Exercise and Immune Function: Nutritional Influences

Data from three randomized studies support the viewpoint that near-daily physical activity reduces the number of days with sickness (Nieman et al., 1990b, 1993, 1998c). In these studies, women in the exercise groups walked briskly 35-45 minutes, five days a week, for 12-15 weeks during the winter/spring or fall, while the control groups remained physically inactive. The results were in the same direction reported by fitness enthusiasts—walkers experienced about half the days with cold symptoms of the sedentary controls (Figure 1). A recent one-year epidemiological study of 547 adults demonstrated a 23% reduction in risk of upper respiratory tract infection (URTI) in those engaging in regular versus irregular moderate-to-vigorous physical activity (Matthews et al., 2000). In healthy elderly subjects, URTI symptomatology during a one-year period was inversely related to energy expended during moderate physical activity (Kostka et al., 2000).