The American Heart Association recommends that adults consume at least eight ounces of fish and shellfish each week, especially those that are rich in omega-3 fatty acids. Previous research supports the benefits of omega-3 consumption in preventing coronary heart disease and sudden cardiac death; however, additional research is needed to support the benefits of omega-3s for other cardiovascular disorders. Investigators reviewed the molecular, clinical, and epidemiological evidence for the effects of omega-3s on cardiovascular disease.
Omega-3 fatty acids cannot be produced by the body and must be consumed in the diet. Major food sources of omega-3s include fatty fish, which are rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Plant sources of omega-3s include flax seeds, chia seeds, and walnuts, but the predominant omega-3 fat in these foods is alpha-linolenic acid, which must be converted to EPA before it can be used by the body. Omega-3s and their metabolites improve cardiovascular health through altering the composition of cell membranes and regulating gene expression, among other functions.
The authors searched the literature for randomized controlled trials, in which researchers randomly assign participants to an intervention or a comparable control treatment, and observational studies, which observe a group of participants at a single time point. Randomized controlled trials are suitable for identifying cause-and-effect relationships, but because observational studies measure associations between behavior and health, they are not. Review papers aggregate data from previous research and compare results, a process that can be difficult because dose, sample size, and participant characteristics vary among studies.
The analysis revealed that the dose of omega-3s utilized in the randomized controlled trials ranged from 376 milligrams to 1,800 milligrams. Some of these trials instructed participants to consume the recommended two servings of fish per week. Data from these trials showed that omega-3 consumption decreased cardiovascular disease, with risk reductions ranging from two to 32 percent among trials; however, some trials did not find a benefit of omega-3 consumption for reducing the risk of death from cardiovascular disease. In observational studies, the benefits of omega-3 consumption were strongest for coronary heart disease and sudden cardiac death, confirming previous reports. Evidence from the randomized controlled trials and observational studies was inadequate to support assertions that consumption of omega-3 fatty acids reduce the risk of heart attack, stroke, atrial fibrillation, arrhythmias, and heart failure.
Current data support the consumption of omega-3s for reduced risk of death from cardiovascular disease. The authors concluded that future research should explore the effects of dose, source (i.e., seafood or supplements; plant or animal), and other molecular, physiological, and clinical effects.