A organized review and also meta-analysis of randomized managed trials

Xu, Renfan MD, PhDa; Yang, Ke MDb; Ding, Jie MDb; Chen, Guangzhi MD, PhDb,∗Editor(s): Omboni., Stefano

author Information

aDepartment of clinical Ultrasound

bDivision of Cardiology, department of internal Medicine, Tongji Hospital, Tongji clinical College, Huazhong college of Science and Technology, Wuhan, P.R. China.

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∗Correspondence: Guangzhi Chen, department of Cardiology, room of interior Medicine, Tongji Hospital, Tongji medical College, Huazhong university of Science and Technology, Wuhan 430030, P.R. China (e-mail: ).

Abbreviations: BP = blood pressure, CI = trust interval, CVD = cardiovascular disease, DBP = diastolic blood pressure, EGCG = epigallocatechin gallate, MD = mean difference, PRISMA = desired reporting items for systematic reviews and meta-analyses, RCT = randomized placebo-controlled trial, SBP = systolic blood pressure, SD = traditional deviation, SE = traditional error.

How to cite this article: Xu R, Yang K, Ding J, Chen G. Result of eco-friendly tea supplementation ~ above blood pressure: A methodical review and also meta-analysis of randomized controlled trials. Medicine. 2020;99:6(e19047).

The current study was sustained by the National natural Science foundation of China (No. 81500293).

The authors have actually no problems of attention to disclose.

This is one open accessibility article dispersed under the terms of the creative Commons Attribution-Non Commercial license 4.0 (CCBY-NC), wherein it is permissible to download, share, remix, transform, and buildup the work detailed it is properly cited. The work-related cannot be offered commercially there is no permission native the journal. Http://creativecommons.org/licenses/by-nc/4.0

Medicine: February 2020 - Volume 99 - issue 6 - ns e19047
doi: 10.1097/MD.0000000000019047
open Metrics



Although proof from animal and also observational studies has supported the beneficial effects of environment-friendly tea intake for lowering blood press (BP), randomized placebo-controlled trials (RCTs) have actually yielded conflict results. In this meta-analysis that RCTs, us aimed to assess the impacts of environment-friendly tea supplementation on measures of BP control.


The PubMed, Embase, and Cochrane Library databases to be electronically searched native inception to august 2019 for all pertinent studies. The outcomes were pooled making use of the share inverse-variance an approach with random-effects weighting and also expressed together mean distinctions (MDs) with 95% to trust intervals (CIs). The quality of research studies was assessed using the Jadad score. Publication prejudice was evaluated making use of funnel plots, Egger test, and Begg test.


Twenty-four trials with 1697 topics were had in the meta-analysis. The pooled results showed that eco-friendly tea considerably lowered systolic BP (SBP; MD: −1.17 mm Hg; 95%CI: −2.18 to −0.16mm Hg; P = .02) and diastolic BP (DBP; MD: −1.24 mm Hg; 95%CI:−2.07 to −0.40mm Hg; P = .004). Far-ranging heterogeneity was found for both SBP (I2 = 43%) and DBP (I2 = 57%). In addition, no evidence of significant publication predisposition was found from funnel plots or Egger check (P = .674 and P = .270 because that SBP and also DBP, respectively).


Overall, eco-friendly tea significantly reduced SBP and also DBP over the term of the temporary trials. Larger and longer-term trials are necessary to further investigate the effects of eco-friendly tea supplementation ~ above BP control and also clinical events.

1 Introduction

Cardiovascular an illness (CVD) is the leading cause of morbidity, mortality, and also disability worldwide.<1> Hypertension is 1 of the leading causes of cardiovascular events<2,3> and the main contributor to 7 million deaths annually worldwide.<4> The risk of CVD doubles for each increment the 20/10 mm Hg in blood pressure (BP)from as low together 115/75 mm Hg.<5> virtually 50% that ischemic heart condition cases and also 60% of stroke instances are attributed to elevated BP.<6> researches have shown that even a modest palliation in BP is clinically relevant in to reduce the hazard of coronary heart diseases and also stroke.<7>

Lifestyle changes have been shown to be reliable in regulation BP.<8> In particular, nutrition therapies have actually shown useful effects because that the prevention and also control of hypertension. Eco-friendly tea, obtained from the tree Camellia sinensis, is a extensively consumed beverage worldwide and is traditionally supplied in eastern countries as a medication. The mechanisms underlying the helpful effects of environment-friendly tea are mainly attributed to its flavonoid-like polyphenol components such as catechins. Catechins mainly incorporate epigallocatechin gallate (EGCG), epicatechin gallate, epigallocatechin, and epicatechin, which are the most common green tea extracts and also have been shown to be helpful to human being health.<9> In vitro researches have displayed that green tea catechins exert a cardioprotective impact through multiple mechanisms, consisting of the inhibition of oxidation, vascular inflammation, and thrombogenesis, as well as the innovation of endothelial dysfunction.<10,11> animal studies have also revealed that eco-friendly tea catechins influence nitric oxide production and vasodilation, thereby enhancing endothelial dysfunction and also hypertension in rodents.<10>

