Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials.
What this study found
Vitamin C supplementation was associated with lower blood pressure in short-term randomized trials, suggesting a potential antihypertensive effect. In the pooled analysis, systolic BP decreased by 23.84 mm Hg (95% CI: 25.29, 22.38; P < 0.01) and diastolic BP by 21.48 mm Hg (95% CI: 22.86, 20.10; P = 0.04). In hypertensive participants, systolic BP fell by 24.85 mm Hg (P < 0.01), while the diastolic effect was not significant (21.67 mm Hg; P = 0.17). Sensitivity analyses remained favorable, including imputed analyses for SBP and DBP and analyses excluding trials with missing baseline BP data.…
- Study & population
- Systematic review and random-effects meta-analysis of randomized controlled trials in adults.
- Intervention
- Oral vitamin C supplementation was evaluated across 29 randomized trials.
- Key limitation
- Evidence was heterogeneous across trials, and most studies were short term, with durations of 2 to 26 wk.
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Open PDFOriginal abstract
BACKGROUND In observational studies, increased vitamin C intake, vitamin C supplementation, and higher blood concentrations of vitamin C are associated with lower blood pressure (BP). However, evidence for blood pressure-lowering effects of vitamin C in clinical trials is inconsistent. OBJECTIVE The objective was to conduct a systematic review and meta-analysis of clinical trials that examined the effects of vitamin C supplementation on BP. DESIGN We searched Medline, EMBASE, and Central databases from 1966 to 2011. Prespecified inclusion criteria were as follows: 1) use of a randomized controlled trial design; 2) trial reported effects on systolic BP (SBP) or diastolic BP (DBP) or both; 3) trial used oral vitamin C and concurrent control groups; and 4) trial had a minimum duration of 2 wk. BP effects were pooled by random-effects models, with trials weighted by inverse variance. RESULTS Twenty-nine trials met eligibility criteria for the primary analysis. The median dose was 500 mg/d, the median duration was 8 wk, and trial sizes ranged from 10 to 120 participants. The pooled changes in SBP and DBP were -3.84 mm Hg (95% CI: -5.29, -2.38 mm Hg; P < 0.01) and -1.48 mm Hg (95% CI: -2.86, -0.10 mm Hg; P = 0.04), respectively. In trials in hypertensive participants, corresponding reductions in SBP and DBP were -4.85 mm Hg (P < 0.01) and -1.67 mm Hg (P = 0.17). After the inclusion of 9 trials with imputed BP effects, BP effects were attenuated but remained significant. CONCLUSIONS In short-term trials, vitamin C supplementation reduced SBP and DBP. Long-term trials on the effects of vitamin C supplementation on BP and clinical events are needed.