Objective: The aim of this study is to evaluate the effects of green tea on blood pressure only in healthy individuals by synthesizing randomized controlled studies in order to reduce the effect of possible confounding factors.
Methods: CINAHL, Cochrane Central, Medline/PubMed, Web of Science, Science Direct, YÖK National Thesis Center, and ULAKBİM electronic databases; the keywords, "green tea," "Camellia sinensis," "EGCG," "blood pressure," "systolic blood pressure," "diastolic blood pressure," and "randomized controlled trial," were searched systematically. The risk of eligible studies was evaluated by two researchers using the Cochrane Collaboration risk-of-bias tool.
Results: The total sample size of the 9 studies included in the meta-analysis was 680 (experimental: 345, control: 335), the mean age of the individuals in the intervention group was 35.89 ± 8.52, while the mean age of the control group was 36.48 ± 7.68. All studies clearly described allocation randomization, none had incomplete outcome data, and all used appropriate statistical analysis. The completion rate of the consumption of green tea ranged from 85-100%. The combined results of the studies showed that green tea was effective in lowering systolic and diastolic blood pressure in individuals (MD: -2.99, 95%; CI: -3.77 to -2.22; Z = 7.57; P < .00001; I2 = 0%, MD: -0.95, 95%; CI: -1.62 to -0.27; Z = 2.75; P = .006; I2 = 0%). No publication bias was observed in the studies.
Conclusion: In healthy individuals, green tea supplementation reduced systolic blood pressure by 2.99 mmHg and diastolic blood pressure by 0.95 mmHg. Our study allowed us to clearly evaluate the effect of green tea as it included healthy individuals and contributed to the literature. Considering that atherometabolic diseases are the leading cause of mortality and disability today, it is important to explain the metabolic benefits of green tea, which is easily accessible and cheap, to society.