Fish oils are also extremely beneficial to the cardiovascular system. Unlike other fats, fish oils can protect against heart disease rather than contribute to its development. Omega-3 fatty acids appear to have the ability to lower cholesterol levels and blood pressure, prevent blood clots and maintain the elasticity of blood vessels.

Two very large studies have shown that fish oil very powerfully reduces the risk of cardiovascular disease. Among patients who have experienced a heart attack, fish oil supplementation demon- strated a 45% reduction in risk of sudden coronary death and a 25% reduction in death from any cardiac cause!

A second study among otherwise healthy people demonstrated a 20%-30% reduction in risk of major coronary events. This compelling evidence has lead both the American Heart Association and the American Diabetes Association to openly recommend the daily consumption of fish and/or daily use of fish oil supplements.

Fish oil has also been shown to reduce the pain of inflammation. It is particularly effective in helping to ease the pain of arthritis and colitis, and fish oil supplements may reduce the need for NSAIDs and other pain medications in patients who suffer from inflammatory conditions.

Ref link: 

https://www.health.harvard.edu/staying-healthy/do-fish-oil-supplements-reduce-inflammation