antioxidant support · 4-12 weeks
Too few graded studies34 studies
Immune supportSelenoproteins are part of immune-cell function. No cited trial measured immune outcomes from supplements · 4-8 weeks
Too few graded studies28 studies
Heart & blood pressure
Too few graded studies27 studies
Cognitive function
Too few graded studies18 studies
Neuroprotection & brain agingLow selenium is seen in Alzheimer's (observational). No trial shows supplements protect the brain · Ongoing
Too few graded studies17 studies
Fertility & reproductive
Too few graded studies13 studies
Cholesterol & lipids
Too few graded studies11 studies
Depression & moodSelenium status correlates with mood; correction improves anxiety and depression · 4-8 weeks
Mostly mechanism / observational9 studies
Skin health
Too few graded studies7 studies
Joint pain & arthritis
Too few graded studies7 studies
Liver health
Too few graded studies1 study
By the numbers
Pulled from 75 studies with measurable effects
Likely real effects
80%
across studies
People studied
45k
typical study: 869 people
Strongest designs
575
176 pooled, 399 randomised
Showed benefit
89%
8/9 studies
How long studies ran
3+ months
2
Populations Studied
General population8
COVID-19 patients3
Hashimoto's thyroiditis patients2
Patients with vitiligo2
Active research area
272 studies in the last 5 years · Latest meta-analysis: 2026
198120032026
1Meta-Analysis2023
In plain English: However, additional investigation is necessary to ascertain whether there is a potential association between these variables.
Li J et al. · Nutrients (2023)
All three methods of MR analysis revealed that Se levels had no effect on OP risk.
In addition, the sensitivity analysis revealed no heterogeneity or pleiotropy, and the significance of the overall effect remained unaffected by single-nucleotide polymorphisms (SNPs), as determined by the leave-one-out analysis, indicating that our findings are relatively reliable.
The results of our study indicate that there is no causal association between Se levels and the risk of OP.
3QUICKI improvementMeta-AnalysisCited 12×n=2,362 · very large study2023
In plain English: Carnitine was relatively effective in reducing body mass, while chromium, Omega-3, and selenium were beneficial for improving glucose metabolism.
Hu X et al. · PeerJ (2023)
The network meta-analysis showed that carnitine, inositol, and probiotics reduced body weight and body mass index (BMI) compared to placebo, and carnitine outperformed the other supplements (SUCRAs: 96.04%, 97.73%, respectively).
Omega-3 lowered fasting blood glucose (FBG) (SUCRAs: 93.53%), and chromium reduced fasting insulin (FINS) (SUCRAs: 72.90%); both were superior to placebo in improving insulin resistance index (HOMA-IR), and chromium was more effective than Omega-3 (SUCRAs: 79.99%).
Selenium was potent in raising the quantitative insulin sensitivity index (QUICKI) (SUCRAs: 87.92%).
4Selenium levels in vitiligo patientsMeta-AnalysisCited 4×n=8,542 · very large study2024
In plain English: Patients with vitiligo should reduce smoking and alcohol consumption and take appropriate vitamin E, B12, copper, and zinc supplements.
Liang X et al. · Frontiers in immunology (2024)
Vitamin C [mean difference (MD), -0.342; 95% confidence interval (CI), -1.090-0.407; p >0.05), folic acid (MD, -1.463; 95% CI, -7.133-4.208; p >0.05), and selenium (MD, 0.350; 95% CI, -0.687-1.387; p >0.05) levels did not differ between the groups.
The serum iron level of the vitiligo group was significantly higher than that of the control group (MD, 1.181; 95% CI, 0.390-1.972; p <0.005).
Patients with vitiligo should reduce smoking and alcohol consumption and take appropriate vitamin E, B12, copper, and zinc supplements.
5TSH levels in patients without THRTMeta-AnalysisCited 61×n=869 · large study2024
In plain English: Indications for lowering TPOAb were found independent of THRT.
Huwiler VV et al. · Thyroid : official journal of the American Thyroid Association (2024)
Noticeable benefit
← WorseNo effectBetter →
We synthesized the results as standardized mean differences (SMD) or odds ratio (OR), assessed risk of bias using the Cochrane RoB 2 tool, and rated the evidence using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.
Our meta-analysis found that selenium supplementation decreased TSH in patients without THRT (SMD -0.21 [confidence interval, CI -0.43 to -0.02]; 7 cohorts, 869 participants; I2 = 0%).
