Previous studies have suggested that there may be benefits to taking fish oil (omega-3) supplements, however, the benefits have not been clear. The ASCEND trial set out to rigorously test the benefits through a randomised controlled trial.
The study involved 15,480 people with diabetes (of any type of diabetes) and no prior history of cardiovascular disease. They were randomly assigned to either fish oil supplementation (1g daily) or a placebo (1g of olive oil). The participants were recruited between 2005 and 2011 and were monitored for an average of 7.4 years.
The health of the participants was monitored for about seven and a half years to check for serious heart and vascular disease events such as heart attack, stroke, transient ischemic attack (sometimes referred to as a mini stroke) and death from vascular problems.
The results showed that during the follow-up period, 8.9% of people in the fish oil group experienced a serious vascular event, compared to 9.2% in the placebo group. The results were deemed not to be statistically different and therefore it cannot be said that the fish oil supplements demonstrated a benefit over the olive oil placebo.
Professor Louise Bowman, principal investigator at Nuffield Department of Population Health, University of Oxford, said: “Our large, long-term randomised trial shows that fish oil supplements do not reduce the risk of cardiovascular events in patients with diabetes.
“This is a disappointing finding, but it is in line with previous randomised trials in other types of patient at increased risk of cardiovascular events which also showed no benefit of fish oil supplements. There is no justification for recommending fish oil supplements to protect against cardiovascular events.”
The results of the study have been published in the New England Journal of Medicine.