Fish oil (also called N-3 or omega-3 fatty acids) have been recommended in the past to decrease the chance of heart attacks and strokes. Harvard Medical Center sponsored a huge study involving more than 25,000 adults. The study included men and women, and all racial groups. These were individuals who did not have risk factors for cardiovascular disease, such as Diabetes, Hypertension, or elevated cholesterol. After more than 5 years, there was no difference between the fish oil and the placebo groups with regard to heart attacks, strokes, cancer, or all cause mortality. This was a high quality study with a low risk of bias, so its conclusion, that fish oil supplement is not worthwhile, is valid. New England Journal of Medicine, Jan 2019.