In addition, TPOAb (SMD -0.96 [CI -1.36 to -0.56]; 29 cohorts; 2358 participants; I2 = 90%) and malondialdehyde (MDA; SMD -1.16 [CI -2.29 to -0.02]; 3 cohorts; 248 participants; I2 = 85%) decreased in patients with and without THRT.
6Prostate cancer riskMeta-AnalysisCited 105×n=13,254 · very large study2012
In plain English: The relation between selenium status and decreased prostate cancer risk was examined over a relatively narrow range of selenium status; further studies in low-selenium populations are required.
Hurst R et al. · The American journal of clinical nutrition (2012)
Huge benefit
← WorseNo effectBetter →
Systematic review and dose-response meta-analysis of 12 trials, case-control and cohort studies with 13,254 participants and 5,007 prostate cancer cases, on selenium intake or status.
Prostate cancer risk fell as plasma or serum selenium rose up to 170 ng/mL, and three high-quality studies linked toenail selenium of 0.85 to 0.94 μg/g with lower risk (RR 0.29, 95% CI 0.14 to 0.61).
The link was examined over a narrow range of selenium status, and the authors call for studies in low-selenium populations.
7Preeclampsia incidenceMeta-AnalysisCited 53×n=1,515 · large study2016
In plain English: However, more prospective clinical trials are required to assess the association between selenium supplementation and preeclampsia and to determine the dose, beginning time, and duration of selenium supplementation.
Xu M et al. · Biological trace element research (2016)
Huge benefit
← WorseNo effectBetter →
Likely real
Using a random-effect model, a statistically significant difference in blood selenium concentration of -6.47 μg/l (95 % confidence interval (CI) -11.24 to -1.7, p = 0.008) was seen after comparing the mean difference of observational studies.
Supplementation with selenium significantly reduces the incidence of preeclampsia.
In randomized controlled trials, using a random-effect model, the relative risk for preeclampsia was 0.28 (0.09 to 0.84) for selenium supplementation (p = 0.02).
9Fasting plasma glucose levelsMeta-AnalysisCited 1×n=230 · medium study2025
In plain English: For pregnant women with gestational diabetes mellitus, daily supplementation with 200 µg of selenium may help lower fasting blood glucose levels and the risk of hyperbilirubinemia in the newborn, but it does not significantly affect total cholesterol, triglycerides, low density lipoprotein cholesterol, or high density lipoprotein cholesterol levels.
Sun J et al. · BMC endocrine disorders (2025)
Noticeable benefit
← WorseNo effectBetter →
Likely real
Compared with placebo group, the selenium group did not significantly reduce the level of homeostasis model assessment of insulin resistance(P = 0.20, MD = -0.71, 95%CI: -1.80, 0.37).
Selenium supplementation at 200 µg/d significantly reduced fasting plasma glucose(P = 0.0002, MD = -5.03, 95% CI: -7.70, -2.37) and the incidence of newborn's hyperbilirubinemia((P = 0.0003, MD = 0.09, 95% CI: 0.03, 0.33).
Given the limitations of this study, these conclusions require further validation.
10Selenium levels in skin diseasesMeta-AnalysisCited 29×n=1,315 · large study2020
In plain English: Selenium levels were associated with several skin diseases and the disease severity, and high selenium levels tended to be a protective factor in certain skin diseases.
Lv J et al. · Journal of trace elements in medicine and biology : organ of the Society for Minerals and Trace Elements (GMS) (2020)
Compared with controls, no significant difference in selenium was found in patients with vitiligo (SMD = 0.53, 95% CI: -0.40 to 1.45), alopecia areata (SMD = 0.47, 95% CI: -2.72 and 3.65), or eczema (SMD = 0.12, 95% CI: -0.24 to 0.48).
A lower selenium level was found in patients with psoriasis (SMD = -0.62, 95% CI: -1.15 to -0.10), acne vulgaris (SMD = -1.02, 95% CI: -1.45 to -0.60), chloric acne (SMD = -2.35, 95% CI: -3.15 to -1.55), and atopic dermatitis (SMD = -2.62, 95% CI: -3.00 to -2.24).
As for disease severity, severe patients had a higher selenium level than mild patients in psoriasis (SMD = 0.72, 95% CI: 0.07-1.38), but no difference was found in vitiligo (SMD = -0.26, 95% CI: -2.38 to 1.85) and alopecia areata (SMD = 0.46, 95% CI: -0.34 to 1.26).