Blood levels of seafood and plant-based omega-3 fatty acids are associated with a lower risk of dying from heart attacks, according to a new epidemiological study, published today in JAMA Internal Medicine, led by Liana C. Del Gobbo, Ph.D., a postdoctoral research fellow in the division of cardiovascular medicine at Stanford University School of Medicine and senior author Dariush Mozaffarian, M.D., Dr.P.H., dean of the Friedman School of Nutrition Science and Policy at Tufts University in Boston.
Researchers from around the world joined together to form the Fatty acids and Outcomes Research Consortium (FORCE). By pooling findings from diverse large studies that had measured blood or tissue levels of omega-3 fatty acids, they evaluated relationships with heart disease events over time. Each study performed new standardized, individual-level analyses. Findings were then centrally pooled in a meta-analysis.
A total of 19 studies were involved from 16 countries and including 45,637 participants. Of these, 7,973 people developed a first heart attack over time, including 2,781 deaths and 7,157 nonfatal heart attacks.
Overall, both plant and seafood-based omega-3s were associated with about a 10 percent lower risk of fatal heart attacks per standard deviation. People with the highest blood levels of omega-3s had about 25 percent lower risk of fatal heart attack, compared to people with the lowest levels. In contrast, these fatty acids biomarkers were generally not associated with a risk of nonfatal heart attacks, suggesting a more specific mechanism for benefits of omega-3s related to 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,” said Del Gobbo, who conducted this study as part of her postdoctoral work with Mozaffarian. “Across these diverse studies, findings were also consistent by age, sex, race, presence or absence of diabetes, and use of aspirin or cholesterol-lowering medications.”
“For the leading cause of death in the world, lowering the risk by about 25 percent would be quite meaningful. At a time when some but not other trials of fish oil supplementation have shown benefits, there is uncertainty about cardiovascular effects of omega-3s,” said Mozaffarian. “Our results lend support to the importance of fish and omega-3 consumption as part of a healthy diet.”
Fish is the major food source of omega-3 fatty acids, including eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA). According to the U.S. Department of Agriculture’s National Nutrient Database, fatty fish such as salmon, trout, anchovies, sardines, and herring contain the highest amounts of omega-3 fatty acids; although all fish contain some levels. In addition to omega-3 fatty acids, fish provide specific proteins, vitamin D, selenium, and other minerals and elements. Alpha-linolenic acid (ALA) is the plant-based omega-3 fatty acid found in walnuts, flaxseed oil, and canola oil and some other seed and nuts and their oils.
“Most prior studies of dietary fats have relied on self-reported estimates of intake,” said Mozaffarian. “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.”