Three recent large and well-controlled studies showed that omega-3 fish oil pills did not prevent heart attacks or surgical procedures for heart disease in people at high risk for heart attacks, while one study showed reduced heart disease:
• The STRENGTH TRIAL found no significant difference between 6539 patients receiving high doses (4g/day) of omega-3 pills and 6539 patients receiving an equivalent amount of corn oil for 42 months, in the number of deaths from heart disease, nonfatal heart attacks, nonfatal strokes, heart bypass procedures or hospitalization for chest pain (JAMA, Nov 15, 2020).
• The VITAL trial found no benefit in 25,871 participants who received omega-3 (1 g/day), vitamin D or placebo pills (N Engl J Med, 2019;380(1):23-32).
• The OMEMI Trial (OMega-3 fatty acids in Elderly patients with Myocardial Infarction) from Oslo, Norway found that omega-3 pills given for two years failed to prevent heart complications in elderly patients with recent heart attacks, and were associated with increased risk for atrial fibrillation and bleeding events (Circulation, published online November 15, 2020).
• The REDUCE-IT trial (Reduction of Cardiovascular Events with Icosapent Ethyl–Intervention Trial) found that 8179 people who took 4 g/day of omega-3 fatty acids for 4.9 years had reduced risk for heart diseases, compared to the placebo group that was given mineral oil pills (N Engl J Med, 2019;380(1):11-22).
An earlier review of 79 controlled studies of more than 110,000 men and women, with or without heart disease, showed that fish oil pills taken for one to six years did not prevent heart attacks, strokes or deaths in general (Cochrane Review, July 18, 2018). See Fish Oil and Cod Liver Oil Pills Not Shown to Prevent Heart Attacks
A Possible Explanation of the Differing Results
An editorial in the Journal of the American Medical Association summed up the current evidence (JAMA, published online November 15, 2020). It is possible that in the REDUCE-IT trial, the omega-3s did not reduce heart disease, but the mineral oil given as a placebo increased heart attack risk. The mineral oil group suffered an increase in blood levels of the harmful LDL cholesterol, apoB and high-sensitivity CRP that are associated with increased the risk of cardiovascular events. However, the U.S. Food and Drug Administration (FDA) concluded that only a small fraction of the difference in outcomes between omega-3 and mineral oil pills could be explained by a harmful effect of mineral oil (FDA Briefing on REDUCE-IT, November 14, 2019; 76-77, 112-114).
The JAMA editorial’s authors believe that “Continued scientific discovery and rigorous research will be necessary to get closer to the truth.” Even though doctors have no strong evidence that fish oil pills help to prevent heart attacks, people world-wide now spend more than $4.1 billion each year on fish oil pills. Further studies on these supplements are unlikely to be done since large studies are very expensive and omega-3 pills cannot be patented, so there is no profit motive.
The evidence that eating fish twice a week helps to prevent heart attacks is so strong that I believe everyone should do that. If you don’t like fish and want to take omega-3 pills instead, realize that the evidence really does not support taking them. Some brands may contain toxic amounts of heavy metals found in aging fish, so you may be taking a risk for mercury poisoning unless you can check the source of your omega-3 pills. Also, remember to test for rancidity by breaking open a capsule from each bottle of fish oil pills you purchase. If they smell fishy, throw the whole bottle out, since rancid oxidized fish oils can increase risk for heart attacks and certain cancers. If you are a vegan who eats no foods from animals, you should take vitamin B12 pills to prevent nerve damage and dementia caused by lack of that vitamin.