Green Coffee Extract With Alpha-Lipoic Acid or Dihydroberberine Does Not Improve the Postprandial Glucose Response in Healthy Adults

Abstract

Background: Chronic supplementation (>2 weeks) with green coffee extract (GCE), alpha-lipoic acid (ALA), and dihydroberberine (DHB) results in favourable effects on blood glucose regulation. However, the effect of acute ingestion of these compounds on blood glucose regulation is not well understood. Purpose: The aim of this thesis was to investigate the acute effects of GCE + ALA/DHB supplementation on glucose homeostasis in healthy young adults. Hypothesis: We hypothesized that compared to placebo, ingestion of GCE + ALA 30 min prior to an oral glucose challenge would 1) lower the 2 h glucose incremental area under the curve (auk); 2) lower the 2 h insulin iAUC; 3) increase insulin sensitivity; 4) increase the rates of glucose oxidation; and 5) lower appetite perceptions. We also hypothesized that GCE + ALA ingestion at a higher dose (400 mg) would exert similar or greater effects than GCE + DHB compared to a lower dose (200 mg). Twenty participants completed a double-blind randomized controlled trial involving four metabolic trials separated by a minimum of 4 days. Methods: In each trial, participants consumed one of four supplements- 1) placebo; 2) 200 mg GCE + 200 mg ALA; 3) 200 mg GCE + 400 mg ALA; or 4) 200 mg GCE + 200 mg DHB- 30 min prior to a 75 g oral glucose tolerance test. Results: There was no significant effect of supplementation on glucose iAUC, insulin iAUC, insulin sensitivity, or appetite perceptions. There was a significant effect of supplementation on the iAUC of exogenous glucose oxidation (p = 0.0006), with both the 200 mg GCE + 200 mg ALA and 200 mg GCE + 400 mg ALA groups demonstrating greater glucose oxidation compared to placebo. Conclusion: These findings suggest that although acute supplementation of GCE and ALA in combination does not affect plasma glucose or insulin concentrations, they may have a role in regulating postprandial glucose oxidation.