Influence Of Carbohydrate Loading With Different Glycemic Index On Metabolic And Immune Response Of Endurance Exercise

Purpose:Consumption of carbohydrate(CHO) food or beverage before, during,and after prolonged intensive exercise has been shown to reduce the exercise-induced physical stress to immune system.However,little research,if any,has been undertaken to investigate the role of glycemic index(GI) of a pre-exercise sports drink on the metabolic and immune response.Therefore,the purpose of the current study was to examine the effect of sports drinks with different GI on the metabolic and immune response.It was hypothesized that compared with high GI(HGI) sports drink with equal amount of CHO,consumption of low GI(LGI) sports drink before endurance exercise would be beneficial to the metabolic response and resulted in a maintenance of immune function during exercise and recovery.Method:Ten male healthy adults was recruited in this study.120 minutes before the cycling and after an overnight fast,each subject randomly consumed one of the following beverages:HGI(GI=83),LGI(GI=40) or placebo(water,GI=0).The two CHO containing beverages were isocaloric and were intaken by each subject for 1.5 g/kg body mass.Each trial consisted of a cycling at 70%VO2max for 60 minutes on a bicycle ergometer and followed by recovery for 120 minutes.Physiological, biochemical,hormonal and immune responses were measured throughout the experimental period and in the next morning.Result:(1) LGI sports drink consumption minimized the postpradial response of glucose and insulin in serum compared with HGI sports drink. (2) Both of the CHO beverages increased the postpradial concentration of blood lactate acid in spite of their GI values.(3) Pre-exercise LGI loading maintained higher concentration of glucose in serum during the exercise and the recovery within 120 minutes compared with HGI trial. (4) Pre-exercise HGI loading increased the total rate of CHO oxidation during exercise campared with placebo.(5) Pre-exercise LGI loading attenuated the exercise-induced enhancement of leucocytes,neutrophils, monocytes and the ratio of neutrophils/lymphocytes in peripheral circulation campared with HGI trial.(6) Other measured markers, including stress hormones(cortisol,adrenocorticotropic hormone, growth hormone) in serum,lymphocyte subsets(T cells,B cells and NK cells) in peripheral circulation,cytokines(interleukin-1β,tumor necrosis factorαand interleukin-10) and glutamine in serum,seemed to be not effective to estimate the role of GI of the sports drinks in current study.Conclusion:(1) Pre-exercise LGI sports drink consumption was a valuable style of CHO supplementation.(2) Although the effect of pre-exercise CHO consumption on immune response was relatively small, LGI sports drink showed beneficial effects on exercise-induced immune changes.