Oat beta-glucan can counteract the exercise-induced increased risk for upper respiratory tract infection (URTI) in mice, which is at least partly mediated by its effects on lung macrophages. Substantial evidence in humans indicates that carbohydrate-containing sports drinks can offset the decreased immune function associated with stressful exercise. However, no studies in animals or humans have directly examined their effects on URTI using a controlled virus-challenge model. We examined the effects of sucrose feedings alone and in combination with oat beta-glucan on susceptibility to infection and on macrophage antiviral resistance in mice following stressful exercise. These effects were also examined in rested, nonimmunocompromised control mice. Mice were assigned to one of four groups: H(2)O (water), sucrose (S), oat beta-glucan (ObetaG), and sucrose + oat beta-glucan (S+ObetaG). ObetaG and S treatments consisted of a solution of 50% ObetaG and 6% sucrose, respectively, and were administered in drinking water for 10 consecutive days. Exercise consisted of a treadmill run to fatigue performed on three consecutive days. Mice were then intranasally inoculated with a standardized dose of herpes simplex virus 1 (HSV-1) and monitored for morbidity and mortality for 21 days. Additional mice were used to determine macrophage antiviral resistance. In the exercise experiment, S, ObetaG, and S+ObetaG all reduced morbidity (P < 0.05), while only S+ObetaG reduced mortality (P < 0.05). Macrophage antiviral resistance was also increased in S, ObetaG, and S+ObetaG treatments (P < 0.05). In resting controls, S and S+ObetaG reduced morbidity and mortality (P < 0.05) and showed a trend toward increased macrophage antiviral resistance. There was no significant additive effect of S and ObetaG in either control or exercised animals. These data extend our previous work on the benefits of oat beta-glucan to show that sucrose feedings have similar effects on susceptibility to respiratory infection and macrophage antiviral resistance in both resting controls and following exercise stress.
[Show abstract][Hide abstract] ABSTRACT: A large body of literature suggests that certain polysaccharides affect immune system function. Much of this literature, however, consists of in vitro studies or studies in which polysaccharides were injected. Their immunologic effects following oral administration is less clear. The purpose of this systematic review was to consolidate and evaluate the available data regarding the specific immunologic effects of dietary polysaccharides.
Studies were identified by conducting PubMed and Google Scholar electronic searches and through reviews of polysaccharide article bibliographies. Only articles published in English were included in this review. Two researchers reviewed data on study design, control, sample size, results, and nature of outcome measures. Subsequent searches were conducted to gather information about polysaccharide safety, structure and composition, and disposition.
We found 62 publications reporting statistically significant effects of orally ingested glucans, pectins, heteroglycans, glucomannans, fucoidans, galactomannans, arabinogalactans and mixed polysaccharide products in rodents. Fifteen controlled human studies reported that oral glucans, arabinogalactans, heteroglycans, and fucoidans exerted significant effects. Although some studies investigated anti-inflammatory effects, most studies investigated the ability of oral polysaccharides to stimulate the immune system. These studies, as well as safety and toxicity studies, suggest that these polysaccharide products appear to be largely well-tolerated.
Taken as a whole, the oral polysaccharide literature is highly heterogenous and is not sufficient to support broad product structure/function generalizations. Numerous dietary polysaccharides, particularly glucans, appear to elicit diverse immunomodulatory effects in numerous animal tissues, including the blood, GI tract and spleen. Glucan extracts from the Trametes versicolor mushroom improved survival and immune function in human RCTs of cancer patients; glucans, arabinogalactans and fucoidans elicited immunomodulatory effects in controlled studies of healthy adults and patients with canker sores and seasonal allergies. This review provides a foundation that can serve to guide future research on immune modulation by well-characterized polysaccharide compounds.
[Show abstract][Hide abstract] ABSTRACT: Excessive and exhausting physical loads depress the immune system. Carbohydrate consumption may minimize the postexercise suppression of the innate immune system. β-Glucan is a well-known immunomodulator, with positive effects on the functioning of immunocompetent cells. The goal of this study was to determine whether β-glucan dietary supplementation from the mushroom Pleurotus ostreatus decreases the suppressed immune system responses induced by short-term high-intensity exercise in humans. In this double-blind pilot study, 20 elite athletes were randomized to β-glucan (n = 9) or placebo (n = 11) groups; these groups consumed 100 mg of β-glucan (Imunoglukan) or placebo supplements, respectively, once a day for 2 months. Venous whole blood was collected before and after 2 months of supplementation (baseline), both immediately and 1 h after (recovery period) a 20-min intensive exercise bout at the end of the supplementation period. The blood samples were used to measure the cell counts of leukocytes, erythrocyte, and lymphocytes; subpopulations of lymphocytes, granulocytes, and monocytes; and natural killer (NK) cell activity (NKCA). A 28% reduction in NKCA (p < 0.01) below the baseline value was observed in the placebo group during the recovery period, whereas no significant reduction in NKCA was found in the β-glucan group. In addition, no significant decrease in NK cell count was measured in the β-glucan group during the recovery period. Immune cell counts did not differ significantly between the groups. These results indicate that insoluble β-glucan supplementation from P. ostreatus may play a role in modulating exercise-induced changes in NKCA in intensively training athletes.