To date, plenty of longitudinal observational studies and intervention trials have actually investigated the association in between tea consumption and BP reduction; however, the results were controversial. Some researches reported that tea intake reduced BP,<12,13> whereas rather reported no significant change in BP manage with tea intake.<14> Thus, we conducted a meta-analysis that all published randomized placebo-controlled trials (RCTs) come quantitatively evaluate the result of green tea on procedures of BP reduction in accordance v the wanted reporting items for methodical reviews and meta-analyses (PRISMA) guidelines.

2 Methods

2.1 search strategy and also eligibility criteria

This organized review and also meta-analysis was conducted in accordance with the PRISMA declare guidelines.<15>We searched PubMed, Embase, and the Cochrane Library from the index day of each database v August 2019 by utilizing the complying with terms: “green tea”,“green tea extract”,“tea component(s)”, “tea solid(s)”, “catechin”, “catechins”, “EGCG”, “Camellia sinensis”, “tea polyphenols”, “blood pressure”, “hypertension”, “hypertensive”,“hypotension”,“hypotensive”,“endothelium”,“endothelial function”, and “endothelial dysfunction.” The find was minimal to RCTs in adult (age > 18 years). Language was minimal to English. The recommendation sections the all posts selected for inclusion and also those of ahead meta-analysis were hand-searched for additional articles.

2.2 study selection

The prespecified consist of criteria were as follows:

(1) Adult subjects who ingested eco-friendly tea beverages or extract for ≥2 weeks. (2) RCTs v either a parallel or crossover design. (3) The baseline and endpoint worths of systolic BP (SBP) or diastolic BP (DBP), or both, through standard deviations (SDs), standard errors (SEs), or 95% trust intervals (CIs) were accessible for each team in the study. (4) green tea extract was not administered as part of a multicomponent complement in either the experimental or control group. (5) The food intake manage regimens that the speculative groups were regular with those that the control groups, and the just difference in between the control and treatment teams was environment-friendly tea or environment-friendly tea extract supplementation; and also (6) Each team had > 10 subjects.

The exemption criteria were together follows:

(1) Trials that enrolled youngsters or pregnant women. (2) Review, meta-analysis, or abstract only; and also (3) Trials without details that the EGCG or polyphenol content of the environment-friendly tea. The data the multiple released reports native the same study populace were contained only once.

2.3 quality assessment

The top quality of research studies was assessed making use of the Jadad score with the adhering to criteria:

(1) Randomization, (2) twin blinding (participant and researcher masking), (3) reporting the variety of and factors for withdrawal, (4) assignment concealment, and also (5) Generation of arbitrarily numbers.

The trials to be scored 1 suggest for every area handle in the examine design, v a possible score of in between 0 and 5 (highest quality).<16> The trials were categorized together high high quality (Jadad score ≥4) or low top quality (Jadad score (1) Study features (authors, publication year, sample size, research duration, study design, treatment dose, and kind of intervention), participant characteristics (location, mean age or period range, sex, preexisting an illness or condition, and (2) Treatment v antihypertensive medications), and also details that the baseline and final SBP and also DBP measurements. For multi-arm studies, only intervention groups that met the consist of criteria were used in the analysis. If BP to be reported several times in different stages that the trials, just the last BP documents at the finish of the trials were extracted because that the meta-analysis.

2.5 statistics analysis

Statistical analysis was performed v RevMan version 5 software program (Cochrane Collaboration). The key outcome that the meta-analysis to be the mean distinction (MD) in BP (SBP and also DBP, mm Hg) between the intervention and control groups from baseline come the end of the intervention period. When SDs were not directly available, they were calculated indigenous SEs, 95% CIs, ns values, or t values.<17> In addition, the change-from-baseline SD values were imputed as said by Follmann et al, assuming a correlation coefficient the 0.5.<18> In trials that reported an ext than 1 BP measure, such together nighttime and also daytime ambulatory BP, we provided the average BP calculated native the greatest variety of measurements.

Heterogeneity to be assessed utilizing the Cochran Q statistic, in i beg your pardon a P worth of 2) statistics, with I2> 50% taken into consideration indicative of considerable heterogeneity.<19> us presented the outcomes on the communication of a random-effects design when the test because that heterogeneity that the total population was significant. Otherwise, the outcomes of a fixed-effects design are presented.<20> To recognize the possible source of heterogeneity within the studies, subgroup and also sensitivity analyses were performed in accordance with the Cochrane Handbook for systematic Reviews of Interventions. The complying with information to be abstracted in the subgroup analyses: consumption of catechins, separated into high (≥615 mg/d, high median) and also low (<21> A P value of meta-analysis and ethical approval was no necessary.

