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Vitamin C for Hypertension

Verdict: Published with Warning

Across 5 PubMed studies, the evidence for Vitamin C in Hypertension grades Tier B — preliminary evidence. Effective, but with safety or population caveats.

B 🟡 B Preliminary Evidence Published with Warning

🔬Why this grade7-layer evidence engine

⚖️

Scoring transparency

All scores computed by a 7-layer evidence engine — fully auditable
Raw score 0.60
D
C
B
A
S
← counter-evidence / ineffectiveeffective / strong evidence →
Final grade
B · Published with Warning
Confidence
84%
Highly consistent evidence
Evidence level
E2
Multiple high-quality MAs (≥2 independent, consistent)

How strongly each layer supports this effect

lower = less supportive
L5 Clinical bodiesAuthoritative stance
0.45
L1 ExamineGlobal benchmark
0.50
L11 AI re-checkIndependent read
0.50
L3 MechanismPlausibility
0.65
L2 PubMedPrimary literature
0.75
Against Mixed Supports
▸View the full decision path (audit trail)
  1. compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.6
  2. tier_from_score — 依分數區間映射至 tier letter
  3. apply_hec_rules — 高品質 SR/MA 顯示 positive (2 篇 > 1 negative)
  4. tier_strict_requirement_check — Tier 條件達標，未降階
  5. detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
  6. decide_status — 依 tier + dispute 結果決定 status

📄PubMed studies (5)L2 · primary research & systematic reviews

Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials
PMID: 22492364 2012 統合分析
Finding: Pooled vitamin C supplementation reduced SBP by -3.84 mmHg (95% CI -5.29 to -2.38; P<0.01) and DBP by -1.48 mmHg (95% CI -2.86 to -0.10; P=0.04), with a larger SBP drop of -4.85 mmHg in hypertensive participants.
Government Effect size: SBP WMD -3.84 mmHg (95% CI -5.29, -2.38); DBP -1.48 mmHg (95% CI -2.86, -0.10); hypertensives SBP -4.85 mmHg
View on PubMed
The effect of vitamin C supplementation on blood pressure in adults: an umbrella review of meta-analyses of randomized clinical trials
PMID: 41784995 2026 系統性回顧
Finding: Vitamin C may reduce SBP by approximately 3.7 mmHg with no overall DBP reduction (a -2.27 mmHg DBP drop only in diabetics), but the GRADE certainty of evidence was rated LOW, so larger long-term RCTs are needed.
Effect size: SBP approx -3.7 mmHg; DBP null overall; diabetics DBP -2.27 mmHg; GRADE certainty = low
View on PubMed
Vitamin C supplementation showed greater effects on systolic blood pressure in hypertensive and diabetic patients: an updated systematic review and meta-analysis of randomised clinical trials
PMID: 37791386 2023 統合分析 n = 890
Finding: Vitamin C reduced SBP by -3.0 mmHg (95% CI -4.7 to -1.3; p=0.001) with a more pronounced effect in hypertensives (-3.2 mmHg, p=0.002) and diabetics (-4.6 mmHg, p=0.03); DBP effect was not emphasized.
Effect size: SBP -3.0 mmHg (95% CI -4.7, -1.3); hypertensives -3.2 mmHg; diabetics -4.6 mmHg
View on PubMed
Effects of vitamin C supplementation on essential hypertension: A systematic review and meta-analysis
PMID: 32080138 2020 統合分析 n = 614
Finding: In essential hypertension, vitamin C lowered SBP by -4.09 mmHg (95% CI -5.56 to -2.62; P<0.001) and DBP by -2.30 mmHg (95% CI -4.27 to -0.33; P=0.02), with a stronger SBP effect at doses >=500 mg/d (-5.01 mmHg).
Effect size: SBP WMD -4.09 mmHg (95% CI -5.56, -2.62); DBP -2.30 mmHg (95% CI -4.27, -0.33); >=500 mg/d SBP -5.01 mmHg
View on PubMed
Association between Serum Vitamin C and the Blood Pressure: A Systematic Review and Meta-Analysis of Observational Studies
PMID: 32426036 2020 統合分析
Finding: Hypertensive subjects had serum vitamin C 15.13 umol/L lower than normotensives (MD -15.13, 95% CI -24.19 to -6.06; P=0.001), with significant inverse correlations for SBP (Fisher's Z -0.17, P<0.00001) and DBP (Fisher's Z -0.15, P<0.00001).
🟠 Limited quality Effect size: Serum difference MD -15.13 umol/L (95% CI -24.19, -6.06); SBP Fisher's Z -0.17; DBP Fisher's Z -0.15
View on PubMed

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

L4a US FDA
Supportive
Consumption of antioxidant vitamins may reduce the risk of certain kinds of cancer. source↗
L4b EU EFSA
Supportive
A cause and effect relationship has been established between the dietary intake of vitamin C and protection of DNA, proteins and lipids from oxidative damage. source↗
L4c UK NHS
Cautious
You should be able to get all the vitamin C you need by eating a varied and balanced diet. If you take vitamin C supplements, do not take too much as this could be harmful. source↗
L4d TW TFDA / 衛福部
Supportive
成人每日需要的攝取量為100毫克、孕婦每日120毫克、哺乳媽媽每日140毫克 source↗
L4e WHO
Neutral
Vitamin E and C supplementation is not recommended for pregnant women to improve maternal and perinatal outcomes. source↗
L5a NIH Office of Dietary Supplements
Supportive
Vitamin C plays an important role in immune function and improves the absorption of nonheme iron. source↗
L5b Mayo Clinic
Neutral
Taking vitamin C supplements doesn't seem to affect heart disease risk. Although vitamin C is being used to reduce the risk of cardiovascular disease and certain types of cancer, there is not enough information to show that these uses are effective. source↗
L5c Cleveland Clinic
Supportive
Foods high in vitamin C, vitamin E, potassium, selenium or L-arginine are good options if you're looking to lower your blood pressure. Foods high in vitamin C: Protect against oxidative stress, which causes inflammation. source↗
L5d Harvard Health
Cautious
Vitamin C supplements might have a modest effect on blood pressure. However, clinical trials testing vitamin C supplements have not shown consistent benefits in preventing or reducing heart disease. source↗
L5e Specialty Society (condition-mapped)
Against
Avoid antioxidant vitamin supplements such as A, C and E. Scientific evidence does not support their benefit to blood pressure, lower blood cholesterol or stop smoking. source↗
✓PMID 100% verifiedevery citation checked via NCBI Entrez
🔬5 PubMed studiesindependently re-checked by multiple sub-agents
engine_version: v1.0 claim_id: CLM-COND-hypertension-INT-vitamin-c-001 繁體中文版 →