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An international consortium combined findings from a number of large studies that included data on levels of omega-3 fatty acids in the tissue or blood and examined the association with heart disease over time.

The epidemiological study, conducted by the Fatty acids and Outcomes Research Consortium (FORCE), found that higher consumption of plant and seafood-based omega-3s was moderately linked to a lower risk of dying from a heart attack.

Omega-3 fatty acids can be found in fish, with levels most abundant in salmon, trout, anchovies, sardines and herring, according to the U.S. Department of Agriculture’s National Nutrient Database. Plant-based omega-2s can be found in certain nuts and oils such as walnuts, flaxseed oil and canola oil. The researchers, led by Liana C. Del Gobbo, Ph.D., a postdoctoral research fellow at Stanford University School of Medicine and senior author Dariush Mozaffarian, M.D., dean of the Friedman School of Nutrition Science and Policy at Tufts University, said that the findings support the idea that eating fish and omega-3 is an important part of a healthy diet, even though only some trials of fish oil supplements have shown benefits, while others have not.

Combined, the 19 studies centrally pooled in a meta-analysis involved 45,637 participants.  Over time, 7,973 of these people experienced a first heart attack, with 2,781 resulting in death. Patients with higher blood levels of both seafood and plant-based omega-3s were 10 percent less likely to have a fatal heart attack. For each standard deviation in levels of omega-3s the risk dropped, with those at the highest end of the spectrum seeing a decreased risk of 25 percent compared to those with the lowest levels. Interestingly, researchers did not link levels of fatty acid biomarkers to the likelihood of experiencing a nonfatal heart attack.  The authors say this might mean there is a more specific mechanism for why omega-3 helps lower risk of death.

“These new results, including many studies which previously had not reported their findings, provide the most comprehensive picture to-date of how omega-3s may influence heart disease,” Del Gobbo said in a prepared statement.  She said that the findings were consistent after considering a variety of factors including age, sex, race, diabetes, or use of cholesterol-lowering medications.

“Most prior studies of dietary fats have relied on self-reported estimates of intake,” Mozaffarian said in a statement. “This new global consortium provides an unprecedented opportunity to understand how blood biomarkers of many different fats and fatty acids relate to diverse health outcomes and many additional investigations are in progress.”

The findings were published June 27, in Jama Internal Medicine.