Johns Hopkins School of Medicine, Johns Hopkins Bloomberg School of Public Health, and Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins Medical Institutions, Baltimore, MD 21205, USA.
Am J Clin Nutr. 2012 May;95(5):1079-88. doi: 10.3945/ajcn.111.027995. Epub 2012 Apr 4.
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.
在观察性研究中，增加维生素 C 的摄入、补充维生素 C 和提高血液中维生素 C 的浓度与降低血压（BP）有关。然而，临床试验中维生素 C 降低血压效果的证据并不一致。
系统评价和荟萃分析维生素 C 补充剂对血压影响的临床试验。
我们检索了 1966 年至 2011 年期间的 Medline、EMBASE 和中央数据库。预先设定的纳入标准如下：1）使用随机对照试验设计；2）试验报告了收缩压（SBP）或舒张压（DBP）或两者的影响；3）试验使用口服维生素 C 和对照试验组；4）试验持续时间至少 2 周。通过随机效应模型对血压影响进行汇总，试验权重为逆方差。
29 项试验符合主要分析的纳入标准。中位数剂量为 500mg/d，中位数持续时间为 8 周，试验规模从 10 到 120 名参与者不等。SBP 和 DBP 的汇总变化分别为-3.84mmHg（95%CI：-5.29，-2.38mmHg；P<0.01）和-1.48mmHg（95%CI：-2.86，-0.10mmHg；P=0.04）。在高血压参与者的试验中，SBP 和 DBP 的相应降低分别为-4.85mmHg（P<0.01）和-1.67mmHg（P=0.17）。纳入 9 项具有推测血压影响的试验后，血压效应减弱，但仍有统计学意义。
在短期试验中，维生素 C 补充剂降低了 SBP 和 DBP。需要进行长期试验来研究维生素 C 补充剂对血压和临床事件的影响。
