Effect of Green Coffee Extract Combined With Alpha-Lipoic Acid on Blood Glucose Homeostasis in Healthy Adults

Effect of Green Coffee Extract Combined With Alpha-Lipoic Acid on Blood Glucose Homeostasis in Healthy Adults

Green coffee extract (GCE) supplementation has been shown to induce favourable health benefits on glucose metabolism and weight management. Previous literature suggests that the benefits of GCE are due to the high bioavailability of chlorogenic acid (CGA) which is known for its antioxidant and anti-inflammatory properties but is destroyed during the bean roasting process used to make coffee in Western societies. Whilst some studies examining chronic and high dose GCE supplementation (4-12 weeks) report beneficial effects on glucose metabolism and reductions in body mass following supplementation, comparably less is known about the effect of acute (single dose) GCE supplementation. Another natural compound, alpha-lipoic acid (ALA) has antioxidant properties and may also benefit glucose metabolism. The purpose of the current study is to determine the impact of acute supplementation of GCE with ALA on postprandial blood glucose concentration following consumption of a carbohydrate drink in healthy adults. A secondary objective is to evaluate the effect of GCE+ALA on blood insulin concentrations, insulin sensitivity, glucose oxidation, and perceptions of appetite.

The primary purpose of this study is to determine if GCE combined with ALA supplementation influences postprandial glucose metabolism. Participants will complete 3 visits to the investigator's laboratory at the University of Toronto. On each occasion, participants will consume a sugary drink (75g sugar) and investigators will take blood and breath samples for 2 hours. Participants will also be asked to fill out some questionnaires about appetite during this time. Thirty minutes before consuming the sugary drink, participants will consume one of the following pill supplements in a randomized order: 1) 200mg CGE + 200mg ALA; 2) 200mg GCE + 400mg ALA; or 3) Placebo (no CGE or ALA).

The study will advance knowledge regarding the effects of GCE and ALA on postprandial glycemia and insulin sensitivity.

Inclusion Criteria:

• 18-45 years
• BMI 20 - 30 kg/m2
• Weight stable (within ± 2kg for at least 6 months)
• Experiencing monthly menstrual periods (eumenorrheic) if female
• Non-smoker

Exclusion Criteria:

• Previous history of cardiovascular or metabolic disease
• Use of medication for managing blood glucose or lipid metabolism
• Current use of monophasic or biphasic oral contraceptives within the last 3 months (triphasic oral contraceptives are okay)
• Current supplementation of green coffee extract or supplementing in the last 3 months
• Irregular menstrual cycles (<21 days or >35 days)
• Pregnant or lactating
• Recreational smoking of any form (tobacco or cannabis)
• Not willing to consume the 24-hour control diet prior to metabolic trials