[Show abstract][Hide abstract] ABSTRACT: The physical training undertaken by athletes is one of a set of lifestyle or behavioural factors that can influence immune function, health and ultimately exercise performance. Others factors including potential exposure to pathogens, health status, lifestyle behaviours, sleep and recovery, nutrition and psychosocial issues, need to be considered alongside the physical demands of an athlete's training programme. The general consensus on managing training to maintain immune health is to start with a programme of low to moderate volume and intensity; employ a gradual and periodised increase in training volumes and loads; add variety to limit training monotony and stress; avoid excessively heavy training loads that could lead to exhaustion, illness or injury; include non-specific cross-training to offset staleness; ensure sufficient rest and recovery; and instigate a testing programme for identifying signs of performance deterioration and manifestations of physical stress. Inter-individual variability in immunocompetence, recovery, exercise capacity, non-training stress factors, and stress tolerance likely explains the different vulnerability of athletes to illness. Most athletes should be able to train with high loads provided their programme includes strategies devised to control the overall strain and stress. Athletes, coaches and medical personnel should be alert to periods of increased risk of illness (e.g. intensive training weeks, the taper period prior to competition, and during competition) and pay particular attention to recovery and nutritional strategies. Although exercising in environmental extremes (heat, cold, altitude) may increase the stress response to acute exercise and elevate the extent of leukocyte trafficking it does not appear to have marked effects on immune function other than a depression of cell-mediated immunity when training at altitude. The available evidence does not support the contention that athletes training and competing in cold (or hot) conditions experience a greater reduction in immune function compared with thermoneutral conditions. Nevertheless, it remains unknown if athletes who regularly train and compete in cold conditions report more frequent, severe or longer-lasting infections. Research should identify whether the airway inflammation associated with breathing large volumes of cold dry air or polluted air impairs airway defences and whether athletes (and their physicians) wrongly interpret the sore throat symptoms that accompany exercising in cold or polluted air as an infection. Elite athletes can benefit from immunonutritional support to bolster immunity during periods of physiological stress. Ensuring adequate energy, carbohydrate and protein intake and avoiding deficiencies of micronutrients are key to maintaining immune health. Evidence is accumulating that some nutritional supplements including flavonoids such as quercetin and Lactobacillus probiotics can augment some aspects of immune function and reduce illness rates in exercise-stressed athletes. Limited data are non-supportive or mixed for use of N-3 polyunsaturated fatty acids, beta-glucans, bovine colostrums, ginseng, echinacea or megadoses of vitamin C by athletes. Relatively short periods of total sleep deprivation in humans (up to 3 consecutive nights without sleep) do not influence the risk of infection, and the reported increase in natural killer cell activity with this duration of total sleep deprivation would seem to rule out the possibility of an "open-window" for respiratory infections. Very little is known about the effects of more prolonged sleep disruption and repeated sleep disturbances on immune function and infection incidence, although recent studies have highlighted the importance of sleep quantity (total duration of sleep per night) and quality (number of awakenings per night) to protect against the common cold in healthy adults. Short- or long-term exercise can activate different components of a physiological stress response. Prolonged intense exercise may induce negative health consequences, many of which may be mediated by physiological pathways activated by chronic stress. Psychological stress is likely additive to the effects of physical stress and whereas short exposures to both physical or psychological stress can have a beneficial effect on immune function, chronic exposure to stress exerts detrimental effects on immune function and health. However, regular moderate exercise could be an important factor in ameliorating the negative health effects of chronic stress via the optimization and maintenance of the survival-promoting physiological changes induced by the short-term or acute stress response. Further research on mechanisms mediating the salubrious effects of exercise, and on the relationship between exercise and the psychosocial stress-status of an individual, is likely to be helpful for more fully and widely harnessing the health benefits of exercise. It is agreed by everyone that prevention of infection is always superior to treatment and this is particularly true in athletes residing in countries with limited medical facilities. Although there is no single method that completely eliminates the risk of contracting an infection, there are several effective ways of reducing the number of infectious episodes incurred over a given period. These means of reducing infection risk include appropriate management of training loads, use of appropriate recovery strategies, good personal hygiene, avoiding contact with large crowds, young children and sick people, good nutrition, getting adequate good quality sleep and limiting other life stresses to a minimum. Part two of the position statement includes sections on: training considerations (David Pyne); nutritional countermeasures to exercise-induced immune perturbations (David Nieman); effects of stress on immune function (Firdaus Dhabhar); sleep disruption and immune function (Roy Shephard); environmental extremes and the immune response to exercise (Neil Walsh and Samuel Oliver) and finally, prevention and treatment of common infections (Stéphane Bermon and Alma Kajeniene).
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