Consuming oily fish at least two to four times a week is recommended for patients after a heart attack. But the evidence for the protective effect of fish oil supplements is based on one large trial from over 10 years ago.
In an attempt to resolve the uncertainty, researchers systematically reviewed randomised trials of fish oil as a dietary supplement in the prevention of cardiac deaths and arrhythmias in more than 30,000 participants in 12 studies.
Fish oil was found to be effective at reducing deaths from heart problems, but showed no strong evidence of a beneficial effect on arrhythmias or deaths from all causes.
Three of the studies analysed the effect of fish oil supplementation on the reduction in implantable cardiac defibrillator interventions and reported a neutral effect. Six studies examined the effect of fish oil on sudden cardiac death and showed no benefit. A further 11 studies showed a 20% reduction in deaths from heart problems.
No evidence was found for a dose-response effect between type of fish oil and reduction in deaths from heart problems, so it was not possible for the researchers to suggest an optimal dose or formulation of fish oil.
The study was published online in the BMJ.