3 Results

3.1 outcomes of the literary works search

A complete of 1132 write-ups were initially identified after electronic searching. That them, 1047 posts were excluded because they were no clinical trials, the interventions were irrelevant to the existing meta-analysis, or they were copied articles. Eighty-five short articles remained because that a an ext detailed full-text inspection. Second 61 short articles were excluded for assorted reasons: 26 posts were excluded due to the fact that no pertinent outcomes were reported; 10 posts were excluded due to the fact that green tea extract to be administered as part of a multicomponent supplement; 4 write-ups were excluded because only the summary was available; 18 posts were excluded because they go not fulfill the consists criteria; and 3 posts were excluded since the experiment duration was meta-analysis (Fig. 1).

Figure 1:
Flow chart of the study an option process. From a total of 1132 perhaps relevant studies, 24 randomized managed trials the met the predefined inclusion and exclusion criteria were consisted of in the meta-analysis.

3.2 research characteristics

Twenty-four standard RCTs through 1697 topics were enrolled in the meta-analysis.<22–45> The baseline features of the studies included in the meta-analysis are described in Table 1. The trial dimension ranged from 22 to 240 subjects. The duration of the eco-friendly tea intervention varied indigenous 3 to 16 weeks. The mean age of the trial entrants ranged indigenous 22 to 74 years. The doses of environment-friendly tea catechins in the treatment group ranged indigenous 208 to 1344 mg/d. The mean pretreatment SBP ranged from 111 come 147 mm Hg, and the mean DBP ranged native 68 come 93 mm Hg.

Table 1:
Characteristics of 24 consisted of randomized managed trials.

Of the 24 trials through 25 comparisons contained in the present meta-analysis, 10 comparisons concentrated on adults with normotension<27,28,31,34,36,37,41,43,45> and 15 to compare investigated adults through high-normal or hypertensive BPs.<22–26,29,30,32,33,35,38–40,42,44> Eight comparisons were performed in healthy subjects,<28,34,36,37,41,43,45> and 17 compare were carried out in patients with cardiovascular risks.<22–27,29–33,35,38–40,42,44> most of the to compare (22/25) provided a parallel study design,<22–24,26–29,31–41,43–45> vice versa, 3 comparisons embraced a crossover design.<25,30,42> Eight comparisons selected eco-friendly tea beverage,<22,29,30,38–40,43,45> and also 17 to compare used environment-friendly tea extract capsules.<23–28,31–37,41,42,44> of the consisted of studies, 10 comparisons to be performed in west countries<22–25,27,28,31,41,42,44> and the staying 15 were performed in oriental countries.<26,29,30,32–40,43,45> nine comparisons offered decaffeinated environment-friendly tea extract together supplement,<22,24–26,31,33,35,36,41> 12 comparisons offered caffeinated environment-friendly tea together supplement,<27–30,32,37–40,43,45> and also 4 did not report the usage of caffeinated supplements<23,34,42,44> (Table 1).

3.3 Data quality

The outcomes on the validity of the consisted of trials room presented in Table 2. Twelve trials were classified together high high quality (Jadad score that 4),<23–26,32,33,36,37,41,43,44> and 12 trials were classified as low high quality (Jadad score that 2 or 3).<22,27–31,34,35,38–40,42,45> assignment concealment was sufficient in 11 trials and unclear in 13 trials. Twenty trials had actually a double-blinded RCT design, 1 trial had a single-blinded design, and 3 trials had actually an open-label design. Ten trials report the generation of random numbers, but the various other 14 trials go not. Every trials except for 1 report dropouts and the reasons for the dropouts (Table 2).

Table 2:
Validity of contained studies.

3.4 result of environment-friendly tea on BP

Twenty-five comparisons native 24 studies consisting of 859 topics in the green tea group and 838 topics in the placebo group reported the SBPs and DBPs in ~ baseline and follow-up. Contrasted with the control, eco-friendly tea significantly lowered both SBP (−1.17mm Hg; 95%CI: −2.18 to−0.16; P = .02) (Fig. 2) and DBP (−1.24mm Hg, 95%CI: −2.07 to−0.40; P = .004) (Fig. 3). The pooled impacts on both SBP and also DBP to be heterogeneous (I2 = 43% and also P = .01 for SBP, I2 = 57% and P = .0002 because that DBP); thus, we reported the outcomes from the random-effects models.

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Figure 2:
Net transforms in systolic blood push in randomized trials of green tea supplementation.