Fish, including both finfish and shellfish, is scientifically validated as beneficial for heart health. This is primarily due to the high content of omega-3 polyunsaturated fatty acids (EPA and DHA) found in many types of fish, especially fatty fish such as salmon, mackerel, sardines, and anchovies. Numerous epidemiological studies and randomized controlled trials have consistently shown that regular consumption of fish is associated with a reduced risk of cardiovascular disease (CVD), including coronary heart disease and stroke.

In 2002, the American Heart Association recommended consuming fish (particularly fatty fish) at least twice a week to support cardiovascular health. Meta-analyses demonstrate that fish intake lowers triglycerides, reduces blood pressure, decreases arrhythmias, and modestly raises HDL cholesterol. The omega-3 fatty acids in fish are thought to exert anti-inflammatory, anti-thrombotic, and anti-arrhythmic effects. For shellfish, while they are generally lower in omega-3s than finfish, they can still contribute to heart health and are low in saturated fat.

The strongest evidence supports the preventive rather than curative role of fish for maintaining heart health and lowering risk factors associated with heart disease. However, people with existing heart disease are also often advised by clinicians to increase omega-3 intake, often through fish or fish oil, to support cardiac function.