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Se9.0
Selenium Research
Likely helpsModerate safety
133 peer-reviewed studies
What the evidence says
Likely helps
Selenium appears to help in 19 of 23 studies with measurable effects — the evidence leans clearly favourable.
Most evidence is from high-quality meta-analyses and randomised trials published 2008–2026 with a typical study size of 230 participants.
Based on 133 studies · 38 meta-analyses · 13 RCTs · 211,631 total participants
Confidence
High
What the studies found
19helped3unclear1didn't help· 110 more without graded effect data
By outcome
Thyroid function
Likely helps22 studies
Therapeutic & clinical
Likely helps20 studies
Immune supportSupports immune cell function · 4-8 weeks
Mostly mechanism / observational19 studies
InflammationSelenoproteins (GPx) reduce oxidative stress and inflammation · 4-8 weeks
Mostly mechanism / observational14 studies
Safety profile
Mostly mechanism / observational12 studies
Women's healthSupports healthy estrogen metabolism and hormonal equilibrium · 4-8 weeks · Provides essential nutrients for healthy pregnancy · Ongoing
Likely helps11 studies
Cognitive function
Mostly mechanism / observational9 studies
Glucose & metabolic
Probably helps8 studies
Heart & blood pressure
Mostly mechanism / observational7 studies
Depression & moodSelenium status correlates with mood; correction improves anxiety and depression · 4-8 weeks
Mostly mechanism / observational6 studies
Neuroprotection & brain agingSelenoprotein-mediated antioxidant defence in CNS · Ongoing
Mostly mechanism / observational6 studies
Cholesterol & lipids
Mostly mechanism / observational5 studies
Skin health
Mostly mechanism / observational3 studies
Fertility & reproductiveMay support reproductive health and fertility markers · 4-12 weeks
Too few graded studies2 studies
Men's vitalityEssential for thyroid hormone conversion (T4 to T3) · 4-8 weeks · Prostate antioxidant support · 4-12 weeks
Too few graded studies2 studies
Liver health
Too few graded studies1 study
Joint pain & arthritis
Too few graded studies1 study
By the numbers
Pulled from 54 studies with measurable effects
Likely real effects
82%
across studies
People studied
212k
typical study: 230 people
Strongest designs
51
38 pooled, 13 randomised
Showed benefit
83%
19/23 studies
How long studies ran
1–3 months
1
3+ months
1
Populations Studied
General population6
Hashimoto's thyroiditis patients3
Pregnant women2
Alzheimer's disease patients2
Active research area
116 studies in the last 5 years · Latest meta-analysis: 2025
200820172026
1Meta-Analysisn=4,162 · very large study2023
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.
3Body weight reductionMeta-AnalysisCited 10×n=2,362 · very large study2023
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%).
4Serum iron levelsMeta-AnalysisCited 3×n=8,542 · very large study2024
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)
Noticeable benefit
← WorseNo effectBetter →
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 51×n=869 · large study2024
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.
6CVD mortality with selenium-containing antioxidant mixturesMeta-AnalysisCited 104×n=9,423 · very large study2020
The addition of selenium should be considered for supplements containing antioxidant mixtures if they are to be associated with CVD and all-cause mortality risk reduction.
Jenkins DJA et al. · The American journal of clinical nutrition (2020)
Noticeable benefit
← WorseNo effectBetter →
Likely real
However, a decreased risk with antioxidant mixtures was seen for CVD mortality when selenium was part of the mix (RR: 0.77; 95% CI: 0.62, 0.97; P = 0.02), with no association when selenium was absent.
Similarly, when selenium was part of the antioxidant mixture, a decreased risk was seen for all-cause mortality (RR: 0.90; 95% CI: 0.82, 0.98; P = 0.02) as opposed to an increased risk when selenium was absent (RR: 1.09; 95% CI: 1.04, 1.13; P = 0.0002).
The addition of selenium should be considered for supplements containing antioxidant mixtures if they are to be associated with CVD and all-cause mortality risk reduction.
7Any cancer incidenceMeta-AnalysisCited 264×n=27,232 · very large study2018
Well-designed and well-conducted RCTs have shown no beneficial effect of selenium supplements in reducing cancer risk (high certainty of evidence).
Vinceti M et al. · The Cochrane database of systematic reviews (2018)
No clear effect
← WorseNo effectBetter →
For analyses of RCTs with low risk of bias, the summary risk ratio (RR) for any cancer incidence was 1.01 (95% confidence interval (CI) 0.93 to 1.10; 3 studies, 19,475 participants; high-certainty evidence).
The RR for estimated cancer mortality was 1.02 (95% CI 0.80 to 1.30; 1 study, 17,444 participants).
Selenium supplementation did not reduce overall cancer incidence (RR 0.99, 95% CI 0.86 to 1.14; 5 studies, 21,860 participants) nor mortality (RR 0.81, 95% CI 0.49 to 1.32; 2 studies, 18,698 participants).
