Effects of green coffee extract on fasting blood glucose, insulin concentration and homeostatic model assessment of insulin resistance (HOMA-IR): a systematic review and meta-analysis of interventional studies

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.

The influence of green coffee bean extract supplementation on blood glucose levels: A systematic review and dose–response meta‐analysis of randomized controlled trials

“…Several studies have shown GCE supplementation decreased blood glucose and insulin concentrations (Roshan et al, 2018;Soga et al, 2013), while contrastingly, an equivalent number of trials did not support such assertions (Fukagawa et al, 2017;Watanabe et al, 2006). Moreover, previously published reviews have few studies and did not evaluate the effects of CGA and GCE supplementation on blood glucose and insulin levels in a dose-response model (Faraji, 2018;Nikpayam et al, 2019). Thus, our aim was to perform a doseresponse meta-analysis and systematic review of all published RCTs to quantify the effects of CGA and GCE supplementation on blood glucose and insulin levels In accord with the aforementioned aim, overall results specified that GCE did not result in any significant alteration in IN; however, subgroup analysis highlighted that IN was significantly reduced when GCE was supplemented in dosages ≥400 mg/day.…”

Effects of Polyphenols on Insulin Resistance

“…A trial for 8 weeks of up to 5 cups of coffee per day found no changes in insulin or glucose markers [ 87 ]. In a systematic review including six studies, green coffee extract lowered fasting blood glucose, but only higher doses were effective at improving HOMA-IR [ 88 ]. Phenolic compounds found in olive leaf, oleuropein and hydroxytyrosol, improved both the action of insulin and secretion from pancreatic β-cells following a 12-week supplementation in middle aged overweight men [ 89 ].…”

Anti-obesity effects of individual or combination treatment with Spirulina platensis and green coffee bean aqueous extracts in high-fat diet-induced obese rats

“…The raw green coffee beans are rich in caffeine, chlorogenic acid, and its related metabolites, such as quinic acid, caffeic acid, and p-coumaric acid (Hasegawa and Mori 2000;Zheng et al 2004;Lopez-Garcia et al 2006). Moreover, recent clinical trials showed promising therapeutic effects of green coffee for improvement lipid and hormonal profiles in obese humans (Gorji et al 2019;Nikpayam et al 2019) and mice (Choi et al 2016).…”