Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials.
PubMed 22492364 · doi:10.3945/ajcn.111.027995
What was done
Systematic review and meta-analysis of randomized controlled trials searching Medline, EMBASE, and Central from 1966 to 2011. Included studies were randomized controlled trials comparing oral vitamin C supplementation against concurrent control groups for at least 2 weeks that reported systolic blood pressure (SBP) or diastolic blood pressure (DBP) or both. Effects were pooled using random-effects models weighted by inverse variance.
What was found
Twenty-nine trials met primary analysis eligibility criteria (median dose 500 mg/d, median duration 8 wk, sample sizes 10 to 120 participants). Pooled changes were -3.84 mm Hg for SBP (95% CI: -5.29, -2.38 mm Hg; P < 0.01) and -1.48 mm Hg for DBP (95% CI: -2.86, -0.10 mm Hg; P = 0.04). In hypertensive participants, reductions were -4.85 mm Hg for SBP (P < 0.01) and -1.67 mm Hg for DBP (P = 0.17). Including 9 trials with imputed BP effects attenuated the findings, but results remained significant.
Why it matters
This study provides evidence that short-term vitamin C supplementation yields modest reductions in both systolic and diastolic blood pressure.
Limits
Included trials had small sample sizes (10 to 120 participants) and short follow-up periods (median 8 weeks). The reduction in diastolic blood pressure was not statistically significant among hypertensive participants (P = 0.17). Long-term effects and clinical cardiovascular outcomes were not evaluated.
Cited by
- supports A meta-analysis of 29 randomized placebo-controlled clinical trials found that an average of 500 milligrams of oral vitamin C daily for eight weeks significantly decreased blood pressure in hypertensive patients.