Heavy exercise, nutrition and immune function: is there a connection?

Exercise participation can modulate interactions between nutritional status and immune function in at least three ways. Athletes and health conscious exercisers may occasionally adopt an unusual diet: megadoses of vitamins, large quantities of protein, carbohydrate or polyunsaturated fat, specific amino acid supplements, or an overall energy deficit. Prolonged exercise may also deplete glycogen reserves, leading to competition between the muscles and immune cells for key amino acids. Finally, an increased intake of antioxidants may protect the active person against an augmented production of reactive species associated with increased tissue metabolism and minor muscle injuries. Despite many potential mechanisms for a disturbance of immune function, most changes in nutritional status are short-lived, and there is little evidence that resistance to infection is reduced, with the possible exceptions of ultraendurance events, chronic overtraining and drastic attempts to reduce body mass.