• Fish, plant, and nut oils are the primary dietary source of omega-3 fatty acids.

• Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found in cold-water fish such as salmon, mackerel, halibut, sardines, tuna, and herring.

• ALA is found in flaxseeds, flaxseed oil, canola (rapeseed) oil, soybeans, soybean oil, pumpkin seeds, pumpkin seed oil, purslane, perilla seed oil, walnuts, and walnut oil.

• Other sources of omega-3 fatty acids include sea life such as krill and algae.

Available Forms

• In addition to the dietary sources described, EPA and DHA can be taken in the form of fish oil capsules. Flaxseed, flaxseed oil, fish and krill oils should be kept refrigerated. Whole flaxseeds must be ground within 24 hours of use, otherwise the ingredients lose their activity. Flaxseeds are also available in ground form in a special mylar package so that the components in the flaxseeds stay active.

• Be sure to buy omega-3 fatty acid supplements made by established companies who certify that their products are free of heavy metals such as mercury, lead, and cadmium.

How to Take It

• Dosing for fish oil supplements should be based on the amount of EPA and DHA in the product, not on the total amount of fish oil.

• Supplements vary in the amounts and ratios of EPA and DHA. A common amount of omega-3 fatty acids in fish oil capsules is 0.18 grams (180 mg) of EPA and 0.12 grams (120 mg) of DHA.

• Five grams of fish oil contains approximately 0.17 - 0.56 grams (170 -560 mg) of EPA and 0.072 - 0.31 grams (72 - 310 mg) of DHA.

• Different types of fish contain variable amounts of omega-3 fatty acids, and different types of nuts or oil contain variable amounts of a-linolenic acid. Fish oils contain approximately 9 calories per gram of oil.

Children (18 years and younger)

• The precise safe and effective doses of all types of omega-3 fatty acid supplements in children have not been established.

• Omega-3 fatty acids are used in some infant formulas, although effective doses are not clearly established. Ingestion of fresh fish should be limited in young children due to the presence of potentially harmful environmental contaminants, including mercury.

• Fish oil capsules should not be used in children except under the direction of a health care provider.

Adults

• Individuals taking more than 3 grams daily of omega-3 fatty acids from capsules should do so only under the supervision of a health care provider due to an increase risk of bleeding.

• For healthy adults with no history of heart disease: The American Heart Association (AHA) recommends eating fish at least 2 times per week.

• For adults with coronary heart disease: The American Heart Association (AHA) recommends an omega-3 fatty acid supplement (as fish oils), 1 gram daily of EPA and DHA. It may take 2 - 3 weeks for benefits of fish oil supplements to be seen.

• For adults with high cholesterol levels: The American Heart Association (AHA) recommends an omega-3 fatty acid supplement (as fish oils), 2 - 4 grams daily of EPA and DHA. It may take 2 - 3 weeks for benefits of fish oil supplements to be seen.

Precautions

Because of the potential for side effects and interactions with medications, dietary supplements should be taken only under the supervision of a knowledgeable health care provider.

Omega-3 fatty acids should be used cautiously by people who bruise easily, have a bleeding disorder, or take blood-thinning medications, including warfarin (Coumadin) or clopidogrel (Plavix), because excessive amounts of omega-3 fatty acids may lead to bleeding. In fact, people who eat more than three grams of omega-3 fatty acids per day (equivalent to 3 servings of fish per day) may be at an increased risk for hemorrhagic stroke, a potentially fatal condition in which an artery in the brain leaks or ruptures.

Fish oil can cause flatulence, bloating, belching, and diarrhea. Time-release preparations may reduce these side effects, however.

People with either diabetes or schizophrenia may lack the ability to convert alpha-linolenic acid (ALA) to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the forms more readily used in the body. Therefore, people with these conditions should obtain their omega-3 fatty acids from dietary sources rich in EPA and DHA. Also, individuals with type 2 diabetes may experience increases in fasting blood sugar levels while taking fish oil supplements. If you have type 2 diabetes, only use fish oil supplements under the supervision of a health care provider.

Although studies have found that regular consumption of fish (which includes the omega-3 fatty acids EPA and DHA) may reduce the risk of macular degeneration, a recent study including 2 large groups of men and women found that diets rich in ALA may substantially increase the risk of this disease. More research is needed in this area. Until this information becomes available, it is best for people with macular degeneration to obtain omega-3 fatty acids from sources of EPA and DHA, rather than ALA.

Similar to macular degeneration, fish and fish oil may protect against prostate cancer, but ALA may be associated with increased risk of prostate cancer in men. More research in this area is needed.

Fish (and fish oil supplements) may contain potentially harmful contaminants, such as heavy metals (including mercury), dioxins, and polychlorinated biphenyls (PCBs). For sport-caught fish, the U.S. Environmental Protection Agency (EPA) recommends that intake be limited in pregnant or nursing women to a single 6-ounce meal per week, and in young children to less than 2 ounces per week. For farm-raised, imported, or marine fish, the U.S. Food and Drug Administration recommends that pregnant or nursing women and young children avoid eating types with higher levels of mercury (such as mackerel, shark, swordfish, or tilefish), and less than 12 ounces per week of other fish types. Unrefined fish oil preparations may contain pesticides. 

Possible Interactions

If you are currently being treated with any of the following medications, you should not use omega-3 fatty acid supplements, including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linolenic acid (ALA), without first talking to your health care provider.

Blood-thinning medications -- Omega-3 fatty acids may increase the effects of blood thinning medications, including aspirin, warfarin (Coumadin), and clopedigrel (Plavix). While the combination of aspirin and omega-3 fatty acids may actually be helpful under certain circumstances (such as in heart disease), they should only be taken together under the guidance and supervision of a health care provider.

Blood sugar lowering medications -- Taking omega-3 fatty acid supplements may increase fasting blood sugar levels. Use with caution if taking blood sugar lowering medications, such as glipizide (Glucotrol and Glucotrol XL), glyburide (Micronase or Diabeta), glucophage (Metformin), or insulin, as omega-3 fatty acid supplements may increase your need for the medication(s).

Cyclosporine -- Taking omega-3 fatty acids during cyclosporine (Sandimmune) therapy may reduce toxic side effects, such as high blood pressure and kidney damage, associated with this medication in transplant patients.

Etretinate and topical steroids -- The addition of omega-3 fatty acids (specifically EPA) to the drug therapy etretinate (Tegison) and topical corticosteroids may improve symptoms of psoriasis.

Cholesterol-lowering medications -- Following certain nutritional guidelines, including increasing the amount of omega-3 fatty acids in your diet and reducing the omega-6 to omega-3 ratio, may allow a group of cholesterol lowering medications known as "statins", including atorvastatin (Liptor), lovastatin (Mevacor), and simvastatin (Zocor) to work more effectively.

Nonsteroidal anti-inflammatory drugs (NSAIDs) -- In an animal study, treatment with omega-3 fatty acids reduced the risk of ulcers from nonsteroidal anti-inflammatory drugs (NSAIDs), including ibuprofen (Motrin or Advil) and naproxen (Alleve or Naprosyn). More research is needed to evaluate whether omega-3 fatty acids would have the same effects in people.