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 C-4 [LTC4]-leukotriene E-4 [LTE4] and prostaglandin D-2 [PGD(2)]) and cytokine (interleukin [IL]-1 beta and tumor necrosis factor [TNF]-alpha) concentrations; and (3) eicosanoid metabolites leukotriene B-4 (LTB4) and leukotriene B5 (LTB5) 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, PGD(2), IL-1 beta, 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.