Association between Serum Vitamin C and the Blood Pressure: A Systematic Review and Meta-Analysis of Observational Studies
Ran Li, Wenli Zhao, Xiaodong Tan, Hongwu Wang, Kaito Mizuno, Ken Takagi, Ye Zhao, Huaien Bu
Abstract
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 (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mtext>mean</mml:mtext><mml:mtext> </mml:mtext><mml:mtext>difference</mml:mtext><mml:mrow><mml:mo>=</mml:mo></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow><mml:mn>15.13</mml:mn></mml:math>, 95% CI [-24.19, -6.06], and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mi>P</mml:mi><mml:mo>=</mml:mo><mml:mn>0.001</mml:mn></mml:math>). Serum vitamin C has a significant inverse relation with both systolic blood pressure (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mtext>Fishe</mml:mtext><mml:msup><mml:mrow><mml:mtext>r</mml:mtext></mml:mrow><mml:mrow><mml:mtext>’</mml:mtext></mml:mrow></mml:msup><mml:mtext>s</mml:mtext><mml:mtext> </mml:mtext><mml:mi>Z</mml:mi><mml:mrow><mml:mo>=</mml:mo></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow><mml:mn>0.17</mml:mn></mml:math>, 95% CI [-0.20, -0.15], <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mi>P</mml:mi><mml:mo><</mml:mo><mml:mn>0.00001</mml:mn></mml:math>) and diastolic blood pressure (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M5"><mml:mtext>Fishe</mml:mtext><mml:msup><mml:mrow><mml:mtext>r</mml:mtext></mml:mrow><mml:mrow><mml:mtext>’</mml:mtext></mml:mrow></mml:msup><mml:mtext>s</mml:mtext><mml:mtext> </mml:mtext><mml:mi>Z</mml:mi><mml:mrow><mml:mo>=</mml:mo></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow><mml:mn>0.15</mml:mn></mml:math>, 95% CI [-0.20, -0.10], <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M6"><mml:mi>P</mml:mi><mml:mo><</mml:mo><mml:mn>0.00001</mml:mn></mml:math>). 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.