Effects of an acute dose of antioxidants on glucose metabolism at rest, during exercise, and during a glucose load in healthy young subjects: A randomized, placebo-controlled, double- blind crossover trial

Abstract

Abstract Background: Reactive oxygen species (ROS) regulate glucose metabolism (GM) by improving the translocation of GLUT4 in skeletal muscle and pancreatic beta cells in vitro. ROS triggered by exercise promotes GM regulation. Antioxidant supplementation could block these beneficial effects, altering these processes during exercise. However, there is limited evidence in humans on whether antioxidant intake affects GM. Therefore, we investigate the effect that a high dose of antioxidants (HDA) has on GM. Methods: Two trials: 60 minutes before an endurance exercise bout (EEX) and 60 minutes before an oral glucose tolerance test (OGTT), ten healthy and physically active male subjects (age, 25.3 ± 4.2; HOMA-IR, 1.3 ± 0.43; VO2max, 50.6 ± 8.12 mL•kg-1•min-1) consumed a high dose of antioxidants (HDA, 1000 mg of Vitamin C, 600 IU of Vitamin E, and 600 mg of α-lipoic acid) or placebo (2000 mg of talc) before each trial. Trials were 7 days apart and consisted of 1) 60 minutes of endurance exercise at 60 % of Vo2max and 2) 60 minutes of OGTT (75 g). Measurements of gas exchange and capillary blood samples were collected every 15 minutes during both trials. Results: Ingestion of antioxidants (AOC) by the participants in the trial showed higher resting blood glucose than the placebo (AOC, 95.5 ± 7.6; placebo, 87.4 ± 6.4 mg/dl-1; P = 0.03). During endurance exercise (EEX), AOC modified carbohydrate oxidation (CHOox) with respect to time (time, P < 0.001; group, P = 0.11; time x group interaction, P = 0.03), showed no changes in lactate or glucose concentration. During OGTT, AOC trial showed a decrease in blood glucose concentrations with respect to time (time, P = 0.001; group, P = 0.17; time x group interaction, P = 0.06), without changes in blood lactate or CHOox. Conclusion: An acute dose of antioxidants increases the glycemic level at rest and (CHOox) during EEX in healthy subjects.