Randomized controlled trial for an effect of catechin-enriched green tea consumption on adiponectin and cardiovascular disease risk factors

BACKGROUND Previous observational studies have indicated that green tea (GT) consumption is associated with reduced mortality from cerebral infarction but not with mortality from cerebral hemorrhage. Therefore, we hypothesized that GT exerts a direct antiatherosclerotic effect without any effect on hypertension. To investigate this hypothesis, we focused on adiponectin that seems to be among the several key players in atherosclerosis. OBJECTIVE The objective of this randomized controlled trial (RCT) was to assess whether the consumption of catechin-enriched GT affects serum adiponectin levels and cardiovascular disease (CVD) risk factors among apparently healthy subjects. DESIGN A total of 51 individuals participated in the study. Eligible participants were randomly assigned into GT consumption groups with either high catechin (400 mg/day) or low catechin (100 mg/day). The study participants were asked to stop GT consumption for 2 weeks (washout period), following which they were to start drinking the provided GT beverages everyday for 9 weeks. The outcome measures were changes in the adiponectin levels and CVD risk factors (body weight, body mass index, waist circumference, blood pressure, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglyceride, fasting plasma glucose, as well as aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transpeptidase, uric acid, and high-sensitive C-reactive protein). RESULTS After intervention for 9 weeks, we found no significant difference between the high- and low catechin group with respect to changes in the serum adiponectin level: 0.35 µg/ml (95% confidence interval (CI): -1.03, 1.74). Also, no significant difference was observed between the high- and low catechin groups with respect to changes in any of the measured CVD risk factors. CONCLUSION This RCT showed no significant difference between the high- and low catechin groups with respect to changes in the serum adiponectin level and any CVD risk factors.