Effect of Dietary Intake on Immune Function in Athletes

Abstract

Athletes are exposed to acute and chronic stress that may lead to suppression of the immune system and increased oxidative species generation. In addition, the tendency to consume fewer calories than expended and to avoid fats may further compromise the immune system and antioxidant mechanisms. The exercise stress is proportional to the intensity and duration of the exercise, relative to the maximal capacity of the athlete. Muscle glycogen depletion compromises exercise performance and it also increases the stress. Glycogen stores can be protected by increased fat oxidation (glycogen sparing). The diets of athletes should be balanced so that total caloric intake equals expenditure, and so that the carbohydrates and fats utilised in exercise are replenished. Many athletes do not meet these criteria and have compromised glycogen or fat stores, have deficits in essential fats, and do not take in sufficient micronutrients to support exercise performance, immune competence and antioxidant defence. Either overtraining or under nutrition may lead to an increased risk of infections. Exercise stress leads to a proportional increase in stress hormone levels and concomitant changes in several aspects of immunity, including the following: high cortisol; neutrophilia; lymphopenia; decreases in granulocyte oxidative burst, nasal mucociliary clearance, natural killer cell activity, lymphocyte proliferation, the delayed-type sensitivity response, the production of cytokines in response to mitogens, and nasal and salivary immunoglobulin A levels; blunted major histocompatibility complex II expression in macrophages; and increases in blood granulocyte and monocyte phagocytosis, and pro- and anti-inflammatory cytokines. In addition to providing fuel for exercise, glycolysis, glutaminlysis, fat oxidation and protein degradation participate in metabolism and synthesis of the immune components. Compromising, or overusing, any of these components may lead to immunosuppression. In some cases, supplementation with micronutrients may facilitate the immune system and compensate for deficits in essential nutrients. In summary, athletes should eat adequate calories and nutrients to balance expenditure of all nutrients. Dietary insufficiencies should be compensated for by supplementation with nutrients, with care not to over compensate. By following these rules, and regulating training to avoid overtraining, the immune system can be maintained to minimise the risk of upper respiratory tract infections.

Effect of spirulina food supplement on blood morphological parameters, biochemical composition and on the immune function of sportsmen

“…Spirulina (Spirulina maxima) was known also in Aztecs medicine. They may be used in higher doses than the homeopathic and lower than pharmacological preparations [29].…”

Dietary Intake of Antioxidant Vitamins in Diets of Amateur Adults Preparing For a Marathon

“…Both shortages and excesses of these components may lead to immunosuppression. In some cases, supplementation with antioxidants may improve the immune system and replenish nutrients (Venkatraman and Pendergast 2002).…”

Differential Expression of Immune Response Genes in Steller Sea Lions (Eumetopias jubatus): An Indicator of Ecosystem Health?

“…Expression of these MHC genes is similarly influenced by environmental change and has the added benefit of reflecting real-time insults. Extensive literature has established relationships between physiologic insults (including environmental contaminants/chemicals, viruses, and nutritional stress) and reduced MHC class II expression (Snyder and Unanue, 1982;Hughes et al, 1996;Dong et al, 1997;Venkatraman and Pendergast, 2002;Schwab et al, 2005). Thus, extension of the genotyping approach, to include quantitative measurement of transcription of individual MHC genes, should provide a timely and relevant measure of altered host immune potential and environmental stress.…”

“…While limited studies have suggested that control of select MHC genes can be differentially regulated through promoter polymorphism (Andersen et al, 1991;Berggren and Seddon, 2005), extensive literature has established relationships between physiologic insults and reduced MHC class II expression (Snyder and Unanue, 1982;Schwab et al, 2005). The rationale for our approach was supported by the demonstration that environmental contaminants/chemicals and nutritional stress can result in suppression of the expression (gene transcription) of select MHC genes (Hughes et al, 1996;Dong et al, 1997;Venkatraman and Pendergast, 2002). The utility of this approach is in its ability to provide a more timely indicator of changes in ecosystem health.…”