Omega 3 for the heart: new evidence on their effectiveness

They reduce the risk of death from heart-related causes, but an in-depth analysis of decades of research also reveals other potentials. Here’s why Omega 3s are good for the heart

There seems to be very little room for doubt: Omega 3s are the ultimate fats allied with heart health. Even a thorough analysis of the latest review of studies on the topic leads to this conclusion: taking Omega 3 supplements actually reduces the risk of death from heart-related causes (coronary heart disease). 

The review in question, the result of work by the Cochrane Collaboration (an international non-profit network that provides authoritative, relevant, and reliable health information), was published in the Cochrane Library by a group of researchers led by experts from the Norwich Medical School (Norwich, UK) whose aim was to clarify the levels of Omega 3 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.” However, a more detailed analysis, such as that conducted during other reviews of the available scientific evidence, leads to a very different conclusion, revealing the significant effect associated with Omega 3 treatments.

• Omega 3 and heart health: the state of the art
• Benefits against coronary heart disease
• Masked advantages
• Omega 3 and deaths from heart-related causes

Omega 3 and heart health: the state of the art

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

However, randomized controlled trials testing the use of these Omega 3s for the prevention of disorders affecting the heart and arteries have produced conflicting results.

What is a randomized controlled trial?

The analysis published in the Cochrane Library took these studies into consideration. But what exactly is it? A randomized controlled trial is a study in which participants are randomly assigned to a group that will receive the treatment under investigation (in this case, Omega 3 supplementation) or a control group that will receive no treatment or a placebo. It is a quantitative study: the results of the intervention are measured. In this case, the measured outcomes were:

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

Benefits against coronary heart disease

The Cochrane review associated positive effects with Omega 3s. Some involve blood lipid levels. Omega 3s have indeed been confirmed to be effective in reducing triglycerides (an effect also recognized by EFSA, the European Food Safety Authority) and in increasing HDL (the so-called “good cholesterol”). 

Others concern the ability of Omega 3s to reduce events associated with coronary heart disease. The authors dismissed this evidence – which was statistically significant – as an error; however, a previous meta-analysis had already established that the detected effect is significant and real. The real mistake was not following Cochrane’s own guidelines on evaluating different sources of error, a major limitation of this analysis. 

Masked advantages

Unfortunately, the review published by the Cochrane Collaboration focused only on part of the scientific evidence available on the benefits of Omega 3s; in fact, decades of research have provided not only randomized controlled trials but also meta-analyses (i.e., statistical analyses that consider results from multiple studies and produce a weighted average), epidemiological studies, as well as in vitro and animal model research. Furthermore, the authors excluded at least one study a priori without adhering to predefined exclusion criteria, and the analysis contradicts previous meta-analyses that more closely examined some of the most relevant effects achievable with Omega 3 administration – particularly those on deaths from heart-related causes, blood pressure, and triglycerides. Focusing on these aspects, the review would have been characterized by the same depth of analysis as previous publications and could have detected other positive effects related to Omega 3 intake. 

Additionally, the definition chosen by the authors for “cardiovascular mortality” differs from the one commonly used and, compared to other previously published meta-analyses, limits the number of events considered; this choice further reduces the likelihood of detecting significant effects, especially given that the new review does not include a sufficient number of participants. In fact, about 73,000 cases were considered (less than 37,000 for each group – treatment and control) while to evaluate the possibility that Omega 3s have an effect avoiding false negatives (i.e., the risk of not seeing an effect when there actually is one) about 155,000 cases per group would have been necessary. 

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

Omega 3 and deaths from heart-related causes

In the past, other researchers have analyzed in more detail the effects of Omega 3 administration, confirming the reduction in the risk of dying from heart-related causes. Their conclusions support the recommendations of the American Heart Association according to which Omega 3 treatments are “reasonable”:

• for the secondary prevention of death from heart-related causes and sudden cardiac death in patients with coronary heart disease;
• for the secondary prevention of adverse events in patients with heart failure.

Considering the low risk of side effects associated with Omega 3 supplementation, any benefit, even modest, should be considered significant. However, the same meta-analyses that confirmed the benefits of Omega 3s against deaths from heart-related causes identified other factors to consider:

• Omega 3 dosage – treatments that proved most effective used doses of EPA+DHA greater than 1 gram per day;
• baseline cardiovascular risk – treatments were more effective in patients with high triglycerides or “bad” cholesterol (equal to or greater than 150 mg/dl or 130 mg/dl, respectively);
• statin use – treatment efficacy was greater in studies with less frequent statin use.

Taking all these factors into account, it is possible to decide whether to opt for Omega 3 supplementation and evaluate the potential benefits.  

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