Effects of tea consumption on metabolic syndrome: A systematic review and meta‐analysis of randomized clinical trials

Abstract

The metabolic syndrome (MetS) is one of the major health hazards and an epidemic worldwide. There is no known best remedy has been defined yet. In the current investigation, we designed a meta-analysis of randomized clinical trials (RCTs) to evaluate the beneficial effects of tea consumption in alleviating metabolic syndromes. Herein, we accumulated the relevant literature available on PubMed and EMBASE databases from January, 2000 to August, 2019. RCTs bearing impact factor of at least 1 or more were studied for the effect of tea consumption on MetS. This metaanalysis suggested that tea consumption has beneficial effects on diastolic blood pressure (DBP), and this finding was characterized of all types of tea in the current study and also for body mass index (BMI) value. Furthermore, this analysis also found that black tea consumption has protective effects on systolic SBP, green tea reduces the incidence of diabetes and lower the level of low-density lipoprotein (LDL) cholesterol. These functions required BMI value at least 28 or higher. The meta data led us to conclude that tea consumption have protective effects on MetS, however, different types of tea might have different protective mechanisms on MetS, but, exact mechanisms are not yet clear and needs to be explored.

Polyphenol-Rich and Alcoholic Beverages and Metabolic Status in Adults Living in Sicily, Southern Italy

“…Regarding the null results on diabetes, we may hypothesize that doses of coffee might not be sufficient to reduce the risk as reported in the scientific literature, or unmeasured confounding factors (i.e., the use of sugar in coffee) might counteract its beneficial effects on insulin sensitivity and glucose homeostasis. Regarding tea, summary of evidence showed it does not appear to significantly affect blood pressure or lipids in short-term [49], while data on metabolic outcomes are mixed and seems to potentially depend on type of tea and doses (i.e., associations observed for higher intake than those reported in our study, which may explain lack of significant findings) [16,50].…”

Tea intake and cardiovascular disease: an umbrella review

“…Xu et al found a significant decrease in total cholesterol among normal weight, overweight, and obese individuals (combined) who consumed green tea vs. placebo (weighted mean difference [WMD]: −4.66 mg/dL; 95% CI: 6.36 to −2.96; p = .0001) in a random effects meta-analysis [ 31 ]. The remaining nine older systematic reviews found no significant effects on total cholesterol across various populations [ 3 , 11 , 18 , 19 , 22 , 27 , 30 , 34 , 49 ], which may be due to a smaller number of studies and overall sample size. The quality of these systematic reviews was judged to be low to high ( Table 2 ).…”

“…No effects were reported for black tea vs. placebo [ 24 ]. Liu et al found a significant decrease in LDL cholesterol among individuals with metabolic syndrome who consumed green and black tea (combined) vs. placebo in a random effects meta-analysis (SMD: −0.63 mmol/L; 95% CI: −1.06 to −0.20; p = .0057) [ 30 ]. Xu et al found a significant decrease in LDL cholesterol among normal weight, overweight, and obese individuals (combined) who consumed green tea vs. placebo (WMD: −4.55 mg/dL; 95% CI: −6.31 to −2.80 mg/dL; p = .0001) in a random effects meta-analysis [ 31 ].…”

“…Twelve systematic reviews assessing effects of tea consumption on high-density lipoprotein (HDL) cholesterol were identified from our literature search [ 3 , 11 , 18 , 19 , 22 , 24 , 26 , 27 , 30 , 31 , 34 , 49 ]. Study populations ranged from healthy individuals and the general adult population to individuals with high CVD risk, hypercholesterolaemia, type-2 diabetes, prediabetes, obesity with metabolic syndrome, or hypertension.…”

“…One study included some adolescents [ 22 ]. These systematic reviews consistently failed to show significant effects on HDL cholesterol across various populations [ 3 , 11 , 18 , 19 , 22 , 24 , 26 , 27 , 30 , 31 , 34 , 49 ]. The quality of these systematic reviews was judged to be critically low to high ( Table 2 ).…”