Vitamin C supplementation significantly reduces blood pressure in adults, meta-analysis shows
- Meta-analysis of 29 randomized, controlled trials (1,407 adults)
- Vitamin C supplementation significantly reduces blood pressure
- Median dosage is 500 mg/day for 8 weeks
This meta-analysis was designed to investigate the effect of vitamin C supplementation on blood pressure (BP) in adults.
A search of Medline, EMBASE, and the Cochrane Central Register of Controlled Trials databases was performed for articles published from January 1966 to December 2010. Inclusion criteria included only randomized, controlled trials that involved adults who supplemented with vitamin C (except in calorie-containing beverages) that lasted from at least 2 weeks up to one year with robust data on changes in BP. Studies with adults who were pregnant or had end-stage renal disease were excluded.
The primary analysis was the between-group differences in BP change for vitamin C and placebo groups. BP effects were pooled by random-effects models, with trials weighted by inverse variance. Heterogeneity was assessed with I-squared (I2) and Cochrane’s Q tests. Publication bias and subgroup analyses were also performed.
A total of 29 clinical trials with 1,407 participants met the inclusion criteria for the primary analysis. The median dose was 500 mg/day, the median duration was 8 weeks, and trial sizes ranged from 10 to 120 participants.
In pooled analyses, vitamin C supplementation significantly reduced systolic BP by -3.84 mm Hg (95% CI: -5.29, -2.38 mm Hg; P<.01) and diastolic BP by -1.48 mm Hg (95% CI: -2.86, -0.10 mm Hg; P=.04). Both systolic and diastolic BP pooled effects were heterogeneous (I2 of 69% and 81% respectively; both P<.001). BP effects did not differ by hypertensive status for either systolic and diastolic BP. The authors report no evidence of publication bias.
These findings suggest that short-term vitamin C supplementation (500 mg/day for 8 weeks) may offer clinical value for adults to help maintain normal blood pressure.