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

- Participants performed three 30-min bouts of cycling exercise on different days.
- Oral glucose tolerance tests were conducted after each exercise bout.
- Caffeine was consumed before the oral glucose tolerance test during one trial.
- Green coffee bean extract and a placebo were consumed during the other two trials.
- There were no statistically significant treatment effects.

ObjectiveThe 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.MethodsTen 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/m2; 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.ResultsNo significant time × 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).ConclusionCaffeine 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.