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Review
. 2020 Jul 10:17:56.
doi: 10.1186/s12986-020-00469-5. eCollection 2020.

Effects of green tea consumption on glycemic control: a systematic review and meta-analysis of randomized controlled trials

Renfan Xu  1 , Yang Bai  2 , Ke Yang  2 , Guangzhi Chen  2
Affiliations
Review

Effects of green tea consumption on glycemic control: a systematic review and meta-analysis of randomized controlled trials

Renfan Xu et al. Nutr Metab (Lond). .

Abstract

Background: The results of human clinical trials investigating the effects of green tea on glycemic control are inconsistent.

Methods: We conducted a systematic review and meta-analysis of RCTs that examined the effects of green tea supplementation on glycemic control. A literature search in PubMed, Embase, and Cochrane Library databases for RCTs that investigated the effect of green tea consumption on glycemic control was performed up to February 2020. A random-effects model was used to estimate weighted mean difference (WMD) with 95% confidence intervals (CIs).

Results: Twenty-seven trials involving 2194 subjects were included in the meta-analysis. The pooled results showed that green tea significantly lowered fasting blood glucose by - 1.44 mg/dL (95%CI:-2.26, - 0.62 mg/dL; P < 0.001) with no obvious heterogeneity (I 2 = 7.7%). However, green tea consumption did not significantly affect fasting insulin and HbA1c values. The mean differences were - 0.46μIU/mL (95% CI: - 1.10, 0.17μIU/mL; P = 0.21) for fasting insulin and - 0.06%; (95% CI: - 0.12, 0.01%; P = 0.07) for HbA1c concentrations. Heterogeneity was significant in fasting insulin (I 2 = 46.8%) and mild in HbA1c (I 2 = 1.7%).

Conclusions: In short-term trials, green tea supplementation significantly reduced fasting glucose, but had no significant effect on fasting insulin and HbA1c. Long-term trials assessing the effects of green tea supplementation on glycemic control are needed.

Keywords: Catechin; Glycemic control; Green tea; Meta-analysis.

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Conflict of interest statement

Competing interestsThe authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Flow diagram of the trial selection process
Fig. 2
Fig. 2
Meta-analysis of the effects of green tea on fasting blood glucose concentrations. Results from individual trials were pooled with the use of random-effect models and are expressed as weighted mean differences with 95% CIs
Fig. 3
Fig. 3
Meta-analysis of the effects of green tea on fasting blood insulin concentrations. Results from individual trials were pooled with the use of random-effect models and are expressed as weighted mean differences with 95% CIs
Fig. 4
Fig. 4
Meta-analysis of the effects of green tea on HbAlc concentrations. Results from individual trials were pooled with the use of random-effect models and are expressed as weighted mean differences with 95% CIs
Fig. 5
Fig. 5
a Relation between the WMD of FBG and intervention dose in 27 independent randomized controlled comparisons. b Relation between the WMD of FBI and intervention dose in 18 independent randomized controlled comparisons. c Relation between the WMD of HbAlc and intervention dose in 11 independent randomized controlled comparisons. Each circle represents a study, telescoped by its weight in the analysis. Meta-regression found no linear relations between WMD in FBG (P = 0.89), FBI (P = 0.97), or HbAlc (P = 0.25) and intervention dose
See this image and copyright information in PMC

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