Abstract
Prospective cohort studies have described an association between coffee or tea consumption and the risk of developing diabetes. However, whether coffee or tea improves glucose metabolism remains uncertain. We investigated the effect of coffee and tea on glucose metabolism by conducting a systematic review and meta-analysis of randomized controlled trials. Electronic databases were searched for articles published up 19 February 2017. The primary endpoint was the mean difference in post-intervention fasting blood glucose (FBG) levels between the groups. Of 892 citations screened, 27 studies (1898 participants) were included in our meta-analysis. A network meta-analysis suggested that green tea, but not caffeinated/decaffeinated coffee or black tea, may reduce FBG levels, compared with placebo/water (−2.10 mg/dL; 95% confidence interval (CI), −3.96 to −0.24 mg/dL; p = 0.03; moderate quality of evidence). In a subgroup analysis, the effect of green tea on FBG levels was statistically significant only in studies with a mean age of < 55-years-old or Asian-based studies. The oolong tea group also showed a significant decrease in FBG, but the quality of evidence was very low. In conclusion, green tea consumption might decrease FBG levels, especially in < 55-year-olds or Asian-based populations.
Highlights
The number of people with diabetes is increasing rapidly, worldwide
In this systematic review and Network meta-analysis (NMA), we evaluated the effects of various coffee and tea consumptions on glucose metabolism across available randomized controlled trial (RCT) data
As for the secondary endpoint, studies with a moderate quality of evidence indicated that caffeinated coffee consumption may increase insulin concentrations
Summary
The number of people with diabetes is increasing rapidly, worldwide. The International DiabetesFederation reported that in 2015, 415 million adults had diabetes and that by 2040, this number is expected to rise to 642 million [1]. The number of people with diabetes is increasing rapidly, worldwide. Federation reported that in 2015, 415 million adults had diabetes and that by 2040, this number is expected to rise to 642 million [1]. In 2015, the global economic burden associated with diabetes reached US$1.31 trillion, becoming a substantial global economic burden [2]. Low-cost and accessible strategies for preventing diabetes are required. Coffee and tea are widely consumed beverages and their consumption is integrated into people’s daily lives.
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