Selenium for Type 2 Diabetes
Verdict: Counter-Evidence
Across 7 PubMed studies, the evidence for Selenium in Type 2 Diabetes grades Tier D — counter-evidence. High-quality evidence indicates it is not effective (or is harmful) for this use.
D 🔴 D Counter-Evidence Counter-Evidence
Why this grade7-layer evidence engine
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Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditableRaw score 0.27
D
C
B
A
S
← counter-evidence / ineffectiveeffective / strong evidence →
Final grade
D · Counter-Evidence
Confidence
76%
Broadly consistent
Evidence level
E1
Cochrane high-quality SR/MA
▸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 = 0.272
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 內部嚴重矛盾 (2 positive vs 2 negative，各 ≥2)
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 1 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status
PubMed studies (7)L2 · primary research & systematic reviews
Selenium supplementation for the primary prevention of cardiovascular disease
Finding: Selenium supplementation produced a small, non-significant increase in type 2 diabetes risk (RR 1.06, 95% CI 0.97 to 1.15) and no benefit on CVD mortality (RR 0.97, 95% CI 0.79 to 1.2), with authors noting a possible diabetes risk that cannot be ruled out in selenium-replete people.
View on PubMed Selenium exposure and the risk of type 2 diabetes: a systematic review and meta-analysis
Finding: Higher selenium was associated with greater T2D risk in observational data (RR 3.6, 95% CI 1.4-9.4 at 140 vs <45 µg/L) and selenium supplementation increased diabetes risk by 11% in RCTs (RR 1.11, 95% CI 1.01-1.22).
View on PubMed Selenium supplementation and the risk of type 2 diabetes mellitus: a meta-analysis of randomized controlled trials
Finding: Selenium supplementation showed no significant effect on T2D risk, with a non-significant trend toward increased risk (RR 1.09, 95% CI 0.99-1.20, p=0.085), and the authors did not support routine selenium supplementation for T2D prevention.
View on PubMed Effects of long-term selenium supplementation on the incidence of type 2 diabetes: a randomized trial
Finding: Selenium supplementation significantly increased incident type 2 diabetes (HR 1.55, 95% CI 1.03-2.33; 12.6 vs 8.4 cases/1000 person-years), with the effect concentrated in the highest baseline plasma-selenium tertile (HR 2.70, 95% CI 1.30-5.61).
View on PubMed Association between Serum Selenium Level and the Presence of Diabetes Mellitus: A Meta-Analysis of Observational Studies
Finding: High serum selenium was significantly associated with greater odds of diabetes (pooled OR 1.88, 95% CI 1.44-2.45), though the observational design cannot establish causation or direction.
View on PubMed Association between serum selenium level and type 2 diabetes mellitus: a non-linear dose-response meta-analysis of observational studies
Finding: T2D prevalence was higher in the highest vs lowest selenium category (OR 1.63, 95% CI 1.04-2.56, p=0.033) with a significant U-shaped non-linear relationship (p<0.001), risk rising at both low (<97.5 µg/L) and high (>132.5 µg/L) selenium.
View on PubMed Effectiveness and safety of selenium supplementation for type 2 diabetes mellitus in adults: a systematic review of randomised controlled trials
Finding: Individual small RCTs showed selenium lowered fasting insulin (MD -3.6 to -5.8 µIU/mL) and HOMA-IR (MD -1.0 to -1.6), but the review concluded there is no evidence supporting effectiveness of selenium supplementation in the T2D population.
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↗
L5d Harvard Health
Against
Selenium also appears to increase the risk of diabetes, and earlier studies dashed preliminary hopes that the supplement might protect against heart attacks. source↗
L5e Specialty Society (condition-mapped)
Against
Supplementation with micronutrients (e.g., vitamins and minerals, such as magnesium or chromium) or herbs or spices (e.g., cinnamon and aloe vera) is not recommended for glycemic benefits. Without underlying deficiency, there is no benefit from herbal or nonherbal (i.e., vitamin or mineral) supplementation for people with diabetes. source↗