Effect of post-exercise caffeine and green coffee bean extract consumption on blood glucose and insulin concentrations

Objective: The aim of this study was to investigate the effects of ingesting caffeine and green coffee bean extract on blood glucose and insulin concentrations during a post-exercise oral glucose tolerance test. Methods: Ten male cyclists (age: 26 +/- 5 y; height: 179.9 +/- 5.4 cm; weight: 77.6 +/- 13.3 kg; body mass index: 24 +/- 4.3 kg/m(2); VO2 peak: 55.9 +/- 8.4 mL.kg.min(-1)) participated in this study. In a randomized order, each participant completed three 30-min bouts of cycling at 60% of peak power output. Immediately after exercise, each participant consumed 75 g of dextrose with either 5 mg/kg body weight of caffeine, 10 mg/kg of green coffee bean extract (5 mg/kg chlorogenic acid), or placebo. Venous blood samples were collected immediately before and after exercise during completion of the oral glucose tolerance test. Results: No significant time x treatment effects for blood glucose and insulin were found. Two-h glucose and insulin area under the curve values, respectively, for the caffeine (658 +/- 74 mmol/L and 30,005 +/- 13,304 pmol/L), green coffee bean extract (637 +/- 100 mmol/L and 31,965 +/- 23,586 pmol/L), and placebo (661 +/- 77 mmol/L and 27,020 +/- 12,339 pmol/L) trials were not significantly different (P > 0.05). Conclusion: Caffeine and green coffee bean extract did not significantly alter postexercise blood glucose and insulin concentrations when compared with a placebo. More human research is needed to determine the impact of these combined nutritional treatments and exercise on changes in blood glucose and insulin. (C) 2015 Elsevier Inc. All rights reserved.