Vitamin D for Common Cold
Verdict: Published with Warning
Across 6 PubMed studies, the evidence for Vitamin D in Common Cold grades Tier C — weak evidence. Effective, but with safety or population caveats.
C 🟠 C Weak Evidence Published with Warning
Why this grade7-layer evidence engine
⚖️
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditableRaw score 0.46
D
C
B
A
S
← counter-evidence / ineffectiveeffective / strong evidence →
Final grade
C · Published with Warning
Confidence
77%
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 = 0.463
- 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 > 1 positive)，下層 RCT 不能推翻
- apply_hec_override — HEC-1 高階證據 negative — 強制由 C 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
Vitamin D for preventing acute respiratory infections in children up to five years of age
Finding: Vitamin D vs placebo may slightly reduce the proportion of children making ARI-related healthcare visits (RR 0.95, 95% CI 0.91-1.00, P=0.03; 10 studies, 2447 participants, low-certainty) but probably does not reduce the mean number of ARI visits per child (MD 0.07, 95% CI -0.06 to 0.20, P=0.32; moderate-certainty), and higher vs lower dose shows no benefit (RR 0.94, 95% CI 0.81-1.10).
View on PubMed Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data
Finding: Vitamin D reduced ARI risk overall (adjusted OR 0.88, 95% CI 0.81-0.96), with benefit confined to daily/weekly dosing without bolus (aOR 0.81, 0.72-0.91; bolus aOR 0.97, 0.86-1.10, p-interaction=0.05) and strongest in those with baseline 25(OH)D <25 nmol/L (aOR 0.30, 0.17-0.53 vs aOR 0.75 for >=25 nmol/L, p-interaction=0.006).
View on PubMed Vitamin D supplementation to prevent acute respiratory infections: a systematic review and meta-analysis of aggregate data from randomised controlled trials
Finding: Vitamin D produced a small but significant reduction in ARI risk (OR 0.92, 95% CI 0.86-0.99; 37 studies; I2=35.6%), with stronger protection in the daily-dosing (OR 0.78, 0.65-0.94), daily 400-1000 IU (OR 0.70, 0.55-0.89), <=12-month, and age 1-15.99 yr subgroups; no effect modification by baseline 25(OH)D and serious-adverse-event OR 0.97 (0.86-1.07).
View on PubMed Vitamin D supplementation to prevent acute respiratory infections: systematic review and meta-analysis of stratified aggregate data
Finding: After adding 6 newer RCTs the protective effect was no longer statistically significant (OR 0.94, 95% CI 0.88-1.00, p=0.057; 40 studies; 61,589 participants; I2=26.4%), with no effect modification by age, baseline 25(OH)D, dosing frequency, or dose, and a left-asymmetric funnel plot (Egger p=0.0020) suggesting prior estimates were inflated by small-study/publication bias.
View on PubMed Effect of Daily Vitamin D Supplementation on Risk of Upper Respiratory Infection in Older Adults: A Randomized Controlled Trial
Finding: In generally healthy older adults not selected for deficiency, daily vitamin D3 2000 IU did not lower URI risk (OR 0.96, 95% CI 0.86-1.06), and even the prespecified deeply-deficient subgroup (<12 ng/mL, n=255) was nonsignificant (OR 0.60, 95% CI 0.28-1.30).
View on PubMed Efficacy of Vitamin D Supplements in Prevention of Acute Respiratory Infection: A Meta-Analysis for Randomized Controlled Trials
Finding: Overall no significant ARI prevention (RR 0.96, 95% CI 0.91-1.01; I2=59.0%); apparent benefit of daily (RR 0.83, 0.73-0.95) and short-term dosing disappeared when restricted to high-quality trials (RR 0.89, 0.78-1.02 by Jadad; RR 0.87, 0.66-1.15 by Cochrane RoB), with publication bias observed.
View on PubMed Regulatory & authoritative positionsL4/L5 · FDA / EMA / NIH ODS / Cochrane / Mayo …
L4a US FDA
Supportive
Vitamin D-3 is recognized as GRAS source↗
L4b EU EFSA
Supportive
cause and effect relationship has been established source↗
L4c UK NHS
Supportive
everyone should consider taking a daily vitamin D supplement during the autumn and winter source↗
L4d TW TFDA / 衛福部
Supportive
每日維生素D攝取量需達10微克 source↗
L4e WHO
Cautious
not recommended for all pregnant women source↗
L5a NIH Office of Dietary Supplements
Supportive
Vitamin D is a fat-soluble vitamin source↗
L5b Mayo Clinic
Cautious
Vitamin D has properties that support your immune system. ... Most clinical studies of vitamin D in COVID-19 have been observational, and few randomized controlled trials of vitamin D supplementation have been completed, with those that have been completed showing no benefit of vitamin D in hospitalized patients. source↗
L5c Cleveland Clinic
Cautious
Vitamin D has been shown to help regulate the immune system, and low vitamin D levels is associated with a higher risk of infections, especially those that affect the respiratory system. source↗
L5d Harvard Health
Cautious
there is no consistent evidence to support the use of vitamins C and D, echinacea, and ginseng source↗
L5e Specialty Society (condition-mapped)
Cautious
People with low vitamin D levels might be more likely to get respiratory infections and might have a higher chance of dying from these infections. Some studies suggest that taking vitamin D supplements regularly might slightly reduce the risk of getting a respiratory infection, especially in people with low vitamin D levels. source↗