Fish oil may be helpful in preventing deaths related to heart problems, but there is a lack of evidence that it provides a clear benefit in heart rhythm problems, according to a study.
The authors of the study stressed the need for more funding for further studies on this neglected area of nutrient research.
While heart attack survivors are recommended the consumption of oily fish at least two to four times a week, the authors of the current study insist that the evidence for the protective effect of fish oil supplements is based on one large trial from over 10 years ago.
Posting their research paper on bmj.com, they underscored the fact that more recent trials had shown no beneficial effect of fish oil on patient outcomes.
Professor Ross Tsuyuki and colleagues from Canada set out to resolve the uncertainty by systematically reviewing randomised trials of fish oil as a dietary supplement in the prevention of cardiac deaths and heart rhythm problems, scientifically known as arrhythmias, in more than 30,000 participants in 12 studies.
The researcher observed that fish oil was effective at reducing deaths from heart problems, but it did not show any strong evidence of a beneficial effect on arrhythmias or deaths from all causes.
The team revealed that three of the studies involving over 11,000 participants analysed the effect of fish oil supplementation on the reduction in implantable cardiac defibrillator interventions, and showed a neutral effect.
They added that six studies of over 31, 000 patients examined the effect of fish oil on sudden cardiac death, and showed no benefit.
According to them, a further 11 studies showed a 20 per cent reduction in deaths from heart problems.
The researchers said that there was no evidence for a dose-response effect between type of fish oil and reduction in deaths from heart problems, and thus it was not possible for them to suggest an optimal dose or formulation of fish oil.
An accompanying editorial in the online edition of the journal, written by Dr Eric Brunner and Professor Hiroyasu Iso, said that the review highlighted the lack of high quality evidence and the neglect of this important area of nutrient research.
They insisted that there was a need for increased funding to resolve the uncertainty surrounding the protective effect of fish oil, to help the millions of people with heart disease.
They said that further studies were also important because they could help protect the world's marine life, which is facing extinction for commercial gain in the name of public health.