The role of anti-oxidants in the prevention of post-race upper respiratory tract infection

Master Thesis


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University of Cape Town

Several epidemiological reports suggest that athletes engaging in marathon-type running events are at increased risk of symptoms of upper respiratory tract infections (URTI). A possible explanation for this increased susceptibility is that during prolonged, strenuous exercise, production of immunosuppressive oxygen free radicals is increased. The purpose of this study therefore was to examine the effect of anti-oxidant vitamin supplementation on the incidence and severity of post-race symptoms of URTI's among athletes competing in a 90-kilometer ultramarathon footrace. A double blind, randomised, placebo controlled study design was employed. Eighty-five subjects were divided into three experimental and three control groups. Each athlete selected a non-running partner with whom they were paired. This non-running control was of a similar age and was a member of the same household or otherwise closely associated with the runner. The experimental and control groups were divided into those ingesting 250 mg/day of ascorbic acid (n = 13 runners, 11 non-running controls), or 4.5 mg/day of beta-carotene (n = 12 runners, 11 non-running controls) or placebo (n = 19 runners and 19 nonrunning controls). All groups commenced supplementation six weeks before the ultramarathon and continued for two weeks after the race. The runners and non-running controls experienced the same incidence of symptoms of upper respiratory tract infections during the study period (50% and 53% respectively) but significantly more runners than non-running controls experienced severe symptoms of upper respiratory tract infections of infective origin (45% and 18% respectively, p < 0.01). Of the runners, 30. 8% on supplemental ascorbic acid, 41. 7% on beta-carotene and 68% on placebo developed symptoms of URTI's. The comparative figures for non-running controls were 45.5%, 45.5% and 63% respectively. All of the non-running controls (100%) and 80% of the athletes who developed severe symptoms of URTIs were on placebo medication. Al though post-race symptoms of URTI 's are common in distance runners, prolonged, strenuous exercise itself is only one of a number of risk factors for symptoms of URTI. However, ingestion of supplemental anti-oxidant in the form of ascorbic acid or beta-carotene for an eight-week period before and after an endurance running event significantly decreases the severity of athletes' symptoms of upper respiratory tract infections.