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Effect of fish oil on arrhythmias and mortality: systematic review

BMJ 2008; 337 doi: (Published 24 December 2008) Cite this as: BMJ 2008;337:a2931
  1. Hernando León, postgraduate in internal medicine and former postdoctoral clinical research fellow 12,
  2. Marcelo C Shibata, associate clinical professor12,
  3. Soori Sivakumaran, associate clinical professor of medicine12,
  4. Marlene Dorgan, head 3,
  5. Trish Chatterley, research librarian3,
  6. Ross T Tsuyuki, professor of medicine (cardiology) and director12
  1. 1Epidemiology Coordinating and Research (EPICORE) Centre, Edmonton, AB, Canada
  2. 2Department of Medicine, Division of Cardiology, Faculty of Medicine and Dentistry, University of Alberta, 220 College Plaza, Edmonton, AB, Canada T6G 2C8
  3. 3Institute of Health Economics and John W Scott Health Sciences Library, University of Alberta
  1. Correspondence to: R T Tsuyuki ross.tsuyuki{at}
  • Accepted 1 October 2008


Objective To synthesise the literature on the effects of fish oil—docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)—on mortality and arrhythmias and to explore dose response and formulation effects.

Design Systematic review and meta-analysis.

Data sources Medline, Embase, the Cochrane Library, PubMed, CINAHL, IPA, Web of Science, Scopus, Pascal, Allied and Complementary Medicine, Academic OneFile, ProQuest Dissertations and Theses, Evidence-Based Complementary Medicine, and LILACS.

Studies reviewed Randomised controlled trials of fish oil as dietary supplements in humans.

Data extraction The primary outcomes of interest were the arrhythmic end points of appropriate implantable cardiac defibrillator intervention and sudden cardiac death. The secondary outcomes were all cause mortality and death from cardiac causes. Subgroup analyses included the effect of formulations of EPA and DHA on death from cardiac causes and effects of fish oil in patients with coronary artery disease or myocardial infarction.

Data synthesis 12 studies totalling 32 779 patients met the inclusion criteria. A neutral effect was reported in three studies (n=1148) for appropriate implantable cardiac defibrillator intervention (odds ratio 0.90, 95% confidence interval 0.55 to 1.46) and in six studies (n=31 111) for sudden cardiac death (0.81, 0.52 to 1.25). 11 studies (n=32 439 and n=32 519) provided data on the effects of fish oil on all cause mortality (0.92, 0.82 to 1.03) and a reduction in deaths from cardiac causes (0.80, 0.69 to 0.92). The dose-response relation for DHA and EPA on reduction in deaths from cardiac causes was not significant.

Conclusions Fish oil supplementation was associated with a significant reduction in deaths from cardiac causes but had no effect on arrhythmias or all cause mortality. Evidence to recommend an optimal formulation of EPA or DHA to reduce these outcomes is insufficient. Fish oils are a heterogeneous product, and the optimal formulations for DHA and EPA remain unclear.


  • We thank Scot Simpson for his help with Rev Man Software, Jeppe Hagstrup Christensen (Aalborg Hospital, Aarhus University Hospital, Denmark) for sharing his results, and Ben Vandermeer for his help with the meta-regression analysis. No compensation of any kind was received by them for their help in preparing this manuscript. HL is a recipient of a research fellowship from the Alberta Heritage Foundation for Medical Research. RTT is supported by the University of Alberta Merck Frosst chair in patient health management.

  • Contributors: HL conceived and designed the study, collected and analysed or interpreted the data, and prepared the manuscript. MCS helped design the study, collect data, and revise the manuscript. SS helped collect and analyse the data and revise the manuscript. MD and TC helped design the study, especially the literature search, and revise the manuscript. RTT helped conceive and design the study, analyse the data, and revise the manuscript. RT and HL are guarantors of this paper.

  • Funding: None.

  • Competing interests: None declared.

  • Ethical approval: Not required.

  • Provenance and peer review: Not commissioned; externally peer reviewed.

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