Immunological aspects of sport nutrition

Prolonged bouts of exercise and heavy training regimens are associated with depression of immune system functions that can increase the risk of picking up opportunistic infections such as the common cold and influenza. Some common sport nutrition practices including high-carbohydrate diets and carbohydrate ingestion during exercise, training with low-glycogen stores, intentional dieting for weight loss, ingestion of high-dose antioxidant supplements and protein ingestion post exercise may influence immune system status in athletes. In order to maintain robust immunity, athletes need to consume a well-balanced diet that is sufficient to meet their requirements for energy, carbohydrate, protein and micronutrients. Dietary deficiencies of protein and specific micronutrients are well known to be potential causes of immune dysfunction and an adequate intake of some essential minerals including iron and zinc and the vitamins A, D, E, B6 and B12 are important to maintain a healthy immune function. Vitamin D may be a particular concern as recent studies have emphasised its importance in limiting infection episode incidence and duration in both the general population and in athletes and many individuals exhibit inadequate vitamin D status during the winter months. There is only limited evidence that individual amino acids, β-glucans, herbal extracts and zinc are capable of boosting immunity or reducing infection risk in athletes. The ingestion of carbohydrate during exercise and daily consumption of probiotics, vitamin D3, bovine colostrum and plant polyphenol containing supplements or foodstuffs currently offer the best chance of success, particularly for those individuals who are prone to illness

Acute and chronic effects of exercise on markers of mucosal immunity

Decreased secretion rate of salivary markers of mucosal immunity, and in particular salivary immunoglobulin A (s- IgA), have been implicated as risk factors for subsequent episodes of respiratory infection in athletes. IgA is the predominant Ig in mucosal secretions and acts with innate mucosal defences to provide the ‘first line of defence’ against pathogens and antigens presented at the mucosa. As well as summarising the evidence concerning the effects of acute exercise and longer-term intensive training on these markers of mucosal immunity, this review explores the factors that impact upon salivary responses to exercise, such as method of saliva collection, stimulation of saliva collection and the method of reporting s-IgA data. The influence of adequate hydration and nutritional supplementation during exercise as well as exercising in extreme environmental conditions on salivary responses is also explored. Finally, the possible mechanisms underlying the acute and longer-term of effects of exercise on salivary responses are examined, with particular emphasis on the potential role of the sympathetic nervous system and the expression and mobilisation of the polymeric Ig receptor

Likely additive ergogenic effects of combined pre-exercise dietary nitrate and caffeine ingestion in trained cyclists.

Aims. To evaluate the possible additive effects of beetroot juice plus caffeine on exercise performance. Methods. In a randomized, double-blinded study design, fourteen healthy well-trained men aged 22 ± 3 years performed four trials on different occasions following preexercise ingestion of placebo (PLA), PLA plus 5mg/kg caffeine (PLA+C), beetroot juice providing 8mmol of nitrate (BR), and beetroot juice plus caffeine (BR+C). Participants cycled at 60% maximal oxygen uptake (VO2max) for 30min followed by a time to exhaustion (TTE) trial at 80% VO2max. Saliva was collected before supplement ingestion, before exercise, and after the TTE trial for salivary nitrate, nitrite, and cortisol analysis. Results. In beetroot trials, saliva nitrate and nitrite increased >10-fold before exercise compared with preingestion ( ≤ 0.002). TTE in BR+C was 46% higher than in PLA ( = 0.096) and 18% and 27% nonsignificant TTE improvements were observed on BR+C compared with BR and PLA+C alone, respectively. Lower ratings of perceived exertion during TTE were found during 80% VO2max on BR+C compared with PLA and PLA+C ( < 0.05 for both). Conclusions. Acute preexercise beetroot juice coingestion with caffeine likely has additive effects on exercise performance compared with either beetroot or caffeine alone

The BASES expert statement on exercise, immunity, and infection

An individual's level of physical activity influences their risk of infection, most likely by affecting immune function. Regular moderate exercise reduces the risk of infection compared with a sedentary lifestyle, but very prolonged bouts of exercise and periods of intensified training are associated with an increased risk of infection. There are several lifestyle, nutritional, and training strategies that can be adopted to limit the extent of exercise-induced immunodepression and minimize the risk of infection. This expert statement provides a background summarizing the evidence together with extensive conclusions and practical guidelines

