Association between Serum Vitamin C and the Blood Pressure: A Systematic Review and Meta-Analysis of Observational Studies

Background . Hypertension is regarded as a major and independent risk factor of cardiovascular diseases, and numerous studies observed an inverse correlation between vitamin C intake and blood pressure. Aim . Our aim is to investigate the relationship between serum vitamin C and blood pressure, including the concentration differences and the correlation strength. Method . Two independent researchers searched and screened articles from the National Library of Medicine, Cochrane Library, Web of Science, China National Knowledge Infrastructure, VIP databases, and WANFANG databases. A total of 18 eligible studies were analyzed in the Reviewer Manager 5.3 software, including 14 English articles and 4 Chinese articles. Results . In the evaluation of serum vitamin C levels, the concentration in hypertensive subjects is 15.13 μ mol/L lower than the normotensive ones (mean difference=−15.13, 95% CI [-24.19, -6.06], and P=0.001). Serum vitamin C has a significant inverse relation with both systolic blood pressure (Fisher’s Z=−0.17, 95% CI [-0.20, -0.15], P<0.00001) and diastolic blood pressure (Fisher’s Z=−0.15, 95% CI [-0.20, -0.10], P<0.00001). Conclusions . People with hypertension have a relatively low serum vitamin C, and vitamin C is inversely associated with both systolic blood pressure and diastolic blood pressure.