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Full Title: Health Effects of Omega-3 Fatty Acids on Asthma
View or download Summary/Report
Objectives: To systematically review the scientific-medical literature regarding evidence for the health effects of omega-3 fatty acids in asthma, specifically to address:
- Efficacy in improving respiratory outcomes.
- Impact of omega-3 fatty acid source, type, and dose on efficacy.
- Influence on suspected proinflammatory mediators of asthma.
- Value of omega-3 fatty acids in primary or secondary prevention.
- The safety profile of omega-3 fatty acids in asthma populations, subpopulations, or those at risk.
Data Sources: MEDLINE®, PreMEDLINE®, EMBASE,
Cochrane Central Register of Controlled Trials, CAB Health, and, Dissertation
Abstracts were searched without restriction by language of publication, publication
type, or (in most cases) by study design. Additional references were sought
through manual searches of included studies' reference lists and key review articles, and from content experts.
Review Methods: Studies were considered relevant if they described human populations of any age, involved any type of study design, and investigated the use of any foods or extracts known to contain omega-3 fatty acids as a treatment, or primary or secondary prevention for asthma. Data was extracted regarding study design, population, intervention/exposure and comparator(s), co-interventions, withdrawals and dropouts, and outcomes (including safety). Study quality and applicability were rated as well.
Results: The researchers performed qualitative syntheses of the evidence for each question from 31 reports describing 26 unique studies. Problems and limitations of available studies made it inappropriate to conduct meta-analysis of randomized, controlled trial (RCT) evidence for any of the five questions because of missing data, flawed designs, and noncomparable study parameters. Greater emphasis was placed on RCT evidence, given its status as the gold standard for measuring efficacy or effectiveness. Forced expiratory volume in one second (FEV1), a gold standard index of pulmonary function, was selected as the primary outcome.
Conclusions: Aside from an acceptable safety profile, it is impossible to definitively conclude anything with respect to the value of using omega-3 fatty acid supplementation in asthma for adults or children, either in or beyond North America. The lack of sufficiently consistent evidence—as well as a paucity of evidence from well-designed, well-conducted and adequately powered studies—suggests that no definitive conclusion can yet be drawn regarding the efficacy of omega-3 fatty acid supplementation as an asthma treatment. Future research investigating North American samples is likely to be needed to establish or refute the value of omega-3 fatty acids in the treatment or prevention of asthma in North American adults and children.
Health Effects of Omega-3 Fatty Acids on Asthma
Evidence-based Practice Center: University of Ottawa
Topic Nominator: Office of Dietary Supplements, National Institutes of Health
Current as of March 2004