Dietary components with demonstrated effectiveness in decreasing the severity of exercise-induced asthma

Mechanisms and management of exercise-induced asthma in elite athletes

OBJECTIVE AND METHODS

Asthma is often reported by elite athletes, especially endurance athletes. The aim of this article is to review current knowledge of mechanisms and management of exercise-induced asthma (EIA) in adult elite athletes.

RESULTS

The mechanisms underlying EIA is incompletely understood, but the two prevailing hypotheses are the hyper-osmolarity and the thermal hypothesis. Both hypotheses consider inflammation and activation of mast cells as being crucial for the development of EIA, although the assumed mechanisms triggering the inflammatory response differ. Objective testing is of utmost importance in the diagnosis of EIA in elite athletes. Management of EIA can be divided into pharmacologic and non-pharmacologic treatment. The basic principles for the treatment of EIA in elite athletes should be as for any asthmatic individual, including use of inhaled corticosteroids (ICS), β(2)-agonists, and leukotriene antagonists. However, evidence suggests that daily use of β(2)-agonists might lead to the development of tolerance. ICS therapy is, due to its anti-inflammatory effects, the recommended primary therapy for EIA also in elite athletes. All doctors treating individuals with asthma, especially elite athletes, should remain updated on doping aspects of asthma therapy. Non-pharmacologic management of EIA in elite athletes includes physical warm-up, which takes advantage of the refractory period following an attack of EIA, whereas high intake of antioxidants may reduce airway inflammation. Wearing heat masks, specially designed for outdoor winter athletes, might protect against bronchoconstriction triggered by inhalation of cold and dry air.

CONCLUSION

EIA in elite athletes should be managed as in any individual with asthma, but the risk of developing tolerance to bronchodilators as well as doping aspects should always be taken into account.

Modification of blood antioxidant status and lipid profile in response to high-intensity endurance exercise after low doses of omega-3 polyunsaturated fatty acids supplementation in healthy volunteers

We investigated whether endurance exercise might modify the blood antioxidant status and lipid profile after omega-3 fatty acid supplementation. Two groups of healthy, fit males performed 1 h of exercise with a constant work load corresponding to 60% of their individual VO(2 max) and various pedaling rates (45 min-60 rev/min followed by a maximal rate), before and after receiving, over 6 weeks, omega-3 fatty acids in a daily dose of 1.3 g or placebo. The resting concentration of triglycerides decreased after omega-3 fatty acid consumption. In response to endurance exercise, the superoxide dismutase activity markedly decreased in sedentary control subjects. This effect was partially protected by omega-3 fatty acid consumption. Supplementation tended to increase atalase activity in response to exercise, and this activity was significantly higher after 1 h of recovery. We conclude that the beneficial effect of omega-3 fatty acid supplementation during endurance exercise may be due to the activation of the superoxide dismutase and catalase pathways.

Ascorbic acid supplementation attenuates exercise-induced bronchoconstriction in patients with asthma

BACKGROUND

Previous research has shown that diet can modify the bronchoconstrictor response to exercise in asthmatic subjects.

OBJECTIVE

Determine the effect of ascorbic acid supplementation on pulmonary function and several urinary markers of airway inflammation in asthmatic subjects with exercise-induced bronchoconstriction (EIB).

METHODS

Eight asthmatic subjects with documented EIB participated in a randomized, placebo controlled double-blind crossover trial. Subjects entered the study on their usual diet and were placed on either 2 weeks of ascorbic acid supplementation (1500 mg/day) or placebo, followed by a 1-week washout period, before crossing over to the alternative diet. Pre- and post-exercise pulmonary function, asthma symptom scores, fraction of exhaled nitric oxide (FENO), and urinary leukotriene (LT) C4-E4 and 9alpha, 11beta-prostagladin (PG) F2] were assessed at the beginning of the trial (usual diet) and at the end of each treatment period.

RESULTS

The ascorbic acid diet significantly reduced (p < 0.05) the maximum fall in post-exercise FEV1 (-6.4 +/- 2.4%) compared to usual (-14.3 +/- 1.6%) and placebo diet (-12.9 +/- 2.4%). Asthma symptoms scores significantly improved (p<0.05) on the ascorbic acid diet compared to the placebo and usual diet. Post-exercise FENO, LTC4-E4 and 9alpha, 11beta-PGF2 concentration was significantly lower (p<0.05) on the ascorbic acid diet compared to the placebo and usual diet.