8Prostate cancer riskMeta-AnalysisCited 104×n=13,254 · very large study2012
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 →
Three high-quality studies included in the meta-analysis of toenail selenium and cancer risk indicated a reduction in prostate cancer risk (estimated RR: 0.29; 95% CI: 0.14, 0.61) with a toenail selenium concentration between 0.85 and 0.94 μg/g.
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.
9Selenium levels in skin diseasesMeta-AnalysisCited 28×n=1,315 · large study2020
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)
Large benefit
← WorseNo effectBetter →
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).
10Preeclampsia incidenceMeta-AnalysisCited 52×n=1,515 · large study2016
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).
11Fasting plasma glucose levelsMeta-Analysisn=230 · medium study2025
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.
13Serum micronutrient levels in vitiligoMeta-AnalysisCited 3×n=41 · small study2024
This meta-analysis examined the effects of Copper.
Anam K et al. · Scientific reports (2024)
Publication bias was not found for the studies analysed.
This study analyses the association of serum micronutrient levels and vitiligo among patients and controls from published research along with sub-group analysis specific to Asian populations using a meta-analysis.
Low serum levels of Zinc and copper and high selenium levels are associated with Vitiligo.
14Trace elements in Alzheimer dementiaMeta-AnalysisCited 39×n=73 · small study2023
In a further meta-analysis, standardized mean differences (SMDs) of 13 elements were calculated to evaluate their altered in AD patients, including copper, iron, zinc, selenium, manganese, lead, al...
Li K et al. · Environmental pollution (Barking, Essex : 1987) (2023)
Noticeable benefit
← WorseNo effectBetter →
In a further meta-analysis, standardized mean differences (SMDs) of 13 elements were calculated to evaluate their altered in AD patients, including copper, iron, zinc, selenium, manganese, lead, aluminum, cadmium, chromium, arsenic, mercury, cobalt, and manganese.
We identified four trace elements-copper (serum), iron (plasma), zinc (hair), and selenium (plasma)-altered in AD patients, with SMDs of 0.37 (95% confidence interval [CI]: 0.10, 0.65), -0.68 (95% CI: -1.34, -0.02), -0.35 (95% CI: -0.62, -0.08), and -0.61 (95% CI: -0.97, -0.25), respectively.
Finally, we formed a database of various trace element levels in AD patients and healthy controls.
Roldán-Bretón NR et al. · Journal of nutritional science (2023)
Meta-analysis was conducted to mean difference (MD) with a 95 % confidence interval (CI), and heterogeneity was tested by I2 with random factors with a MD between selenium levels, mortality, morbidity and healthy subjects with a P-value of 0⋅05.
In conclusion, the patients with active SARS-CoV-2 infection had lower selenium levels than the healthy population.
17Micronutrient levels in diabetic foot ulcerMeta-AnalysisCited 16×2023
This review provides evidence that micronutrient levels significantly differ in DFU patients, suggesting an association between micronutrient status and risk of DFU.
Kurian SJ et al. · Frontiers in endocrinology (2023)
Noticeable benefit
← WorseNo effectBetter →
DFU, compared to healthy controls (HC) had significantly lower vitamin D (MD: -10.82 14 ng/ml, 95% CI: -20.47, -1.16), magnesium (MD: -0.45 mg/dL, 95% CI: -0.78, -0.12) and selenium (MD: -0.33 µmol/L, 95% CI: -0.34, -0.32) levels.
DFU, compared to DM patients without DFU, had significantly lower vitamin D (MD: -5.41 ng/ml, 95% CI: -8.06, -2.76), and magnesium (MD: -0.20 mg/dL, 95% CI: -0.25, -0.15) levels.
The overall analysis showed lower levels of vitamin D [15.55ng/ml (95% CI:13.44, 17.65)], vitamin C [4.99µmol/L (95% CI:3.16, 6.83)], magnesium [1.53mg/dL (95% CI:1.28, 1.78)] and selenium [0.54µmol/L (95% CI:0.45, 0.64)].
Although some of the data suggested beneficial effects of selenium supplementation on immune function, the overall picture appears to be inconsistent and heterogeneous due to differences in trial duration and interventions, plus evidence of null and even detrimental effects.
Filippini T et al. · The American journal of clinical nutrition (2023)
Although some of the data suggested beneficial effects of selenium supplementation on immune function, the overall picture appears to be inconsistent and heterogeneous due to differences in trial duration and interventions, plus evidence of null and even detrimental effects.
This trial was registered at PROSPERO (CRD42022312280).
19Selenium concentrations in AD patientsMeta-AnalysisCited 31×2023
Generally, this meta-analysis indicated that AD patients are strongly associated with lower selenium concentrations compared with healthy people, which may provide a clinical reference in the future.
Zhou J et al. · Nutrients (2023)
Noticeable benefit
← WorseNo effectBetter →
Likely real
A statistically significant relationship was only found for AD patients (SMD = -0.41, 95% CI (-0.64, -0.17), p < 0.001), especially for erythrocytes.
Generally, this meta-analysis indicated that AD patients are strongly associated with lower selenium concentrations compared with healthy people, which may provide a clinical reference in the future.
However, more studies are urgently needed for further study and treatment of neurodegenerative diseases.