23 Jan No Benefit of Omega-3 acid Supplements for Exercise-Induced Bronchoconstriction in Asthma
Medical Research: What is the background for this study?
Response: The use of omega-3 acid supplements as treatments for allergic diseases including asthma is controversial. Studies by investigators from Indiana University in the USA have repeatedly demonstrated a beneficial effect of high dose omega-3 fatty acid supplements over 3 weeks in attenuating exercise-induced bronchoconstriction (EIB) similar or possibly better in potency to what may be expected with a regular inhaled corticosteroids. The study by Brannan et al. attempted to validate these findings by using inhaled mannitol, a bronchial provocation test that was derived from the understanding of exercise-induced bronchoconstriction and which has demonstrated experimentally to be a useful model for exercise-induced bronchoconstriction. All pharmacotherapies that modify exercise-induced bronchoconstriction can modify the airway sensitivity to inhaled mannitol in persons with asthma, thus it was of interest to see if an ‘alternative’ treatment that demonstrated efficacy in exercise-induced bronchoconstriction could too modify the airway response to mannitol.
Medical Research: What are the main findings?
Response: The main findings were, to our surprise, there was no benefit of high dose omega-3 fatty acid supplements on bronchial hyperresponsiveness to mannitol over 3 weeks. This was associated with no changes in airway inflammation (sputum eosinophils), lung function or asthma symptom control. We also found no benefit on resting urinary mast cell metabolites, in contrast to the findings in studies showing a benefit of omega-3 fatty acids on EIB. Our findings suggest that omega-3 supplements in tissues may not be able to penetrate tissue and/or modify the substrate flow of eicosanoids in tissue such as the airways of the asthmatic. We did observed the expected reductions in blood triglycerides which suggests that these doses of omega-3s can modify metabolism in the blood or to some extent tissues that are highly perfused.
Medical Research: What should clinicians and patients take away from your report?
Response: This prospective randomised placebo-controlled study demonstrated no efficacy of omega-3 fatty acid supplements on bronchial hyperresponsiveness and airway inflammation in persons with active symptomatic asthma and who were either taking regular inhaled corticosteroids, or beta2 agonists alone, for management of their asthma symptoms. Further, the lack of efficacy on airway sensitivity to mannitol adds doubt to the usefulness of this therapy on attenuating EIB when either used alone or in combination with regular inhaled corticosteroids. In addition, as inhaled mannitol is a standardised bronchial provocation test used to identify the presence of active asthma, in those that have a positive mannitol test it would be clear that omega-3 supplements would have no benefit in treating their asthma.
Medical Research: What recommendations do you have for future research as a result of this study?
Response: The current studies by the Indiana University group using both exercise and eucapnic voluntary hyperpnea (like mannitol, another surrogate test to identify EIB) should be validated by other groups. These studies used either very mild exercise-induced bronchoconstriction or possibly a sub-optimal stimulus to provoke EIB. Studies evaluating drugs in EIB require a standardised optimal exercise stimulus as well as participants with significant and reproducible exercise-induced bronchoconstriction. This would aid in confirming this negative finding. It should be noted that recently negative findings on the effects of omega-3s in relation to cardioprotective effects have surfaced to raise doubt on the effects of omega-3 fatty acids as a treatment in cardiovascular disease, sustaining the controversy but suggesting the beneficial effects of omega-3s may not be as significant as initially proposed.
John D. Brannan, PhD; Johan Bood, PhD; Ahmad Alkhabaz, MD; David Balgoma, PhD; Joceline Otis, BSc; Ingrid Delin, BSc; Barbro Dahlén, MD, PhD; Craig E. Wheelock, PhD; Parameswaran Nair, MD, PhD; Sven-Erik Dahlén, MD, PhD; Paul M. O’Byrne, MB
Chest. 2014. doi:10.1378/chest.14-1214