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.
The objective was to conduct a systematic review and meta-analysis of clinical trials that examined the effects of vitamin C supplementation on BP.
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.
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.
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.
Am J Clin Nutr. 2012 May;95(5):1079-88. doi: 10.3945/ajcn.111.027995. Epub 2012 Apr 4.
Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials.
Juraschek SP1, Guallar E, Appel LJ, Miller ER 3rd.