Taking fish oil capsules for their omega-3 fatty acids may not help to stave off heart disease and early death after all, a new Greek study has found.

In a review of 20 previous studies involving nearly 70,000 people, many of whom were heart patients, taking fish oil capsules did not appear to lower any of the study volunteers’ chances of a heart attack or stroke. Nor did they seem to lower the risk of early death from other causes.

Even in the studies in which patients got their extra omega-3s by eating more fish, there still appeared to be no benefit, the researchers report in the Journal of the American Medical Association.

"Overall, omega-3...supplementation was not associated with a lower risk of all-cause mortality, cardiac death, sudden death, myocardial infarction, or stroke," wrote the study team, who were led by Dr. Mosef Elisaf at the University Hospital of Ioannina.

Omega-3 fatty acids have long been touted as a simple way to help improve triglycerides – a type of fat in the blood -- lower blood pressure, and control heart rhythm problems. Doctors have never been able to explain how the fats work, though it’s been theorized that they help prevent blood from sticking in blood vessels.

Even the Heart and Stroke Foundation recommends that Canadians consume two to three servings of fish per week to reap the benefits of omega-3s.

But in recent years, some research has cast doubt on whether fish oil has any effect on heart attacks or strokes.

Earlier this year, a similar review based on 20,000 participants in previous trials found that omega-3 supplements had no effect on heart disease or death.

The current review looked at studies that randomly assigned participants to take omega-3 supplements or placebo pills. It also included two studies in which people got counselling about how to increase their consumption of omega-3-rich foods.

Researchers also looked at whether the increased use in recent years of statins, which are medications that lower cholesterol, or other medications might be masking the benefits of fish oils. But Elisaf and his team said that wasn't the case.

Elisaf and his team added that further studies will need to look at whether higher doses of omega-3s might be effective. But they say for now, the findings do not justify the use of omega-3 supplements regularly to prevent heart events.

“In conclusion, omega-3 (fatty acids) are not statistically significantly associated with major cardiovascular outcomes across various patient populations,” they write.

“Our findings do not justify the use of omega-3 as a structured intervention in everyday clinical practice or guidelines supporting dietary omega-3 (fatty acids) administration.”