Fish oils are so effective at helping protect against heart attacks, they should be taken daily by everyone, say doctors in a new review of the effects of omega-3 fatty acids.

The doctors say their review found that there is now "compelling" evidence that the omega-3 fatty acids in certain fish and other sources not only prevent cardiovascular disease, but may even help treat it.

The study, published in the Journal of the American College of Cardiology, reviewed data on four trials involving almost 40,000 participants that showed the benefits of omega-3 fatty acids in the prevention of cardiovascular disease, in treatment after heart attack and, most recently, in heart failure patients.

Lead author Dr. Carl Lavie, medical director of Cardiac Rehabilitation and Prevention at the Ochsner Medical Center in New Orleans, said people have been hearing for years that fish and omega-3 fatty acids are a good thing, but many don't realize how effective they are for heart health.

"This isn't just hype; we now have tremendous and compelling evidence from very large studies, some dating back 20 and 30 years, that demonstrate the protective benefits of omega-3 fish oil in multiple aspects of preventive cardiology," Lavie said in a statement.

"The strongest evidence of a cardio-protective effect of omega-3s appears in patients with established cardiovascular disease and following a heart attack, with up to a 30 per cent reduction in CV-related death."

Not only can they help heart patients who have already had heart attacks, fish oil can also decrease the risk of atherosclerosis, arrhythmia and sudden cardiac death.

Dr. Lavie adds although there is a smaller benefit in reducing death from heart failure death--9 per cent mortality benefit in a major recent randomized controlled trial--this is still impressive, given patients' grave prognosis.

"If we translate this finding, it means that we only need to treat 56 patients for four years to prevent one death," he said.

"And we are talking about a very safe and relatively inexpensive therapy."

According to Dr. Lavie, the fatty acids EPA and DHA work by getting into the membranes of cells and help to improve the heart's electrical activity, as well as its vascular tone, plaque stabilization and blood pressure.

Based on these findings, and because the body does not produce its own essential fatty acids, the authors recommend that healthy individuals consume 500 mg of omega-3 fish oil containing EPA and DHA a day.

People with known heart disease or heart failure should aim for even more -- at least 800 to 1,000 mg daily.

They also advise increasing one's intake of oily fish such as salmon, sardines, trout, herring, and oysters.

"Patients should talk with their doctors about whether a fish oil supplement is needed to get the right amount and, in turn, benefit from the associated cardiovascular protection."

Authors say further studies are needed to investigate and determine optimal dosages, as well as the relative ratio of DHA to EPA that provides maximal heart protection.