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

Abstract

Studies regarding the influence of green coffee extract (GCE) on blood glucose levels are conflicting. Thus, we sought to conduct a meta‐analysis and systematic review of all available randomized controlled trials (RCTs) to quantify the effects of GCE and CGA intervention on blood glucose and insulin levels. We performed systematic online searches in Scopus, Web of science, and PubMed databases, from inception to July 2019. Data were combined analyzed using a random effects model (Der Simonian‐Laird method) and reported as weighted mean differences (WMD). Ten trials reported the influences of GCE on FBS and insulin and were subsequently entered into the meta‐analysis. Combined results highlighted that FBS was significantly altered after GCE consumption (WMD: −1.791 mg/dl, 95% CI −3.404, −0.177), with no significant heterogeneity among the studies (I2 = 35.0%, p = .128). However, overall results demonstrated that GCE administration did not result in any significant alteration in insulin levels (WMD: −0.925 μU/ml, 95% CI:−1.915, 0.064), with significant heterogeneity found across studies (I2 = 87.9%). In sub‐group analysis, insulin levels were significantly reduced when GCE was supplemented in dosages of ≥400 mg/day (WMD:−1.942 mg/dl, 95% CI:−1.184, −0.975; I2 = 0.0%). The results of present study support the use of GCE for the enhancement of blood glucose, while subgroup analysis highlighted significant improvements in insulin levels when GCE is supplemented in doses ≥400 mg/day.

A Promising Functional Food for Diabetes Prevention, Antioxidation, and Anti-inflammation of Green Coffee Bean Extract

“…The digestive enzyme binding with GCBE is inactivated, reducing blood sugar levels. Therefore, the present results indicate that GCBE is a potential compound to act against hyperglycemia, consistent with results reported in previous studies in vitro, in vivo, and in clinical trials [13,35,37] Macrophages are usually used as a model to study the anti-inflammatory effect of drugs or plant extract because they are the principal immune cells responsible for inflammation of various organs. Macrophages produce cytokines and reactive oxygen species (ROS), producing oxidative stress and increased activation of the inflammation pathway [38].…”

Effects of decaffeinated green coffee extract supplementation on anthropometric indices, blood glucose, leptin, adiponectin and neuropeptide Y (NPY) in breast cancer survivors: a randomized clinical trial

“…Also, the results of the present study are consistent with two meta-analyses and a review [50][51][52] that reported that green coffee extract has no significant effect on insulin and HOMA-IR levels.…”

Insulin-Related Liver Pathways and the Therapeutic Effects of Aerobic Training, Green Coffee, and Chlorogenic Acid Supplementation in Prediabetic Mice

“…We found that while EX caused weight loss in the PD mice, GC and CGA alone had no effect, as we found, others reported that EX promoted weight loss and improvement in body composition. However, there effects of GC and CGA on weight loss are controversial [ 17 , 20 , 31 – 33 ]. It is possible that variation in study design and dosages explain variation in reported outcomes.…”

“…Green coffee (GC) is unroasted, increasing in use, is thought to have antioxidant and antiinflammatory properties, and has been propped as a treatment for certain diseases. Green coffee is rich in phytochemicals such as chlorogenic acid (CA) that is believed to be the main source of its beneficial properties [15][16][17][18].…”