Effect Of Black Tea On Blood Pressure

BackgroundHypertension is a major risk factor for CVD and is strongly linked to ischemic heart prevalence exceeding 1 billion.Furthermore,hypertension is recognized as one of the leading risk factors for global disease burden.Studies have shown that a 10 mm Hg reduction in systolic blood pressure(SBP)reduced the risk of major cardiovascular disease events by 20%,and even small changes in BP caused by dietary modification might have a significant impact on the onset of CVD and stroke.It has been shown that specific nutrients help in lowering blood pressure.Numerous studies have shown the antihypertensive effects of black tea in different preclinical models of hypertension.In previous reports,administration of black tea attenuated blood pressure levels and endothelial dysfunction in rats.Moreover,results of population studies indicate that a higher intake of black tea can protect against hypertension and cardiovascular disease.While some clinical trials revealed some beneficial effects of black tea supplementation on blood pressure,others failed to find such an influence.Today,available studies reach conflicting data,probably due to their heterogeneous methods and the fact that they were small RCTs.PurposeDespite previous investigations on the effects of black tea supplementation on blood pressure,inconsistent findings are available in this regard.Therefore,we conducted a systematic review and meta-analysis of randomized clinical trials on the effect of black tea supplementation on blood pressure(BP)in adults.Methods Relevant studies published up to March 2020 were searched through PubMed,Embase and Cochrane Library using suitable keywords.All randomized clinical trials(RCTs)that examined the effect of black tea supplementation on systolic blood pressure(SBP)or diastolic blood pressure(DBP)in adults were included.Two review authors independently extracted data on study characteristics,methods and outcomes.Overall,the impact of black tea on BP was reported in 22 study arms.ResultsOverall,thirteen trials,including twenty-two study arms were included in our study.Black tea supplementation significantly reduced SBP and DBP compared to the control[weighted mean differences(WMD)-1.04 mmHg;95%CI-2.05 to-0.03;P=0.04].(WMD-0.59 mmHg;95%CI-1.05 to-0.13;P=0.01).Further,there was a significant difference in the SBP and DBP for the subgroup with more male participants and that conducted in European countries.In the subgroup analysis,results for SBP and DBP with a study duration?1 weeks and black tea flavonoids supplementation at the dose between 200 mg/day and 800 mg/day was statistically significant different.However,nonlinear analysis failed to indicate a significant influence of black tea flavonoids supplementation dose or duration on both SBP and DBP.Sensitivity analysis showed that no individual study had a significant impact on our final results.In addition,we found no evidence for the presence of small-study effects among studies for both SBP and DBP.Conclusion1.Black tea supplementation can lower blood pressure,and results were stable and reliable in sensitivity analysis.2.The effect of black tea intake on lowering blood pressure was more significant when used in longer duration(>7 days)and in men.Further RCTs using different doses of black tea and in various durations are required to confirm our conclusion.3.Based on the above conclusions,it is currently believed that black tea supplementation may play an important role in lowering blood pressure in population.