CONCLUSION

Ascorbic acid supplementation provides a protective effect against exercise-induced airway narrowing in asthmatic subjects.

Protective effect of fish oil supplementation on exercise-induced bronchoconstriction in asthma

BACKGROUND

Previous research has demonstrated that fish oil supplementation has a protective effect on exercise-induced bronchoconstriction (EIB) in elite athletes, which may be attributed to its antiinflammatory properties. Since EIB in asthma involves proinflammatory mediator release, it is feasible that fish oil supplementation may reduce the severity of EIB in asthmatic subjects.

STUDY OBJECTIVES

To determine the efficacy of fish oil supplementation on severity of EIB in subjects with asthma.

DESIGN

Randomized, double-blind, crossover study.

SETTING

Lung function and exercise testing in a university research laboratory.

PATIENTS AND MEASUREMENTS

Sixteen asthmatic patients with documented EIB entered the study on their normal diet and then received either fish oil capsules containing 3.2 g of eicosapentaenoic acid and 2.0 g of docohexaenoic acid (fish oil diet, n = 8) or placebo capsules (placebo diet, n = 8) daily for 3 weeks. At the beginning of the study (normal diet) and at the end of each treatment phase, the following pre-exercise and postexercise measures were assessed: (1) pulmonary function; (2) induced sputum differential cell count percentage and proinflammatory eicosanoid metabolite (leukotriene C4 [LTC4]-leukotriene E4 [LTE4] and prostaglandin D2 [PGD2]) and cytokine (interleukin [IL]-1beta and tumor necrosis factor [TNF]-alpha) concentrations; and (3) eicosanoid metabolites leukotriene B4 (LTB4) and leukotriene B5 (LTB(5)) generation from activated polymorphonuclear leukocytes (PMNLs).

RESULTS

On the normal and placebo diet, subjects exhibited EIB. However, the fish oil diet improved pulmonary function to below the diagnostic EIB threshold, with a concurrent reduction in bronchodilator use. Induced sputum differential cell count percentage and concentrations of LTC4-LTE4, PGD2, IL-1beta, and TNF-alpha were significantly reduced before and following exercise on the fish oil diet compared to the normal and placebo diets. There was a significant reduction in LTB4 and a significant increase in LTB5 generation from activated PMNLs on the fish oil diet compared to the normal and placebo diets.

CONCLUSION

Our data suggest that fish oil supplementation may represent a potentially beneficial nonpharmacologic intervention for asthmatic subjects with EIB.

Dietary polyunsaturated fatty acids in asthma- and exercise-induced bronchoconstriction

Despite progress that has been made in the treatment of asthma, the prevalence and burden of this disease has continued to increase. While pharmacological treatment of asthma is usually highly effective, medications may have significant side effects or exhibit tachyphylaxis. Alternative therapies for treatment that reduce the dose requirements of pharmacological interventions would be beneficial, and could potentially reduce the public health burden of this disease. Ecological and temporal data suggest that dietary factors may have a role in recent increases in the prevalence of asthma. A possible contributing factor to the increased incidence of asthma in Western societies may be the consumption of a proinflammatory diet. In the typical Western diet, 20- to 25-fold more omega (n)-6 polyunsaturated fatty acids (PUFA) than n-3 PUFA are consumed, which promotes the release of proinflammatory arachidonic acid metabolites (leukotrienes and prostanoids). This review will analyze the evidence for the health effects of n-3 PUFA in asthma- and exercise-induced bronchoconstriction (EIB). While clinical data evaluating the effect of omega-3 fatty acid supplementation in asthma has been equivocal, it has recently been shown that fish oil supplementation, rich in n-3 PUFA, reduces airway narrowing, medication use, and proinflammatory mediator generation in nonatopic elite athletes with EIB. These findings are provocative and suggest that dietary fish oil supplementation may be a viable treatment modality and/or adjunct therapy in asthma and EIB.