Salivary IgA as a risk factor for upper respiratory infections in elite professional athletes

The relationship between physiological and psychological stress and immune function is widely recognized; however, there is little evidence to confirm a direct link between depressed immune function and incidence of illness in athletes. Purpose: To examine the relationship between salivary immunoglobulin A (s-IgA) and upper respiratory infections (URI) in a cohort of professional athletes over a prolonged period. Methods: Thirty-eight elite America’s Cup yacht racing athletes were studied over 50 wk of training. Resting, unstimulated saliva samples were collected weekly (38 h after exercise, consistent time of day, fasted) together with clinically confirmed URI, training load, and perceived fatigue rating. Results: s-IgA was highly variable within (coefficients of variation [CV] = 48%) and between subjects (CV = 71%). No significant correlation was found between absolute s-IgA concentration and the incidence of URI among athletes (r = 0.11). However, a significant (28%, P G 0.005) reduction in s-IgA occurred during the 3 wk before URI episodes and returned to baseline by 2 wk after a URI. When an athlete did not have, or was not recovering from URI, a s-IgA value lower than 40% of their mean healthy s-IgA concentration indicated a one in two chance of contracting an URI within 3 wk. Conclusion: On a group basis, relative s-IgA determined a substantial proportion of the variability in weekly URI incidence. The typical decline in an individual’s relative s-IgA over the 3 wk before a URI appears to precede and contribute to URI risk, with the magnitude of the decrease related to the risk of URI, independent of the absolute s-IgA concentration. These findings have important implications for athletes and coaches in identifying periods of high URI risk

Effects of Lactobacillus casei Shirota ingestion on common cold infection and herpes virus antibodies in endurance athletes: a placebo-controlled, randomized trial

Aims To assess evidence of health and immune benefit by consumption of a Lactobacillus casei Shirota probiotic in highly physically active people. Methods Single-centre, population-based, randomized, double-blind, placebo-controlled trial. Daily ingestion of probiotic (PRO) or placebo (PLA) for 20 weeks for n = 243 (126 PRO, 117 PLA) university athletes and games players. Subjects completed validated questionnaires on upper respiratory tract infection symptoms (URS) on a daily basis and on physical activity status at weekly intervals during the intervention period. Blood samples were collected before and after 20 weeks of the intervention for determination of Epstein Barr virus (EBV) and cytomegalovirus (CMV) serostatus and antibody levels. Results URS episode incidence was unexpectedly low (mean 0.6 per individual) and was not significantly different on PRO compared with PLA. URS episode duration and severity were also not influenced by PRO. A significant time × group interaction effect was observed for plasma CMV antibody titres in CMV seropositive participants (p < 0.01) with antibody titre falling in the PRO group but remaining unchanged in the PLA group over time. A similar effect was found for plasma EBV antibody titres in EBV seropositive participants (p < 0.01) with antibody titre falling in the PRO group but increasing in the PLA group over time. Conclusions In summary, regular ingestion of PRO did not reduce URS episode incidence which might be attributable to the low URS incidence in this study. Regular ingestion of PRO reduced plasma CMV and EBV antibody titres, an effect that can be interpreted as a benefit to overall immune status

Stimulating whole saliva affects the response of antimicrobial proteins to exercise

Stimulating whole saliva affects the response of antimicrobial proteins to exercis

