In a recent review on infectious disease in athletes, it was reported that despite moderate exercise improving immunity, strenuous bouts of prolonged exercise and heavy training impair immune function (Harris, 2011). Moreover, inadequate or inappropriate nutrition can further compound immunocompetence (Gleeson, Nieman & Pedersen, 2004). It is well established that protein deficiency and inadequate intake of iron, zinc and vitamins A, E, B6 and B12 is vital in maintaining healthy immune function (Gleeson, Nieman & Pedersen, 2004). To maintain immune function, the subtle energy requirements of each athlete must be considered. For example, an athlete exercising in a carbohydrate-depleted state experiences larger increases in circulating stress hormones and a greater perturbation of several immune function indices (Gleeson, Nieman & Pedersen, 2004). Hence, the consumption of 30 to 60 grams of carbohydrate during sustained intensive exercise attenuates rises in stress hormones such as cortisol and appears to limit the degree of exercise-induced immune depression (Gleeson, Nieman & Pedersen, 2004). Moreover, there is evidence to suggest that immune-boosting supplements including high doses of glutamine, zinc, probiotics and echinacea, prevent exercise induced immune impairment (Williams, 2006).
Gleeson, M., Nieman, D.C. & Pedersen, B.K. (2004). Exercise, nutrition & immune function. Journal of Sports Sciences, 22, 1, 115-125.
Harris, M.D. (2011). Infectious disease in athletes. Current Sports Medicine Report, 10, 2, 84-89.
Williams, M. (2006). Dietary supplements and sports performance: metabolities, constituents, and extracts. Journal of International Social Sports Nutrition, 13, 3, 1-5.