Selenium

Both support immune function and antioxidant defense

Enhanced immune and antioxidant support

✦ Iodine

enhances

Selenium is required for thyroid hormone conversion

Optimal thyroid function — don't supplement iodine without adequate selenium

⟡ Vitamin E

Both support glutathione antioxidant system

Enhanced antioxidant defense

Top studies from 39+ peer-reviewed papers

📚meta-analysisn=9423

Jenkins DJA et al. • The American journal of clinical nutrition (2020)

“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.”

Key Findings:

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.
This trial was registered at https://www.crd.york.ac.uk/PROSPERO/ as CRD42019138268.

📚meta-analysisn=27232

Vinceti M et al. • The Cochrane database of systematic reviews (2018)

“Well-designed and well-conducted RCTs have shown no beneficial effect of selenium supplements in reducing cancer risk (high certainty of evidence).”

Key Findings:

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).
As RCT participants have been overwhelmingly male (88%), we could not assess the potential influence of sex or gender.We included 15 additional observational cohort studies (70 in total; over 2,360,000 participants).

📚meta-analysisn=13254

Hurst R et al. • The American journal of clinical nutrition (2012)

“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.”

Key Findings:

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.
Further research warranted to confirm findings

📚meta-analysisn=869

Huwiler VV et al. • Thyroid : official journal of the American Thyroid Association (2024)

“Indications for lowering TPOAb were found independent of THRT.”

Key Findings:

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.
Adverse effects were comparable between the intervention and control groups (OR 0.89 [CI 0.46 to 1.75]; 16 cohorts; 1339 participants; I2 = 0%).

📚meta-analysisn=8542

Compare with Others Find Based on Your Goals

Liang X et al. • Frontiers in immunology (2024)

“Patients with vitiligo should reduce smoking and alcohol consumption and take appropriate vitamin E, B12, copper, and zinc supplements.”

Key Findings:

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.
However, vitamin C, vitamin D, selenium, iron, and folic acid supplements are unnecessary.

View all 39+ studies

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Selenium

mineral

Selenium (Selenomethionine)

Required for selenoprotein production that regulates thyroid hormones, powers glutathione peroxidase, and strengthens immune defense.

immunitythyroidantioxidantimmuneessential mineral

39+ studies

Evidence

Reviewed 19 days ago

moderate

Safety

100-200mcg

Dose

4- weeks

Time to Effect

Selenomethionine (best absorbed)

Best Form

Mechanisms of Action

🔬

Selenoprotein Synthesis

Required to make crucial antioxidant enzymes

🦋

Thyroid Support

Critical for thyroid hormone metabolism

Biological PathwayBeta

How Selenium works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.

Supplement

Molecular Target

Biological Process

Health Outcome

Strong

Moderate

Emerging

strong

moderate

emerging

Tap node to isolate • Pinch to zoom • Tap edge for research

Recommended Dose

100-200mcg

55mcg400mcg

Optimal Timing

With food

Take with food

Available Forms

Form	Type
💊Selenomethionine (best absorbed)	Recommended
💊Selenium yeast	Alternative
💊Sodium selenite	Alternative

Selenomethionine is the most bioavailable organic form.

Duration

Minimum: 4 weeks

Optimal: weeks

Cycling: Not required

Note: Take with food for better absorption. Do not exceed 400mcg/day from all sources.

🦋

Thyroid Support

Supports healthy thyroid hormone levels

⏱️ 4-8 weeks

60% of users notice thispositive

🛡️

Immune Function

Supports immune cell activity

⏱️ 4-8 weeks

55% of users notice thispositive

ModerateMax safe dose: 400mcg/day (upper tolerable limit)

🟢

Pregnant/nursing

Safe at RDA levels; don't exceed 400mcg

Who Should NOT Take This

Those with adequate/high selenium status
Thyroid conditions (hypothyroidism, hyperthyroidism, Hashimoto's, Graves' disease) — selenium affects thyroid hormone metabolism and may alter thyroid function; consult endocrinologist before use

Drug Interactions

Chemotherapy drugsmoderate

May interact; consult oncologist

Statinsmild

May affect cholesterol-lowering effects

Possible Side Effects

GI upset

milduncommon

Tip: Take with food

Garlic breath (high doses)

milduncommon

Tip: Reduce dose

Hair/nail brittleness (toxicity)

moderateuncommon

Tip: Stop supplementation; indicates excess

Warnings

Narrow therapeutic window — toxicity possible at high doses
Signs of excess: garlic breath, hair loss, nail changes
Test levels before supplementing if uncertain

⟡ Vitamin C

Both support immune function and antioxidant defense

Enhanced immune and antioxidant support

✦ Iodine

enhances

Selenium is required for thyroid hormone conversion

Optimal thyroid function — don't supplement iodine without adequate selenium

⟡ Vitamin E

Both support glutathione antioxidant system

Enhanced antioxidant defense

Top studies from 39+ peer-reviewed papers

📚meta-analysisn=9423

Jenkins DJA et al. • The American journal of clinical nutrition (2020)

“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.”

Key Findings:

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.
This trial was registered at https://www.crd.york.ac.uk/PROSPERO/ as CRD42019138268.

📚meta-analysisn=27232

Vinceti M et al. • The Cochrane database of systematic reviews (2018)

“Well-designed and well-conducted RCTs have shown no beneficial effect of selenium supplements in reducing cancer risk (high certainty of evidence).”

Key Findings:

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).
As RCT participants have been overwhelmingly male (88%), we could not assess the potential influence of sex or gender.We included 15 additional observational cohort studies (70 in total; over 2,360,000 participants).

📚meta-analysisn=13254

Hurst R et al. • The American journal of clinical nutrition (2012)

“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.”

Key Findings:

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.
Further research warranted to confirm findings

📚meta-analysisn=869

Huwiler VV et al. • Thyroid : official journal of the American Thyroid Association (2024)

“Indications for lowering TPOAb were found independent of THRT.”

Key Findings:

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.
Adverse effects were comparable between the intervention and control groups (OR 0.89 [CI 0.46 to 1.75]; 16 cohorts; 1339 participants; I2 = 0%).

📚meta-analysisn=8542

Compare with Others Find Based on Your Goals

Liang X et al. • Frontiers in immunology (2024)

“Patients with vitiligo should reduce smoking and alcohol consumption and take appropriate vitamin E, B12, copper, and zinc supplements.”

Key Findings:

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.
However, vitamin C, vitamin D, selenium, iron, and folic acid supplements are unnecessary.

View all 39+ studies

What would you like to do next?

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Plant compounds with weak estrogenic effects that support menopausal symptoms, bone health, and cardiovascular function.

I9.0

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Essential trace mineral for thyroid hormone production — deficiency is common and affects metabolism, energy, and cognition.

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