Asthma, airway inflammation and treatment in elite athletes

Highly trained athletes are repeatedly and strongly exposed to cold air during winter training and to many inhalant irritants and allergens all year round. Asthma occurs most commonly in athletes engaging in endurance events such as cross-country skiing, swimming, or long-distance running. As well as the type of training, a major risk factor is atopic disposition. A mixed type of eosinophilic and neutrophilic airway inflammation has been shown to affect elite swimmers, ice-hockey players, and cross-country skiers. The inflammation may represent a form of repeated thermal, mechanical, or osmotic airway trauma resulting in a healing or remodelling process. Elite athletes commonly use antiasthma drugs to treat exercise-induced bronchial symptoms. Only a few controlled studies have been conducted on the effects of antiasthma drugs on asthma symptoms, bronchial hyperresponsiveness and airway inflammation in elite athletes. Inhaled beta(2)-adrenoceptor agonists are effective against exercise-induced bronchospasm. In contrast, airway inflammation, bronchial hyperresponsiveness and symptoms have responded poorly to inhaled corticosteroids and leukotriene antagonists. As discontinuing high-level exercise has proved effective in reducing eosinophilic airway inflammation, exercise or training should be restricted in athletes having troublesome symptoms and sputum eosinophilia. Switching training to less irritating environments should be considered whenever possible. It appears to be difficult to change the 'natural course' of asthma in athletes by anti-inflammatory treatment.

Effect of lycopene supplementation on lung function after exercise in young athletes who complain of exercise-induced bronchoconstriction symptoms

BACKGROUND

It has been suggested that exercise-induced bronchoconstriction may involve oxidative stress. Strenuous exercise promotes free radical production, which can lead to many of the pathophysiologic changes associated with asthma, including bronchoconstriction, mucus secretion, and microvascular leakage. Lycopene has been shown to have high antioxidative activity.

OBJECTIVE

To evaluate the effect of lycopene supplementation on airway hyperreactivity and inflammation in young athletes who complain of difficulty in breathing related to physical exertion.

METHODS

Nineteen young athletes with exercise-related difficulty in breathing visited the exercise laboratory 3 times. During the first visit, participants underwent a baseline evaluation of exercise-induced bronchoconstriction. Daily for 1 week before each of the 2 subsequent visits, participants ingested 30 mg of lycopene (a natural antioxidant) or placebo (in randomized order, double-blind). A 2-week washout period was given between each visit. During each visit, lung functions were evaluated before and after an 8-minute run on the treadmill (85% of the predicted maximal heart rate).

RESULTS

There was no difference in the mean+/-SD decrease in forced expiratory volume in 1 second after exercise during lycopene treatment compared with placebo treatment (11.8%+/-12.5% and 11.0%+/-11.6%). In addition, there was no apparent division into responders and nonresponders.

CONCLUSION

A daily dose of lycopene for 1 week does not affect lung function after exercise and may not provide any protective effect against clinical difficulty in breathing in young athletes.

Omega-3 Fatty acids and airway hyperresponsiveness in asthma

Despite the progress that has been made in the treatment of asthma, the prevalence and burden of this disease has continued to increase. Exercise is a powerful trigger of asthma symptoms and reversible airflow obstruction and may result in the avoidance of physical activity by patients with asthma, resulting in detrimental consequences to their health. Approximately 90% of patients with asthma are hyperresponsive to exercise and experience exercise-induced bronchoconstriction (EIB). While pharmacologic treatment of asthma is usually highly effective, medications often have significant side-effects or exhibit tachyphylaxis. Alternative therapies for treatment (complementary medicine) that reduce the dose requirements of pharmacologic interventions would be beneficial, and could potentially reduce the public health burden of this disease. There is accumulating evidence that dietary modification has potential to influence the severity of asthma and reduce the prevalence and incidence of this condition. A possible contributing factor to the increased incidence of asthma in Western societies may be the consumption of a proinflammatory diet. In the typical Western diet, 20- to 25-fold more omega- 6 polyunsaturated fatty acids (PUFA) than omega-3 PUFA are consumed, which causes the release of proinflammatory arachidonic acid metabolites (leukotrienes and prostanoids). This review analyzes the existing literature on omega-3 PUFA supplementation as a potential modifier of airway hyperresponsiveness in asthma and includes studies concerning the efficacy of omega-3 PUFA supplementation in EIB. While clinical data evaluating the effect of omega-3 PUFA supplementation in asthma has been equivocal, it has recently been shown that pharmaceutical-grade fish oil (omega-3 PUFA) supplementation reduces airway hyperresponsiveness after exercise, medication use, and proinflammatory mediator generation in nonatopic elite athletes with EIB. These findings are provocative and suggest that dietary omega-3 PUFA supplementation may be a viable treatment modality and/or adjunct therapy in airway hyperresponsiveness. Further studies are needed to confirm these results and understand their mechanism of action.