Abstract
Many studies have investigated the relationship between coffee and diabetes. Evaluation of the current evidence on the effect of coffee intake on diabetes is critical. Therefore, we aimed to investigate the potential association between green coffee extract (GCE) and fasting blood glucose (FBG), insulin and homeostatic model assessment of insulin resistance (HOMA-IR) by pooling together the results from clinical trials. PubMed, Scopus and Google Scholar were searched for experimental studies which have been published up to December 2018. Randomized controlled trials (RCTs) that investigated the effect of GCE supplementation on FBG, insulin and HOMA-IR in adults were included for final analysis. A total of six articles were included in the meta-analysis. Results revealed that GCE supplementation reduced FBG level (SMD: −0.32, 95% CI − 0.59 to − 0.05, P = 0.02) but had no effect on insulin levels (SMD: −0.22, 95% CI −0.53 to 0.09, P = 0.159). Although analysis showed that GCE supplementation cannot change the HOMA-IR status (SMD: −0.30, 95% CI −0.73 to 0.13, P = 0.172), after stratified studies by GCE dosage (< 400 mg/day versus > 400 mg/day) there was a significant decrease in HOMA-IR status in a dose greater than 400 mg. These findings suggest that GCE intake might be associated with FBG improvement.
Highlights
Diabetes mellitus has reached an epidemic level in both developing and developed countries
The purpose of the search strategy in this study was to investigate the effect of GCE on glycemic control and the search keywords included: coffee or green coffee or green coffee extract or chlorogenic acid and fasting plasma glucose or fasting blood glucose or fasting blood sugar or glucose or glucose intolerance postprandial or plasma glucose or blood glucose
Included studies Firstly, the 2257 articles were detected by searching in Scopus, Pubmed and Web of science. 2194 studies were excluded because of being a duplication, an irrelevant study, animal or in vitro study and review study and 33 full text papers were revised of which 27 studies, due to different designs and animal samples, were excluded
Summary
Diabetes mellitus has reached an epidemic level in both developing and developed countries. Due to the pandemic level and macro- and micro-vascular complications caused by diabetes mellitus, it could emerge as a Nikpayam et al Diabetol Metab Syndr (2019) 11:91 of CGAs, and due to this fact green coffee, in the form of unroasted beans, has been more widely considered [8]. Several studies have indicated that GCE supplementation is inversely related to hyperglycemia and insulin resistance [5, 10, 14, 15], In contrast, some studies did not support these outcomes [16, 17]. The objective of this current systematic review and meta-analysis is to investigate the results of human clinical trials assessing the efficacy of GCE as a glucose lowering agent
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