In 2000, the American Heart Association adopted new guidelines for dietary consumption of omega-3 fatty acids. The nonprofit organization, whose objective is to disseminate information about heart disease and stroke, based its position on evidence that omega-3 fatty acids — found naturally in many kinds of fish and in some plant and nut oils — helps lower the risk of cardiovascular disease and stroke.
Functions of Omega-3 Fatty Acids
Omega-3 fatty acids are polyunsaturated fatty acids essential for human health and development. There are two dietary sources of omega-3 fatty acids: marine foods and seeds and nuts. Salmon, herring, trout, bluefish and sardines contain eicosapentaenoic acid, or EPA, and docosahexaenoic acid, or DHA. Canola and flaxseed oils, flax seed and walnuts contain alpha-linolenic acid, or ALA. EPA and DHA predominate in the human retina and brain because they govern the activities of retinal cells and neurons. Omega-3 fatty acids promote cardiovascular health by reducing platelet aggregation and inflammation. Chronic or low-grade inflammation is a clinical feature of obesity, metabolic syndrome and diabetes — all of which are factors that increase the risk for heart disease and stroke.
The revised American Heart Association guidelines highlight the importance of a healthy diet and maintaining an optimum weight in reducing the risk for heart disease and stroke. The organization advises healthy individuals to consume two servings of fatty fish per week, and also recommends eating plant-derived foods rich in alpha-linolenic acid.
For individuals with a known history of coronary heart disease, meanwhile, the AHA advises taking around 1 total gram of EPA and DHA every day. This can be obtained from oily fish or fish-oil supplements, if your doctor approves.
Those with high triglyceride levels are advised to take 2 to 4 total g of EPA and DHA under a doctor's care — an intake that can lead to a 20- to 40-percent reduction in triglyceride levels, according to research published in 2003 in the journal "Arteriosclerosis, Thrombosis, and Vascular Biology." Researchers warn that taking higher doses f these omega-3 fatty acids may lead to excessive bleeding.
Fish Oil Supplements
According to study results reported in 2010 at the American Heart Association’s Scientific Sessions, taking omega-3 fatty acid in capsule form was not better than a placebo in managing atrial fibrillation, a risk for heart attack and strokes. Atrial fibrillation is an abnormal heartbeat in which the upper chambers of the heart quiver instead of beating effectively to move blood into the lower chambers.
One group of patients with atrial fibrillation received 4 g of omega-3 capsules per day, and another group received a placebo for 24 weeks. Researchers found that omega-3 supplementation was ineffective in treating atrial fibrillation.
The U.S. Environmental Protection Agency warns against excessive consumption of tuna, shark, swordfish, king mackerel and tilefish due to their high levels of mercury. Women who are pregnant or lactating and young children should avoid eating these fish altogether. The agency does note that eating two meals each week — about 12 ounces total — of seafood like salmon, catfish and shrimp is acceptable. Check with local authorities about the safety of fish caught in your area.