A large-scale systematic meta-analysis collecting data from 79 trials has concluded that omega-3 supplements have little to no effect in preventing heart disease, stroke or death. The results stand in contrast to the commonly held belief that omega-3 supplements confer a variety of beneficial cardiovascular protections.

The meta-analysis concentrated on prior randomized trials that examined the impact of long-chain omega 3 supplements taken in capsule form. Seventy-nine trials were ultimately included in the analysis, comprising 112,059 subjects, with only a minority of the included studies assessing omega-3 consumed through whole fish diets.

"The review provides good evidence that taking long-chain omega 3 (fish oil, EPA or DHA) supplements does not benefit heart health or reduce our risk of stroke or death from any cause," explains Lee Hooper, lead author on the study. "The most trustworthy studies consistently showed little or no effect of long-chain omega 3 fats on cardiovascular health."

The results also showed that omega-3 supplementation made no difference to overall mortality rates with all-cause death rates sitting at nine percent in the control group and 8.8 percent in the omega-3 supplementation group.

Perhaps the most interesting issue raised by this study is the fact that it seems to contradict strong evidence from prior epidemiological research that has confidently correlated diets high in fish with lower rates of cardiovascular disease. Ian Johnson, a nutrition researcher from the Quadram Institute Bioscience, did not work on this new study but suggests maybe the benefits of oily fish in a diet are due to more than simply the presence of omega-3.

"Either the protective effects of oily fish consumption that are observed in populations are due to mechanisms that cannot be reproduced by relatively short-term interventions with purified omega 3 supplements, or perhaps they are caused by other unidentified environmental factors somehow linked to oily fish consumption," says Johnson.

In 2017 the American Heart Association affirmed its long-standing advice that omega-3 supplementation is beneficial to patients with prevalent coronary heart disease, or at high risk of cardiovascular disease. But, there has been growing debate over the last few years questioning whether there is evidence that clearly backs up that recommendation.

In 2016 the European Society of Cardiology suggested there isn't enough evidence to clearly justify the efficacy of omega-3 supplements. Another large-scale meta-analysis examining the associations between omega-3 and cardiovascular disease risk in 2017 also found no evidence that supplementation confers any protective benefits against coronary heart disease

Tim Chico, a cardiologist from the University of Sheffield, suggests the results from this latest meta-analysis confirm how complex it is to reduce a holistically healthy diet down to a single element.

"Previous experience has shown that although some types of diet are linked to lower risk of heart disease, when we try to identify the beneficial element of the diet and give it as a supplement it generally has little or no benefit," explains Chico. "This was the case for vitamins; we know a diet rich in vitamins is associated with lower risk of heart disease, but studies giving people vitamin pills showed that these gave no benefit and indeed may have caused harm."

The ultimate advice from many experts is that supplements are simply not a replacement for a healthy diet, and simply adding one vitamin or mineral in supplement form often confers very little positive benefit.

The new systematic review was published in Cochrane Library.