Effects of tea or tea extract on metabolic profiles in patients with type 2 diabetes mellitus: a meta‐analysis of ten randomized controlled trials

Abstract

As consumption of tea has been confirmed as a protective factor for type 2 diabetes mellitus (T2DM), it would be interesting to know if T2DM patients could benefit from tea. Because of small sample sizes and inconsistent results of previous studies, we performed this meta-analysis to reevaluate the effects of tea or tea extract on all available outcomes in patients with T2DM. We systematically searched electronic databases of PubMed, Cochrane Library and EMBASE to identify randomized controlled trials of tea in T2DM patients up to January 2015. Weight mean differences for the changes in all outcomes were pooled by Review Manager 5.2 (Cochrane Collaboration, Oxford, England). A total of ten trials including 608 subjects were identified. The meta-analysis found that tea could alleviate the decrease of fasting blood insulin [1.30 U/L, 95% CI (0.36, 2.24)], and reduced waist circumference only in more than 8-week intervention [-2.70 cm, 95% CI (-4.72, -0.69)], whereas there were no statistically significant differences with regard to homeostasis model of insulin resistance 0.38 (-0.18, 0.95), fasting blood glucose -0.05 mmol/L (-0.51, 0.40), low density lipoprotein-cholesterol 0.07 mmol/L (-0.15, 0.29), high density lipoprotein-cholesterol 0.01 mmol/L (-0.08, 0.09), body mass index -0.15 kg/m(2) (-0.50, 0.21), SBP 0.35 mmHg (-3.54, 4.24), DBP -1.02 mmHg (-3.53, 1.48), triglycerides -0.11 mmol/L (-0.28, 0.05) and fasting cholesterol -0.05 mmol/L (-0.20, 0.11) in patients with T2DM, and leptin, ADPN, CRE and UA were also non-significant. The intervention of tea or tea extraction could maintain a stable fasting blood insulin and reduce waist circumference in the T2DM patients; however, the effects on other outcomes were not significant. Copyright © 2015 John Wiley & Sons, Ltd.

A Systematic Review and Meta-Analysis of the Effects of Flavanol-Containing Tea, Cocoa and Apple Products on Body Composition and Blood Lipids: Exploring the Factors Responsible for Variability in Their Efficacy

“…Recent meta-analyses (Table S3) [138,139,140,141,142,143,144,145,146,147,148,149,150,151] suggest that the consumption of flavanol-containing tea and tea products could reduce total- and LDL-cholesterol as well as body mass index (BMI) and waist circumference (WC), while chocolate and cocoa flavanols also appear to regulate blood lipid levels. Nonetheless, the results of these analyses are inconsistent, partly due to the large heterogeneity of the clinical trials included.…”

Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity

“…275, 276 Yet, controlled trials of tea have not identified robust benefits on markers of glucose-insulin homeostasis. 277, 278 However, in meta-analyses of trials, green tea, black tea, and herbal roselle tea each modestly lower BP; 279-281 while green and black tea, but not herbal roselle tea, also lower LDL-cholesterol. 282-284 …”

Green Tea Polyphenols Modify the Gut Microbiome in db/db Mice as Co‐Abundance Groups Correlating with the Blood Glucose Lowering Effect

“…In db/db mice, a diabetes model, dietary EGCG was found to prevent the progression of glucose intolerance . Many epidemiological studies and short‐term randomized controlled trials (RCT) also showed an association between tea or catechin consumption and lower incidence of metabolic syndrome and diabetes, even though the results are not conclusive . In most studies, the beneficial effects were observed in individuals consuming three to four cups of tea (or 600–900 mg of tea catechins) or more daily.…”