Vitamin C supplementation and upper respiratory tract infections in marathon runners

The purpose of this study was to determine whether vitamin C supplementation reduces the incidence of upper respiratory tract infections (URTIs), and attempt to explain the variability in URTIs among marathon runners and sedentary subjects. Marathon runners (n=44) and sedentary subjects (n=48) were randomly assigned either 1,000 mg vitamin C or a placebo daily for two months prior to and one month following a marathon race. Baseline (pre-supplementation) plasma vitamin C concentrations were higher among the vitamin C treated runners (VR, n=30) and placebo treated runners (PR, n=14) (78.5 ±2.7 and 84.0 ±3.6 mmol/L, respectively) compared to vitamin C treated sedentary (VS, n=23) and placebo treated sedentary (PS, n=25) subjects (61.1±4.7 and 52.8 ±5.0 mmol/L, respectively). Vitamin C concentrations increased with supplementation (81.0±2.1 mmol/L for VR and 72.6 ±2.9 mmol/L for VS). No treatment differences were found for URTI incidence respectively). Multiple logistic regression revealed the following factors to be significantly related to an increased risk of URTIs: (1) faster training pace, (2) greater number of marathons run, (3) shorter distance for the longest run of the week, and (4) female gender. The data indicate that vitamin C supplementation of 1,000 mg/day did not decrease the incidence of URTIs in marathon runners. Training and gender were more influential than vitamin C supplementation in explaining the incidence of URTIs. Introduction Exercise is accompanied by hormonal and immunological changes that are associated with psychological stress. Psychological stress has been associated with an increase in susceptibility to the common cold (1,2). Similarly, prolonged exercise results in an increased risk of upper respiratory tract infections (URTIs) (3-5). High intensity, long endurance exercise such as marathon running has been shown to suppress immune function (6). In