Do marine fatty acids improve asthma control? A systematic review of randomised controlled trials

The evidence for a dietary intake that is high in n-3 fatty acids is controversial. Whilst epidemiological studies have provided some support for this hypothesis, the data from intervention studies has been conflicting. Aim: To conduct a systematic review of all published randomised controlled trials (RCT) of n-3 fatty acid modification in adults and children (>2 years of age) to determine the overall effect of fish oil modification in asthma. This review was approved by the Cochrane Airways Group. Methods: A protocol was developed outlining the objectives, selection criteria, search strategy, retrieval and inclusion of studies, assessment of methodological quality, data extraction and statistical considerations. All published RCT's of n-3 fatty acid modification in adults and children (> 2 years of age) with asthma were identified and the methodological quality of these trials was assessed. Articles were identified using a defined search strategy. Manufacturers of n-3 fatty acid supplements and fish industry resources were also contacted for additional published and unpublished trials. Each article was assessed independently, by each of the three reviewers, to determine whether it met the criteria for inclusion in the review. The reviewers were blinded to the authors, journal,-language and results of each article. Results: Twenty articles, which related to 17 studies, were identified for possible inclusion. After reviewing the methods section of each of these 17 studies, 8 were excluded from the review as they did not meet the selection criteria and a further 3 studies require further clarification of their methods. Therefore 6 - 9 studies will be included in the meta-analysis. Conclusion: The studies which are to be included in the analysis do not suggest an improvement in asthma outcome following an increase in marine fatty acid consumption but the pooled analysis is yet to be completed.