Available evidence on omega-3 fatty acids and cardiovascular diseases
The results from prospective cohort studies showed that fish consumption is inversely related to cardiovascular diseases. The most likely explanation for this association are the effects of the fish fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Meta-analyses of randomized controlled trials showed that EPA-DHA supplementation did reduce markers of ventricular fibrillation, inflammation and endothelial dysfunction and platelet aggregation. Meta-analysis of the randomized controlled trials on EPA-DHA supplementation published before 2010 showed significant reductions of 20% for fatal coronary heart disease and approximately 15 % for sudden cardiac death. However, the trials published since 2010 did not confirm the effects on fatal coronary heart disease and sudden cardiac death.
One of the explanations for the different results obtained in the EPA-DHA supplementation trials before 2010 and from 2010 onwards could be the difference in drug treatment. In the recent trials the patients were state-of-the-art treated for thrombosis, elevated blood pressure and elevated LDL-cholesterol levels. That was not the case in the older trials. A substudy in the Alpha Omega Trial carried out in patients who did not use cholesterol-lowering statins showed that omega-3 fatty acids reduced major cardiovascular events by 54%. Another substudy in the Alpha Omega Trial showed that in patients after heart attack who also had diabetes reduced severe arrhythmia-related events by 84% and these events in combination with fatal heart attack by 72%.
The currently available evidence shows that omega-3 fatty acids do not affect major cardiovascular events in patients after heart attack who receive state-of-the-art drug treatment. However, in patients who do not use statins or have a high absolute risk because of e.g. the combination of having had a heart attack and also have diabetes, a protective effect of omega-3 fatty acids supplementation was observed. Therefore future trials on omega-3 fatty acids and cardiovascular endpoints will provide only useful information if they will be carried in patients with a high absolute risk.