Omega 3 and 6 oils for primary prevention of allergic disease: Systematic review and meta-analysis

Background: There is conflicting evidence on the use of omega 3 and omega 6 supplementation for the prevention of allergic diseases. We conducted a systematic review evaluating the effectiveness of omega 3 and 6 oils for the primary prevention of sensitization and development of allergic disorders. Methods: We searched The Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, LILACS, PsycInfo, AMED, ISI Web of Science and Google Scholar for double-blind randomized controlled trials. Two authors independently assessed articles for inclusion. Meta-analyses were undertaken using fixed effects modelling, or random effects modelling in the event of detecting significant heterogeneity. Results: Of the 3129 articles identified, 10 reports (representing six unique studies) satisfied the inclusion criteria. Four studies compared omega 3 supplements with placebo and two studies compared omega 6 supplements with placebo. There was no clear evidence of benefit in relation to reduced risk of allergic sensitization or a favourable immunological profile. Meta-analyses failed to identify any consistent or clear benefits associated with use of omega 3 [atopic eczema: RR = 1.10 (95% CI 0.78-1.54); asthma: RR = 0.81 (95% CI 0.53-1.25); allergic rhinitis: RR = 0.80 (95% CI 0.34-1.89) or food allergy RR = 0.51 (95% CI 0.10-2.55)] or omega 6 oils [atopic eczema: RR = 0.80 (95% CI 0.56-1.16)] for the prevention of clinical disease. Conclusions: Contrary to the evidence from basic science and epidemiological studies, our systematic review and meta-analysis suggests that supplementation with omega 3 and omega 6 oils is probably unlikely to play an important role as a strategy for the primary prevention of sensitization or allergic disease. © 2009 John Wiley & Sons A/S.