Epidemiologic and clinical trials have shown that omega-3 fatty acids reduce CVD incidence. Large-scale epidemiologic studies suggest that people at risk for coronary heart disease benefit from consuming omega-3 fatty acids from plants and marine sources. The ideal amount to take isn’t clear. Evidence from prospective secondary prevention studies suggests that taking EPA+DHA ranging from 0.5 to 1.8 grams per day (either as fatty fish or supplements) significantly reduces deaths from heart disease and all causes. For alpha-linolenic acid, a total intake of 1.5–3 grams per day seems beneficial. These data support the 2000 AHA Dietary Guidelines recommendation to include at least two servings of fish (particularly fatty fish) per week.

Randomized clinical trials have shown that omega-3 fatty acid supplements can reduce cardiovascular events (death, non-fatal heart attacks, non-fatal strokes). They can also slow the progression of atherosclerosis in coronary patients. However, more studies are needed to confirm and further define the health benefits of omega-3 fatty acid supplements for preventing a first or subsequent cardiovascular event. For example, placebo-controlled, double-blind, randomized clinical trials are needed to document the safety and efficacy of omega-3 fatty acid supplements in high-risk patients (those with type 2 diabetes, dyslipidemia, hypertension and smokers) and coronary patients on drug therapy. Mechanistic studies on their apparent effects on sudden death also are needed.

Healthy people should get their omega-3 fatty acids from fish and plant sources to protect their hearts, according to an updated report in Circulation: Journal of the American Heart Association by Penny Kris-Etherton, Ph.D., R.D., lead author along with co-authors William S. Harris, Ph.D., and Lawrence J. Appel, M.D., M.P.H. The comprehensive report examines the health benefits of omega-3 fatty acids in the context of cardiovascular disease (CVD) risk reduction and considers the recent Environmental Protection Agency and the Food and Drug Administration (FDA) guidance about the presence of contaminants in certain species of fish.

Since 2000, the American Heart Association’s dietary guidelines have recommended that healthy adults eat at least two servings of fish per week, particularly fish such as mackerel, lake trout, herring, sardines, albacore tuna and salmon. These fish contain two omega-3 fatty acids known as eicosapentaenoic and docosahexaenoic acids (EPA and DHA). A third kind, alpha-linolenic acid, is less potent. It comes from soybeans, canola, walnut and flaxseed and oils made from those beans, nuts and seeds.

People who have elevated triglycerides may need 2 to 4 grams of EPA and DHA per day provided as a supplement.  Even the 1gram/day dose recommended for patients with existing CVD may be more than can readily be achieved through diet alone. These people should consult their physician to discuss taking supplements to reduce heart disease risk. Patients taking more than 3 grams of omega-3 fatty acids from supplements should do so only under a physician’s care. The FDA has noted that high intakes could cause excessive bleeding in some people.

Depending on their stage of life, consumers need to be aware of both the benefits and risks of eating fish. Children and pregnant and nursing women may be at increased risk of exposure to excessive mercury from fish but also are generally at low risk for CVD. Thus, avoiding potentially contaminated fish is a higher priority for these groups. A brochure targeted at pregnant women is available at http://www.epa.gov/waterscience/fish/MethylmercuryBrochure.pdf