Influence of carbohydrate status on immune responses before and after endurance exercise

To determine the effect of carbohydrate (CHO)status on immune responses after long-duration exercise, on twooccasions, 10 men completed a glycogen-depleting bout of cycleergometry followed by 48 h of either a high-CHO diet (HiCHO; 8.0 gCHO/kg) or a low-CHO diet (LoCHO; 0.5 g CHO/kg). After the 48 h,subjects completed a 60-min ride at 75% maximalO₂ uptake (EX). Blood samples were taken predepletion, pre-EX, post-EX, and 2 and 24 h post-EX and wereassayed for leukocyte number and function, glucose, glutamine, andcortisol. The glucose responses were significantly higher in the HiCHO(4.62 ± 0.26 mM) vs. the LoCHO (3.19 ± 0.15 mM) condition post-EX, and glutamine was significantly higher in the HiCHO(0.472 ± 0.036 mM) vs. the LoCHO (0.410 ± 0.025 mM)condition throughout. Cortisol levels were significantly greater in theLoCHO (587 ± 50 nM) vs. the HiCHO (515 ± 62 nM) conditionthroughout the trial. Lymphocyte proliferation (phytohemagglutinin) wassignificantly depressed after exercise. However, there was nodifference between conditions, and the depression was not correlatedwith elevations in cortisol. Circulating numbers of leukocytes,neutrophils, lymphocytes, and lymphocyte subsets were significantlygreater in the LoCHO vs. the HiCHO condition at the post-EX and 2 hpost-EX time points. These data indicate that the exercise and dietmanipulation altered the number of circulating leukocytes but did notaffect the decrease in lymphocyte proliferation that occurred afterexercise.