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Fish and Omega-3 Fatty Acids:Anti-Inflammatory Nutrition
American Heart Association Recommendations
Omega-3 fatty acids benefit the heart of healthy people, and those at high risk of — or who have — cardiovascular disease.
The American Heart Association recommends eating fish (particularly fatty fish) at least two times a week. Fish is a good source of protein and doesn’t have the high saturated fat that fatty meat products do. Fatty fish like mackerel, lake trout, herring, sardines, albacore tuna and salmon are high in two kinds of omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
The American Heart Association also recommends eating tofu and other forms of soybeans, canola, walnut and flaxseed, and their oils. These contain alpha-linolenic acid (LNA), which can become omega-3 fatty acid in the body. The extent of this modification is modest and controversial, however. More studies are needed to show a cause-and-effect relationship between alpha-linolenic acid and heart disease.
The table below is a good guide to use for consuming omega-3 fatty acids.
Summary of Recommendations for Omega-3 Fatty Acid Intake
- Patients without documented coronary heart disease (CHD): Should eat a variety of (preferably fatty) fish at least twice a week. Include oils and foods rich in alpha-linolenic acid (flaxseed, canola and soybean oils; flaxseed and walnuts).
- Patients with documented coronary heart disease: Should consume about 1 g of EPA+DHA per day, preferably from fatty fish. EPA+DHA in capsule form could be considered in consultation with the physician.
- Patients who have high triglycerides and need to lower them (very common in patients with Metabolic Syndrome and Type 2 Diabetes): Should consume 2 to 4 grams of EPA+DHA per day provided as capsules under a physician’s care.
- Patients taking more than 3 grams of omega-3 fatty acids from capsules should do so only under a physician’s care. High intakes could cause excessive bleeding in some people.
Background
In 1996 the American Heart Association released its Science Advisory, “Fish Consumption, Fish Oil, Lipids and Coronary Heart Disease.” Since then important new findings have been reported about the benefits of omega-3 fatty acids on cardiovascular disease. These include evidence from randomized, controlled clinical trials. New information has emerged about how omega-3 fatty acids affect heart function (including antiarrhythmic effects), hemodynamics (cardiac mechanics) and arterial endothelial function. These findings are outlined in our November 2002 Scientific Statement, “Fish Consumption, Fish Oil, Omega-3 Fatty Acids and Cardiovascular Disease.”
The ways that omega-3 fatty acids reduce Cardiovascular Disease risk are still being studied. However, research has shown that they:
- decrease risk of arrhythmias, which can lead to sudden cardiac death
- decrease triglyceride levels
- decrease growth rate of atherosclerotic plaque
- lower blood pressure (slightly)
What do epidemiological and observational studies show?
Epidemiologic and clinical trials have shown that omega-3 fatty acids reduce Cardiovascular Disease 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.
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, dyslipi
demia, hypertension and smokers) and coronary patients on drug therapy. Mechanistic studies on their apparent effects on sudden death also are needed.
Increasing omega-3 fatty acid intake through foods is preferable. However, coronary artery disease patients may not be able to get enough omega-3 by diet alone. These people may want to talk to their doctor about taking a supplement. Supplements also could help people with high triglycerides, who need even larger doses. The availability of high-quality omega-3 fatty acid supplements, free of contaminants, is an important prerequisite to their use.
Anti-inflammatory Effects Of Omega 3 Fatty Acid In Fish Oil Linked To Lowering Of Prostaglandin
Omega 3 fatty acids in dietary fish oil are reported to have anti-inflammatory and anti-thrombogenic (anti-clotting) and anti-arrhythmic effects in humans, but the biochemical basis for these beneficial health effects is not well understood. Now a University of Michigan biochemist reports that fish oil significantly diminishes the production and effectiveness of various prostaglandins, naturally occurring hormone-like substances that can accentuate inflammation and thrombosis.
Dr. William L. Smith described his findings and his presentation was part of the scientific program of the American Society for Biochemistry and Molecular Biology (ASBMB). Dietary fish oil causes its prostaglandin-lowering effects through three different mechanisms, says Dr. Smith.
First, much fewer prostaglandins are made from omega 3 fatty acids as compared to the other class of fatty acids in the body, the omega 6 family of fatty acids that originate in the diet from leafy vegetables and other plant sources.
Second, the omega 3 fatty acids compete with omega 6 fatty acids for the same binding site on the COX 1 enzyme that converts the omega 6 fatty acids to prostaglandin (which is why the COX 1 enzyme and its COX 2 cousin are the targets of anti-inflammatory drugs like ibuprofen). The more omega 3 fatty acids present to block the binding sites, the fewer omega 6 fatty acids are able to be converted to prostaglandin.
Third, although omega 3 fatty acids also are converted to prostaglandins, the prostaglandins formed from omega 3 are generally 2 to 50 times less active than those formed from the omega 6 fatty acids from dietary plants.
The biochemical basis of other benefits of dietary fish oil -- for example, omega 3 fatty acids' impact on neuronal development and visual acuity -- are probably due to effects on biochemical pathways regulating nerve transmission. Understanding the different pathways through which omega 3 works to convert prostaglandin helps explain why the plant-based omega 6 fatty acids don't simply provide the same benefits. Because of omega 3 fatty acids' known benefits to health, especially cardiovascular health, Dr. Smith's advice is simple: eat more fatty fish like wild caught Alaskan Salmon.