Effect of acute exercise and hypoxia on markers of systemic and mucosal immunity

Purpose To determine how immune markers are affected by acute hypoxic exercise at the same relative intensity. Methods Twelve endurance-trained males (age: 28 ± 4 years, V˙V˙ O2max: 63.7 ± 5.3 mL/kg/min) cycled for 75 min at 70 % of altitude-specific V˙V˙ O2max, once in normoxia (N) and once in hypobaric hypoxia equivalent to 2000 m above sea-level (H). Blood and saliva samples were collected pre-, post- and 2 h post-exercise. Results Participants cycled at 10.5 % lower power output in H vs. N, with no significant differences in heart rate (P = 0.10) or rating of perceived exertion (P = 0.21). Post-exercise plasma cortisol was higher in H vs. N [683 (95 % CI 576–810) nmol/l vs. 549 (469–643) nmol/l, P = 0.017]. The exercise-induced decrease in CD4:CD8 ratio was greater in H vs. N (−0.5 ± 0.2 vs. −0.3 ± 0.2, P = 0.019). There were no significant between-trial differences for adrenocorticotropic hormone, plasma cytokines, antigen-stimulated cytokine production, salivary immunoglobulin-A or lactoferrin. However, there was a main trial effect for concentration [F(11) = 5.99, P < 0.032] and secretion [F(11) = 5.01, P < 0.047] of salivary lysozyme, with this being higher in N at every time-point. Conclusion Whether the observed differences between H and N are of sufficient magnitude to clinically impair host defence is questionable, particularly as they are transient in nature and since other immune markers are unaffected. As such, acute hypoxic exercise likely does not pose a meaningful additional threat to immune function compared to exercise at sea level, provided that absolute workload is reduced in hypoxia so that relative exercise intensity is the same

Heightened exercise-induced oxidative stress at simulated moderate level altitude vs. sea level in trained cyclists

Altitude exposure can exaggerate the transient increase in markers of oxidative stress observed following acute exercise. However, these responses have not been monitored in endurance-trained cyclists at altitudes typically experienced while training. Endurance trained males (n = 12; mean (± SD) age: 28 ± 4 years, V O 2max 63.7 ± 5.3 ml/kg/min) undertook two 75-min exercise trials at 70% relative V O 2max ; once in normoxia and once in hypobaric hypoxia, equivalent to 2000m above sea level (hypoxia). Blood samples were collected before, immediately after and 2 h postexercise to assess plasma parameters of oxidative stress (protein carbonylation (PC), thiobarbituric acid reactive substances (TBARS), total antioxidant capacity (TAC) and catalase activity (CAT)). Participants cycled at 10.5% lower power output in hypoxia vs. normoxia, with no differences in heart rate, blood lactate or rating of perceived exertion observed. PC increased and decreased immediately after exercise in hypoxia and normoxia respectively (nmol/mg/protein: Normoxia-0.3 ± 0.1, Hypoxia + 0.4 ± 0.1; both p < .05). CAT increased immediately postexercise in both trials, with the magnitude of change greater in hypoxia (nmol/min/ml: Normoxia + 12.0 ± 5.0, Hypoxia + 27.7 ± 4.8; both p < .05). CAT was elevated above baseline values at 2 h postexercise in Hypoxia only (Normoxia + 0.2 ± 2.4, Hypoxia + 18.4 ± 5.2; p < .05). No differences were observed in the changes in TBARS and TAC between hypoxia and normoxia. Trained male cyclists demonstrated a differential pattern/timecourse of changes in markers of oxidative stress following submaximal exercise under hypoxic vs. normoxic conditions

Effects of acute postexercise chocolate milk consumption during intensive judo training on the recovery of salivary hormones, salivary SIgA, mood state, muscle soreness, and judo-related performance

This study examined the effects of postexercise chocolate milk (CM) or water (W) consumption during 5 days of intensive judo training with concomitant weight loss on salivary cortisol and testosterone, salivary secretory immunoglobulin A (SIgA), delayed-onset muscle soreness (DOMS), and judo-related performance. Twelve trained male judo athletes engaged in 5 days of intensive judo training followed by a simulated judo competition, on 2 separate training weeks 14 days apart. The athletes consumed 1000 mL ofW(week 1) or CM (week 2) immediately post-training. During both weeks, athletes were instructed to “make weight” for the upcoming competition. Performance in timed push-ups and the Special Judo Fitness Test improved by 14.6% and 6.8%, respectively, at the end of the training week with CM consumption (both p < 0.001). Decreased salivary cortisol (p < 0.01) and a trend for an increased salivary testosterone/cortisol ratio (p = 0.07) were also observed midweek in the CM condition. Saliva flow rate was higher during the week with CM intake compared withWintake (p < 0.001). DOMS (p < 0.001) and mood disturbance (p < 0.0001) increased after the first day of training in the W condition but not in the CM condition. Salivary testosterone and SIgA responses were similar between treatments (p > 0.05). Body mass decreased by 1.9% in theWcondition and by 1.1% in the CM condition, with no significant difference between treatments. This study indicates that postexercise CM consumption during short-term intensive judo training enhances aspects of recovery without affecting intentional weight loss