Efficacy And Safety Of Tea And Tea Extract To Improve The Components Of Metabolic Syndrome: A Meta-analysis

【Background】Metabolic syndrome(MS) is a combination of a series of related risk factors of metabolic abnormalities, including central obesity, hyperglycemia(sugar regulation damaged or type 2 diabetes mellitus), dyslipidemia and hypertension and so on. This is a group of life-threatening syndrome and caused serious harm to the health of human beings. In the recent 20 years,with the development of the quality of daily life, the change of the way of diet, and the amount of the ages in China, the incidence of MS is soaring. According to the epidemiological investigation, the incidence of MS in adults is 13.3% in 1992, while which is up to 16.5% in the early 2000. However, the latest data show that the incidence of MS is as high as 24% in 2013. Thus, there is no doubt that MS has become a new chronic metabolic disorder and public health issue that requires much more attention and strict control.At present, improve the metabolic status of patients with MS with measures include to improve the way of life, reduce and optimize the energy intake, increase physical activity, medication and surgery. Among them, the change of dietary structure is the most basic and economic adjustment way of life. The tea culture is rooted in China, and widely disseminated throughout the world, has a long history. As a natural green drinks, tea and tea extract has been reported in many studies in foreign countries with the care and treatment effect on various diseases. However, whether tea or tea extract is benefit for the component of MS including hypertension, diabetes and obesity is unclear. Therefore, the current project aims to collect research reported data by the method of meta-analysis and systematically evaluate the efficiency and safety of tea extract(TE) on improving the MS, in order to provide objective and powerful evidence for nutrition diagnosis and treatment effect of TE on MS.【Objective】To systematically evaluate the efficiency and safety of the green tea, black tea, oolong tea and tea extract in patients with MS on 15 indicators for anthropometric and biochemistry outcomes, cholesterol metabolism, and blood pressure.【Method】Through strict experimental design, reasonable the inclusion and exclusion criteria, two researchers independently searching five international authoritative database, including Pub Med(1980~2014), Psyc INFO(1980~2014), Scopus(1980~2014), EMBase(1980~2014) and The Cochrane Library using the search strategy:(tea(extract) OR green tea(extract) OR black tea(extract) OR oolong tea(extract)) AN D(obesity OR metabolic syndrome). Randomized controlled trial(RC T) or controlled clinical trial of tea extract versus placebo in the treatment of MS were conducted. Meta-analysis was done by using Rev Man 5.2.2 software. The results were summarized using odds ratio(OR) and 95% confidence interval(CI) as a assemble variables.【Results】1. The Meta-analysis included a total of 16 qualified RCT, in which 16 studies focus on green tea(or extract), and 4 on black tea(or extract). A total of 1090 subjects in 16 studies were involved, in which 451 subjects receiving a daily drink of green tea(or extract) or capsules, which 138 subjects receiving a daily drink o f black tea(or extract) or capsules, and which 446 subjects receiving a daily drink o f equivalent dose of placebo beverage or capsule.2. Anthropometric outcomes: Benefits were revealed on reduction of body weight(SMD,-0.21; 95% CI,-0.33 to-0.09, P=0.0007), waist circumference(SMD,-0.24; 95% CI,-0.38 to-0.09, P=0.001) and Body Mass Index(BMI)(SMD,-0.27; 95% CI,-0.40 to-0.15, P<0.0001). No significant difference was found betwee n two groups both in waist-to-hip ratio and hip circumference.3. Cholesterol metabolism outcomes: Benefits were revealed on reduction of the level of low density lipoprotein cholesterol(LDL-C)(SMD,-0.31; 95% CI,-0.55 to-0.06, P=0.01) and increase the level of high density lipoprotein cholesterol(HDL-C)(SMD, 0.18; 95% CI, 0.01 to 0.35, P=0.03). No significant difference was found betwee n two groups both in cholesterol and triglycerides.4. Glycometabolism outcomes: Benefits were revealed on reduction of fasting blood glucose(SMD,-0.22; 95% CI,-0.34 to-0.10, P=0.0003). No significant difference was found between two groups all in HOME-IR, insulin and Hb A1 c.5. Blood pressure: No significant difference was found betwee n two groups both in ms SBP and ms DBP.6. Safety outcomes: All- cause adverse events were minimal between two groups(O R, 0.99; 95% CI: 0.55, 1.77, P = 0.97).【Conclusion】1. TE significantly reduces the level of body weight, waist circumference, and BMI in patients with MS.2. TE significantly reduces the level of serum LDL-C and increases the level of HDL-C.3. TE significantly reduces fasting blood glucose, but plays no role on the level of insulin, HbA1 c, and HOME-IR in patients with MS.4. TE plays no role on improving blood pressure in patients with MS.5. There were no serious adverse events between TE and placebo group.