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Abstract
Several studies have found an increase in upper respiratory tract infections (URTIs) among distance runners (Nieman et al. 1990, Peters et al. 1983). Nieman et al. (1990) reported that marathon runners with higher training mileage had a two-fold increase in URTIs. Peters et al. (1993) found that vitamin C supplements reduced the incidence of URTIs among ultra-marathoners.
The hypothesis of the present study was that vitamin C supplementation does not affect the risk of URTIs among marathon runners. Marathon runners (n = 44) and sedentary subjects (n = 48) were randomly assigned either 1000 mg Vitamin C or a placebo daily for two months prior and one month following the 1994 Duke City Marathon.
Baseline plasma vitamin C concentrations were higher among the runners compared to sedentary subjects $(1.38\pm.05$ and $1.48\pm.06$ mg/dL for vitamin C and placebo-treated runners and $1.08\pm.08$ and $0.93\pm.09$ mg/dL for vitamin C and placebo-treated sedentary subjects). Vitamin C concentrations increased with supplementation, however the increase was more marked among the sedentary subjects $(1.43\pm.04$ mg/dL for runners and $1.28\pm.05$ mg/dL for sedentary subjects following two months of supplementation).
Although no treatment differences were found in URTI incidence for the 3 month period, vitamin C-treated runners tended to have fewer colds during the two week period following the marathon compared to placebo-treated runners (10.0% versus 28.6%).
Using multiple logistic regression, the following factors were related to risk of URTIs: (1) faster training pace, (2) greater number of marathons run, (3) running a shorter distance on the longest run of the week, and (4) female gender. Running mileage and stress levels were not related to risk of URTIs.
Vitamin C supplementation had no apparent effect on lymphocyte proliferation.
