Selenium for Cardiovascular Disease

Verdict: Selenium does not prevent cardiovascular disease

For people who are not selenium-deficient, selenium supplements do not lower the risk of heart attack, stroke, or cardiovascular death. The evidence runs against any cardioprotective claim, and high doses carry their own harms.

D 🔴 D Counter-Evidence Counter-Evidence

🔬Why this grade7-layer evidence engine

This earns a Counter-Evidence grade because the highest-quality evidence is consistently negative on hard cardiovascular outcomes. A Cochrane systematic review of 12 trials (PMID 23440843, n=19,715) found no effect on all-cause mortality (RR 0.97), cardiovascular mortality (RR 0.97), or total CVD events (RR 1.03). The largest single trial, SELECT (PMID 19066370, n=35,533), showed no cardioprotective signal, and the pooled randomized data in an earlier meta-analysis (PMID 17023702) were also non-significant (RR 0.89), with its authors explicitly advising against selenium for CVD prevention.

Short-term lipid changes do not rescue the picture. A six-month trial (PMID 21576533) reported a small dose-dependent drop in total cholesterol, but a five-year trial in older adults (PMID 26420334) found no lasting effect on the lipid profile. These are surrogate markers that did not translate into fewer cardiovascular events.

There is also a real safety concern: a secondary analysis of the NPC trial (PMID 17620655) found selenium raised type 2 diabetes incidence (HR 1.55), a major cardiovascular risk factor, especially in people who already had ample selenium. Regulators and clinicians agree, with Harvard Health stating trials have not shown selenium reduces CVD or cardiac death, the American Heart Association advising against antioxidant supplements, and WHO endorsing selenium only for Keshan-disease prevention in genuinely deficient regions, not general heart protection.

⚖️

Scoring transparency

All scores computed by a 7-layer evidence engine — fully auditable

Raw score 0.22

← counter-evidence / ineffectiveeffective / strong evidence →

Final grade

D · Counter-Evidence

Confidence

78%

Broadly consistent

Evidence level

Cochrane high-quality SR/MA

How strongly each layer supports this effect

lower = less supportive

L2 PubMedPrimary literature

0.20

L3 MechanismPlausibility

0.20

L5 Clinical bodiesAuthoritative stance

0.21

L11 AI re-checkIndependent read

0.30

L1 ExamineGlobal benchmark

0.50

Against Mixed Supports

▸View the full decision path (audit trail)

compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.217
tier_from_score — 依分數區間映射至 tier letter
apply_hec_rules — 高品質 SR/MA 顯示 negative 主導 (2 negative > 0 positive)，下層 RCT 不能推翻
apply_hec_override — HEC-1 高階證據 negative — 強制由 U 改為 D
tier_strict_requirement_check — Tier 條件達標，未降階
detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
decide_status — 依 tier + dispute 結果決定 status

📄PubMed studies (6)L2 · primary research & systematic reviews

Selenium supplementation for the primary prevention of cardiovascular disease

PMID: 23440843 2013 Cochrane SR n = 19,715

Finding: No significant effect on all-cause mortality (RR 0.97, 95% CI 0.88-1.08), CVD mortality (RR 0.97, 95% CI 0.79-1.20), non-fatal CVD (RR 0.96, 95% CI 0.89-1.04), or all CVD events (RR 1.03, 95% CI 0.95-1.11). Significant excess of alopecia and dermatitis with Se.

🟢 High quality Academic Effect size: [object Object]

View on PubMed

Selenium and coronary heart disease: a meta-analysis

PMID: 17023702 2006 統合分析

Finding: Observational cohorts: pooled RR 0.85 (95% CI 0.74-0.99) for highest vs lowest Se; case-control RR 0.43 (95% CI 0.29-0.66). Pooled RCTs: RR 0.89 (95% CI 0.68-1.17) — not significant. Authors concluded Se should NOT be recommended for CVD prevention.

🟢 High quality Academic Effect size: [object Object]

View on PubMed

Effect of supplementation with high-selenium yeast on plasma lipids: a randomized trial

PMID: 21576533 2011 RCT (double-blind) n = 501

Finding: Modest dose-dependent reduction in total cholesterol at 100 mcg (-0.22 mmol/L, p=0.02) and 200 mcg (-0.25 mmol/L, p=0.008); 300 mcg increased HDL 0.06 mmol/L (p=0.045). Total/HDL ratio decreased progressively with dose (p=0.01). Surrogate lipid markers only — no hard CV endpoints.

