Omega 3 for the heart: new evidence on their effectiveness

They reduce the risk of death from heart causes, but an in-depth analysis of decades of research reveals other potentials as well. Here's why omega-3s are good for the heart

By now there seems to be little room for doubt: Omega 3 is the ultimate heart-allied fat. An in-depth analysis of the latest review of studies conducted on the subject also leads to this conclusion: taking Omega 3 supplements does indeed reduce the risk of death from cardiac causes (coronary heart disease). 

The review in question, the result of the work of the Cochrane Collaboration (an international nonprofit network dedicated to providing authoritative, relevant and reliable information regarding health), was published in the Cochrane Library by a group of researchers led by experts from Norwich Medical School (Norwich, UK) whose intent was to clarify what levels of Omega 3 are associated with reducing the risk of cardiovascular problems by analyzing randomized controlled trials conducted to date. 

According to its authors, "increasing EPA and DHA [respectively, eicosapentaenoic acid and docosahexaenoic acid, the two Omega 3s abundant in fatty fish and fish oil, ed.] has little or no effect on mortality or cardiovascular health." A more detailed analysis, such as that conducted during other reviews of the available scientific evidence, however, leads to a quite different conclusion, noting the significant effect associated with Omega 3 treatments.

• Omega 3 and heart health: the state of the art
• Benefits against coronary heart disease
• Masked benefits
• Omega 3s and deaths from cardiac causes

Omega 3 and heart health: the state of the art

Omega-3s are essential fatty acids. In fact, the human body cannot synthesize their progenitor (alpha-linolenic acid, ALA) and cannot efficiently convert it into the two molecules it actually needs, EPA and DHA. Years of research have demonstrated the association between a diet rich in these Omega 3s and good heart and artery health. First to unveil this phenomenon was the study of Inuit Eskimo populations: diets rich in sources of EPA and DHA (particularly Omega 3-rich fish) are associated with a limited incidence of cardiovascular problems. 

However, randomized controlled trials that have tested the use of these Omega 3s for the prevention of disorders that can affect the heart and arteries have produced mixed results.

What is a randomized controlled trial?

The analysis published in the Cochrane Library looked at these very studies. But what exactly are they? A randomized controlled trial is a study in which participants are randomly assigned to either a group that will be given the treatment being analyzed (in this case, the administration of Omega 3) or a control group that will receive no treatment or a placebo. This is a quantitative study: the results of the intervention are measured. In this case, the outcomes measured were:

• mortality from all causes;
• mortality from cardiovascular causes;
• cardiovascular events;
• coronary heart disease mortality;
• events associated with coronary heart disease;
• strokes;
• arrhythmias;
• adiposity;
• lipid levels.

Benefits against coronary heart disease

The Cochrane review associated Omega 3 with positive effects. Some relate to blood lipid levels. In fact, Omega 3s were reconfirmed to be effective in reducing triglycerides (an effect not surprisingly also recognized by Efsa, the European Food Safety Authority) and capable of raising HDL (the so-called "good cholesterol"). 

Others concern the ability of Omega 3 to reduce events associated with coronary heart disease. The authors dismissed this evidence-although statistically significant-attributing it to error; however, a previous meta-analysis had already established that what was detected was a significant and real effect. The real error was in not following Cochrane's own guidelines on the evaluation of different sources of error, a strong limitation of this analysis. 

Masked benefits

Unfortunately, the review published by the Cochrane Collaboration focused only on part of the available scientific evidence on the benefits of Omega 3; in fact, decades of research have left us not only with randomized controlled trials, but also with meta-analyses (i.e., statistical analyses that take into account the results of different studies by making a sort of weighted average) and epidemiological studies, as well as research conducted in vitro and in animal models. In addition, its authors excluded at least one study a priori without adhering to predefined exclusion criteria, and the analysis conducted contradicts previous meta-analyses that have focused more closely on some of the more relevant effects achievable through Omega 3 supplementation-particularly those on cardiac deaths, blood pressure, and triglycerides. By focusing on these aspects, the review would have been characterized by the same depth of analysis as the publications that preceded it and could have detected other positive effects associated with Omega 3 intake as well.  

Added to this is the fact that the definition chosen by the authors for what is called "mortality from cardiovascular causes" is different from the one usually used, and compared with other already published meta-analyses it limits the number of events taken into account; this choice also reduces the likelihood of detecting significant effects, even more so in light of the fact that the new review does not include a sufficient number of participants. In fact, there were about 73,000 cases considered (less than 37,000 for each group-treatment and control), whereas to assess the possibility that omega-3 has an effect while avoiding the risk of false-negative results (i.e., the risk of seeing no effect when in fact there is an effect) would have required analyzing about 155,000 cases for each group. 

In conclusion, the benefits that could have emerged from such a review go beyond those highlighted by the authors of the Cochrane publication.

Omega 3 and deaths from cardiac causes.

Other researchers have previously analyzed the effects of Omega 3 supplementation in more detail, confirming the reduction in the risk of dying from heart-related causes. Their findings support the American Heart Association's recommendations that Omega 3 treatments "are reasonable."

• for the secondary prevention of cardiac deaths and sudden cardiac death among patients with coronary heart disease;
• For secondary prevention of adverse events in patients with heart failure.

If one then takes into account the low risk of side effects associated with Omega 3 supplementation, any benefit, however modest, should be considered significant. Beware, however: the same meta-analyses that have confirmed the benefits of Omega 3 against cardiac deaths have identified other factors to consider:

• Omega 3 dosage-the treatments that have been shown to be most effective are those in which doses of EPA+DHA greater than 1 gram per day have been used;
• baseline cardiovascular risk-the treatments were most effective among patients with high triglycerides or "bad" cholesterol (equal to or greater than, respectively, 150 mg/dl or 130 mg/dl);
• statin intake--treatment efficacy was higher in studies in which less statin use was made.

By taking all these factors into consideration, it is possible to choose whether to opt for Omega 3 intake and to evaluate what benefits you can gain from it.   

Sources: Abdelhamid AS et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2018 Jul 18;7:CD003177. doi: 10.1002/14651858.CD003177.pub3 Alexander et al. A Meta-Analysis of Randomized Controlled Trials and Prospective Cohort Studies of Eicosapentaenoic and Docosahexaenoic Long-Chain Omega-3 Fatty Acids and Coronary Heart Disease Risk. Mayo Clin Proc. 2017 Jan;92(1):15-29. doi: 10.1016/j.mayocp.2016.10.018 Dyerberg J and Bang HO. Haemostatic function and platelet polyunsaturated fatty acids in Eskimos. Lancet. 1979 Sep 1;2(8140):433-5 European Commission. EU Register of nutrition and health claims made on foods. https://goo.gl/faHW7R. 25/09/18 Maki KC and Dicklin MR. Omega-3 Fatty Acid Supplementation and Cardiovascular Disease Risk: Glass Half Full or Time to Nail the Coffin Shut? Nutrients. 2018 Jul 4;10(7). doi: 10.3390/nu10070864 Maki KC et al. Use of supplemental long-chain omega-3 fatty acids and risk for cardiac death: An updated meta-analysis and review of research gaps. J Clin Lipidol. 2017 Sep - Oct;11(5):1152-1160.e2. doi: 10.1016/j.jacl.2017.07.010 The Goed Current - Breaking News. Negative Cochrane Review on Omega-3s and Cardiovascular Outcomes Published. 2018 July 17 Image:Pixabay