On radio and TV, ads fill the airwaves with claims about fish oil (with its omega-3 fatty acids) and its ability to prevent heart attacks.

The American Heart Association recommends fish oil for people with high levels of triglycerides in their blood, while doctors have recommended these capsules for people with heart problems.

According to Salon.com, these claims have come under scrutiny in a recent study by the Mario Negri Institute for Pharmacological Research in Milan.

This new study, which was published in the New England Journal of Medicine, says that people, who have a high risk of heart problems and are taking medications, will see little benefit from fish oil.

The researchers gave one gram of fish oil (per day) to one group of people and fake capsules to another test group. The study found that after five years, about 12 percent of each group suffered hospitalization for heart-related illnesses, heart attacks and strokes.

A similar study released in 2012 also questioned the benefits of fish oil, reported CNN.

That study covered 14 clinical trials that included more than 20,000 people with a history of heart disease. Researchers found no differences between people taking fish oil supplements or a placebo.

"There is no evidence that omega-3 supplementation is effective for secondary prevention of cardiovascular disease," stated lead study author Seung-Kwon Myung, M.D., a researcher of family medicine at Seoul National University, in South Korea.

Sources: CNN and Salon.com