Heart attack: omega-3 rich fish and seeds reduce risk of death by 10%

Following a diet rich in plant- and marine-derived omega-3s can reduce the risk of death from heart attack. High blood concentrations of alpha linoleic acid found in some seeds, such as flax or chia seeds, and EPA, DHA, and DPA, in which fish oil is rich, are associated with a 10 percent lower risk of fatal cardiac events.

This is the result of research published in JAMA Internal Medicine and conducted by researchers at several prestigious centers including Stanford University School of Medicine and Tufts University in Boston (USA)

Omega-3s of plant and marine origin

Alpha-linoleic acid (ALA) is an essential omega-3 fatty acid, that is, it must be consumed in the diet because the body is unable to produce it. ALA is the precursor from which the best-known omega-3 fatty acids originate: EPA and DHA found in high concentrations in the oil of fish that inhabit cold waters, such as salmon, cod, mackerel, tuna etc. The content of ALA in fish products is quite low (generally less than 1 percent), while it is found in fair amounts in some plant-based foods including chia seeds, flax seeds and flaxseed oil, cranberry seeds, walnuts, walnut oil, and soybean oil. While these foods are excellent sources of ALA, they are poor in its derivatives EPA and DHA. ALA possesses a number of beneficial functions for the body: it acts as an antiplatelet, vasoprotective and antithrombotic; in particular, it reduces the viscosity level of platelets by altering their aggregating potential and thus counteracting the formation of atherosclerotic plaques; it also protects blood vessels from injury. Through these actions it contributes to cardiovascular risk reduction, along with the omega-3 EPA and DHA, which are well known for their benefits on cardiac health such as reducing the risk of arrhythmias and mortality, in patients with recent myocardial infarction or heart failure. Despite the knowledge about the actions of plant-derived omega-3s, most studies on the cardioprotective activity of polyunsaturated fatty acids have been performed on EPA and DHA.

Plant-derived omega-3s also protect the heart

The one carried out by the U.S. researchers is a meta-analysis study, that is, it compared the results of dozens of other studies on plant- and marine-derived omega-3s and cardiac events. The results showed that subjects with the highest levels of omega-3 in their blood had a 25 percent lower risk of dying from a heart attack, compared with those with the lowest levels. Overall, omega-3 from plant sources and fish products were found to be associated with a 10 percent lower risk of fatal cardiac events, while no link was found between high levels of omega-3 from fish and nonfatal heart attacks. In detail, the results showed that ALA was associated with a 9% lower risk of fatal heart attack, while DPA and DHA with a 10% lower risk. DPA was also found to be related to a 6 percent lower risk of heart attack overall. This, according to Liana Del Gobbo, the research associate who led the study, suggests a mechanism by which omega-3s specifically counteract the risk of death. The new findings, along with those of other recent studies, provide a more complete and up-to-date picture of how omega-3s may affect heart disease. Two other authors of the research, Dariush Mozaffarian and Victoria Taylor, also emphasized that the study first confirms the importance of consuming fatty fish, as part of a healthy, balanced diet, in protecting heart health, and suggests a positive role of omega-3s that come from plant sources, such as flaxseed, canola and soybean oils. The study results came just days after another meta-analysispublished in the journal Clinical Nutrition showed that patients undergoing cardiac surgery who had consumed omega-3 supplements, prior to surgery, showed reduced postoperative arrhythmia and a 2.4-day shorter length of hospital stay, compared with those who had received placebo.

Some details of the meta-analysis

The study included data from as many as 45,637 participants from 16 different countries. For each, the researchers collected information on the concentrations of molecules in the blood derived from the omega-3s in fish: DHA, EPA, DPA (the docosapentaenoic acid) and those derived from ALA. In addition, the concentrations of other lipids in the blood including phospholipids and cholesterol esters, and the amount of adipose tissue were also measured for each subject, relating them to the presence of coronary artery disease. According to Dr. Mozaffarian, taking measures of omega-3 levels in the blood is important because most previous research has analyzed omega-3 estimates obtained by calculating them from the diet of test subjects, an inaccurate methodology with which one can easily fall into error.

A groundbreaking study in need of further study

According to the researchers who directed the meta-analysis, concentrations of molecules derived from marine- and plant-derived omega-3s are associated with a lower incidence of fatal coronary heart disease, and the new approach may offer an unprecedented opportunity to understand how molecules measured in the blood and derived from omega-3s of different origins may affect health. Although the new research provides further evidence on the benefits of omega-3s, more such analyses need to be pursued and, above all, work on consumer information and education. Indeed, it has recently been shown that most of the world's population consumes too little omega-3 to enjoy any cardiovascular benefits. Thus, few people follow the healthy eating recommendations that suggest eating at least one serving of oily fish per week. Statistics have shown that in some parts of the world only one third is consumed. In this regard, Harry Rice vice-president of the World Organization for EPA and DHA (GOED), commented on the publication, reminding that all omega-3s are necessary for health, but the results on cardiovascular risk reduction are greatest when EPA and DHA reach levels comparable to those observed in the Japanese population, and that in Western populations ALA consumption is almost always adequate while that of EPA and DHA is still far from the optimal dose.

Source: Del Gobbo LC, Imamura F, Aslibekyan S, et al. "'ω-3 Polyunsaturated Fatty Acid Biomarkers and Coronary Heart Disease: Pooling Project of 19 Cohort Studies" JAMA Internal Medicine.