Academic Effect size: [object Object]

View on PubMed

Randomised controlled trial of the effect of long-term selenium supplementation on plasma cholesterol in an elderly Danish population

PMID: 26420334 2015 RCT (double-blind) n = 491

Finding: Total cholesterol decreased in both intervention and placebo groups; small and non-significant between-group differences across all lipid measures at 6 months and 5 years. Long-term Se did not significantly alter lipid profile.

🟢 High quality Academic

View on PubMed

Effects of long-term selenium supplementation on the incidence of type 2 diabetes: a randomized trial (NPC trial secondary analysis)

PMID: 17620655 2007 RCT (double-blind) n = 1,202

Finding: Selenium INCREASED T2DM incidence: 12.6 vs 8.4 cases per 1000 person-yr; HR 1.55 (95% CI 1.03-2.33); exposure-response gradient with highest baseline Se tertile at greatest risk. Harm signal for a major CV risk factor.

🟢 High quality Government Effect size: [object Object]

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Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT)

PMID: 19066370 2009 RCT (double-blind) n = 35,533

Finding: Selenium did not reduce prostate cancer (primary endpoint null); no signal of cardiovascular benefit reported. Trend toward increased T2DM risk with Se (RR 1.07; not statistically significant in primary report). No cardioprotective effect demonstrated in the largest Se RCT to date.

🟢 High quality Government Effect size: [object Object]

View on PubMed

🏛️Regulatory & authoritative positionsL4/L5 · FDA / EMA / NIH ODS / Cochrane / Mayo …

L4a US FDA

Cautious

Selenium may reduce the risk of certain cancers. Some scientific evidence suggests that consumption of selenium may reduce the risk of certain forms of cancer. However, FDA has determined that this evidence is limited and not conclusive. source↗

L4b EU EFSA

Supportive

Selenium contributes to normal thyroid function; contributes to the normal function of the immune system; contributes to the protection of cells from oxidative stress; contributes to normal spermatogenesis; contributes to the maintenance of normal hair; contributes to the maintenance of normal nails. source↗

L4c UK NHS

Cautious

75μg a day for men (19 to 64 years); 60μg a day for women (19 to 64 years). You should be able to get all the selenium you need by eating a varied and balanced diet that includes meat, fish or nuts. Taking 350μg or less a day of selenium supplements is unlikely to cause any harm. Too much selenium causes selenosis, a condition that, in its mildest form, can lead to loss of hair and nails. source↗

L4d TW TFDA / 衛福部

Supportive

形態屬膠囊狀、錠狀且標示有每日食用限量之食品，在每日食用量中，其硒之總含量不得高於200 μg。限於補充食品中不足之營養素時使用。 source↗

L4e WHO

Supportive

Prophylaxis consisting of oral administration of selenium 3 months before the periods of highest anticipated risk is highly effective. Once the disease is established, selenium is of little or no therapeutic value. source↗

L5a NIH Office of Dietary Supplements

Cautious

Selenium is a trace element that is naturally present in many foods, added to others, and available as a dietary supplement. Selenium, which is nutritionally essential for humans, is a constituent of more than two dozen selenoproteins that play critical roles in reproduction, thyroid hormone metabolism, DNA synthesis, and protection from oxidative damage and infection. source↗

L5b Mayo Clinic

Against

L5c Cleveland Clinic

Cautious

Very high selenium consumption can lead to selenium toxicity, which is associated with severe issues, like: breathing problems, tremors, kidney failure, heart attack, heart failure source↗

L5d Harvard Health

Against

Clinical trials have not found that selenium supplements reduce the risk of CVD or cardiac death; however these trials were small and included people who were not likely selenium deficient at the start of the study. source↗

L5e Specialty Society (condition-mapped)

Against

Avoid antioxidant vitamin supplements such as A, C and E. Scientific evidence does not support their benefit. source↗

✓PMID 100% verifiedevery citation checked via NCBI Entrez

🔬6 PubMed studiesindependently re-checked by multiple sub-agents

engine_version: v1.0 claim_id: CLM-COND-cardiovascular-disease-INT-selenium-001 繁體中文版 →