Carbohydrate supplementation does not blunt the prolonged exercise-induced reduction of in vivo immunity

Background Carbohydrate (CHO) supplementation during prolonged exercise is widely acknowledged to blunt in vitro immunoendocrine responses, but no study has investigated in vivo immunity. Purpose To determine the effect of CHO supplementation during prolonged exercise on in vivo immune induction using experimental contact hypersensitivity with the novel antigen diphenylcyclopropenone (DPCP). Methods In a double-blind design, 32 subjects were randomly assigned to 120 min of treadmill exercise at 60 % (V) over dotO(2)max with CHO (Ex-CHO) or placebo (Ex-PLA) supplementation. Responses were also compared to 16 resting control (CON) subjects from a previous study (for additional comparison with a resting non-exercise condition). Standardised diets (24 h pre-trial) and breakfasts (3.5 h pre-trial) were provided. Subjects received a primary DPCP exposure (sensitisation) 20 min after trial completion, and exactly 28 days later the strength of immune reactivity was quantified by magnitude of the cutaneous response (skin-fold thickness and erythema) to a low dose-series DPCP challenge. Stress hormones and leucocyte trafficking were also monitored. Results CHO supplementation blunted the cortisol and leucocyte trafficking responses, but there was no difference (P > 0.05) between Ex-CHO and Ex-PLA in the in vivo immune responses (e.g. both similar to 46 % lower than CON for skin-fold response). Conclusions CHO supplementation does not influence the decrease in in vivo immunity seen after prolonged exercise. The effects with more stressful (or fasted) exercise remain to be determined. However, there appears to be no benefit under the conditions of the present study, which have practical relevance to what many athletes do in training or competition.