Fish oil, rich in omega-3 polyunsaturated fatty acids (PUFAs) such as EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), has a scientific basis for use in the management of Congestive Heart Failure (CHF). Several randomized controlled trials and meta-analyses have evaluated its efficacy in this context. One of the most notable studies is the GISSI-HF trial (2008), which included over 6,000 patients with chronic heart failure. This trial demonstrated that supplementation with 1 gram daily of omega-3 PUFAs resulted in a modest but statistically significant reduction in both mortality and hospitalizations due to cardiovascular causes compared to placebo.

Mechanistically, omega-3 fatty acids are believed to exert their benefits by improving endothelial function, reducing inflammation, attenuating ventricular arrhythmias, and possibly improving left ventricular systolic function. The American Heart Association acknowledges the possible benefits of omega-3 supplementation as adjunctive therapy in heart failure, primarily based on existing clinical trial data.

However, the magnitude of benefit is considered modest, and guidelines do not recommend it as a stand-alone or first-line therapy but rather as an adjunct to standard pharmacological treatments. Some studies have shown less robust results, and the overall evidence quality is considered moderate, hence a rating of 3 out of 5.