Omega-3 fatty acids may not reduce the risk for cardiovascular events, deaths from coronary heart disease (CHD), strokes, or cardiac arrhythmias, new research suggests.

A Cochrane systematic review that encompassed findings of 79 studies involving more than 112,000 people found no evidence that increasing consumption of alpha ­linolenic acid (ALA) and the long-chain omega-3 fatty acids (LCn3) eicosapentaenoic acid or docosahexaenoic acid enhances cardiovascular health or protects against all-cause death or cardiovascular events.

Low/moderate-quality evidence suggests that ALA may slightly reduce cardiovascular events, mortality, and arrhythmias, and high-quality evidence suggests that LCn3 may reduce triglycerides and increase high-density lipoprotein (HDL) cholesterol.

"Clinicians need to be aware that unless there is a specific need to reduce triglycerides, then there is no reason to encourage use of omega-3 supplements," lead author Lee Hooper, Ph.D., from the University of East Anglia, United Kingdom, and a member of the World Health Organization Nutrition Guidance Expert Advisory Group, told.

Previous Research Inconsistent

Many practice guidelines recommend omega-3 fats, in the form of fish oil or supplements, to enhance cardiovascular health; they are widely used for this purpose.

LCn3 is derived from fish, while ALA, a shorter-chain omega-3 fatty acid, comes from plant sources and is partially converted to LCn3 fatty acids within the body.

The authors suggest possible mechanisms for a protective role of omega-3 fats against cardiovascular disease (CVD), including lowering blood pressure, altering the lipid profile, modulating arterial lipoprotein lipase levels, reducing thrombosis, producing anti-inflammatory and anti-arrhythmic effects, improving vascular endothelial function and insulin sensitivity, and increasing plaque stability and paraoxonase levels.

Lifestyle Interventions

Ian Johnson, BSc, Ph.D., emeritus fellow, Quadram Institute Bioscience, Norwich, United Kingdom, who was not involved with the research, said that he was "quite surprised by the outcome of this systematic review" but is "confident that it is of high quality."

"Perhaps the general message is that for fatty acids, as for many other dietary constituents, it is very difficult to reproduce epidemiological findings using randomized intervention trials because human diets are immensely complex and physiological effect sizes for particular nutrients are small about the causation of chronic diseases," he said.

Hooper added, "I would love to see omega-3 supplements delivering what a simple way to reduce our cardiovascular risk. But they don't, so we need to focus on the lifestyle interventions that do work eating a high-quality diet, moderate alcohol, not smoking, and keeping fit and active."