Green tea catechins and blood pressure: a systematic review and meta-analysis of randomised controlled trials

Abstract

Purpose Although previous literature has reported that regular green tea consumption may improve blood pressure, the evidence from these studies is not consistent. The present study systematically reviewed randomised controlled trials and examined the effect of green tea consumption on blood pressure using meta-analysis. Methods Search of ProQuest, PubMed, Scopus and Cochrane Library (CENTERAL) was conducted, to identify eligible articles. Articles from 1995 to 2013 were included. A random-effect model was chosen to calculate the effect of combined trials. Result Thirteen studies were included in the meta-analysis. Green tea consumption significantly changed systolic blood pressure, by -2.08 mm Hg (95 % CI -3.06, -1.05), and diastolic blood pressure, by -1.71 mm Hg (95 % CI -2.86, -0.56), compared to the control. Changes in lipid profile, blood glucose and body mass index were also assessed in the meta-analysis. A significant reduction was found in total cholesterol (-0.15 mmol/L [95 % CI -0.27, -0.02]) and low-density lipoprotein cholesterol (-0.16 mmol/L [95 % CI -0.22, -0.09]). Changes in other parameters did not reach statistical significance. Subgroup analysis suggested a greater reduction in both systolic and diastolic blood pressure in studies that included participants with a baseline mean systolic blood pressure of =130 mm Hg, and studies involving consuming green tea as an extract. Conclusion The present meta-analysis suggests that green tea and its catechins may improve blood pressure, and the effect may be greater in those with systolic blood pressure =130 mm Hg. The meta-analysis also suggests that green tea catechins may improve total and low-density lipoprotein cholesterol.