Influence Of Carbohydrate Loading With Different Glycemic Index And Glycemic Load Meal On Immune Responses In Endurance Runners

Purpose: the present study was designed to investigate the influence of 3 days carbohydrate loading with different GI (Glycemic Index) and GL (Glycemic Load) meals on immune responses in endurance runners. Methods: Nine endurance-trained male runners(Age:20.11±0.78 ys; Body mass: 64.8±5.00 kg; BMI: 21±1.31; VO₂max: 64.8±2.35 ml·kg^-1min^-1)completed three main trials in a randomized order separated by at least 7 days. 3 foods which consisted of HH (High Glycemic Index, High Glycemic Load), LL( Low Glycemic Index, LOw Glycemic Load) and HL( High Glycemic Index, Low Glycemic Load) was given to the subjects at 3 days before exercise on a level treadmill(1h of run at 70% VO₂max continuous with 10-km self-pacing run). Carbohydrate intake (% of energy intake), GI, and GL per day was 73%, 80, and 553 for the HH; 73%, 42, and 249 for the LL; 31%, 79, and 227 for the HL. The HH, LL trials provided 10.0g CHO·kg^-1 body mass per day, whereas the HLtrial provided only 3.0g CHO·kg^-1 body mass per day. Then blood glucose concentrations, circulating concentrations of immune cells, serum cortisol concentrations and IL-6 concentrations in the peripheral blood were detected before, during and after exercise.Results:(1) The blood glucose concentrations were higher during and after exercise in the HH and LL trials when compared with the HL trial (P＜0.01). Better performance was found in the LL trial when compared with the HL trial (LL vs HL, 48.6±1.3min vs 55.3±6.9min, P＜0.05), but no statistical differences in time to complete the 10-km self-pacing run between the HH and HL trials (HH vs HL 51.3±5.3min vs 55.3±6.9min, P＞0.05).(2) The immune cell counts were not significant differences during and after exercise between the HH and LL trials (HH vs LL, P＞0.05). Circulating concentrations of Leukocytes were higher during and after exercise in the HL trial when compared with the HH and LL trials (HL vs HH vs LL, P＜0.05 ) . Also, circulating concentrations of lymphocytes were higher during exercise and by post-lh in the HL trial compared with the HH and LL trials, but the significant differences only at 10-km (P＜0.05) Circulating concentrations of neutrophils were lower during and after exercise in the HH and LL trials compared with the HL trial (P＜0.05). But, influence of the meals on the level of moncytes was limited. (3) The percentage of CD4+ cells decreased during exercise (60min: P＜0.01; 10km:P＜0.05) and increased after exercise, but the change of the percentage of CD8⁺ cells was limited. The rate of CD4⁺/CD8⁺ was similar to the change of the CD4⁺ cells. It suggested that the percentage of CD4⁺ cells in the HH and LL trials was higher than that of the HL trial, the same to the rate of CD4⁺/CD8⁺(except 10-km). The rate of CD4⁺/CD8⁺ in the LL trial was normal at post-2 h (LL vs Pre-Ex:P＜0.05).(4) High carbohydrate intake maintained higher blood glucose concentrations during and after exercise and attenuated cortisol concentrations. Serum cortisol concentrations were significantly lower at post-2h in the LL trial(HH vs LL vs HL, P＜0.01) when compared with the HH and HL trials.(5) The concentrations of IL-6 were higher during and after exercise in the HL trial compared with the HH and LL trials (HH vs LL vs HL, P＜0.01 ). The concentrations of IL-6 were not statistical differences during and after exercise between the HH and LL trials (HH vs LL vs HL, P＞0.05).Conclusions: LL trial might improve immune function and prevent immune suppression. It also suggested the blood glucose concentrations were higher during and after exercise in the LL trial, and LL trial attenuated the counts of leukocytes and neutrophils, and the increases of cortisol and IL-6 concentrations compared with the HL trial . Better performance was found in the LL trial. There were no significant differences between two high carbohydrate meals.