Table of Contents


Essential to human health, omega-3 fatty acids are a form of polyunsaturated fats that are not made by the body and must be obtained from a person’s food.


Eating foods rich in omega-3 fatty acids is part of a healthy diet and helps people maintain their health.


In recent years, a great deal of attention has been placed on the value of eating a low fat diet. In some cases, people have taken this advice to the extreme by adopting a diet that is far too low in fat or, worse yet, a diet that has no fat at all. But the truth is that not all fat is bad. Although it is true that trans and saturated fats, which are found in high amounts in red meat, butter, whole milk, and some prepackaged foods, have been shown to raise a person’s total cholesterol, polyunsaturated fats can actually play a part in keeping cholesterol low. Two especially good fats are the omega-3

Mercury in fish

Least mercuryModerate mercury (eat 3 servings or less per month)Highest level (Avoid eating)
AnchoviesBluefishMackerel (king)
ClamsMackerel (Spanish, Gulf)Orange Roughy
Crab (domestic)Sea Bass (Chilean)Shark
FlounderTuna (canned albacore)Swordfish
Haddock (Atlantic)Tuna (yellowfin)Tilefish
Mackerel (N. Atlantic, chub)  
Perch (ocean) 
Salmon (canned)  
Salmon (fresh)  
Shad (American)
Sole (Pacific)
Squid (calamari)
Trout (freshwater)

SOURCE: National Resources Defense Council

(Illustration by GGS Information Services/Thomson Gale.)

Sources of Omega 6-Fatty Acids

  • Baked goods
  • Brazil nuts
  • Cereals
  • Corn oil
  • Cottonseed oil
  • Eggs
  • Hemp oil
  • Meats from grass-fed animals
  • Pecans
  • Pine nuts
  • Pumpkin oil
  • Safflower oil
  • Sesame oil
  • Soybean oil
  • Sunflower oil
  • Sunflower seeds
  • Wheat germ oil
  • Whole grains

(Illustration by GGS Information Services/Thomson Gale.)

fatty acids and the omega-6 fatty acids, which are polyunsaturated.

Two types of omega-3 fatty acids are eicosapentae-noic acid (EPA) and docosahexanoic acid (DHA), which are found mainly in oily cold-water fish, such as tuna, salmon, trout, herring, sardines, bass, swordfish, and mackerel. With the exception of seaweed, most plants do not contain EPA or DHA. However, alpha-linolenic acid (ALA), which is another kind of omega-3 fatty acid, is found in dark green leafy vegetables, flaxseed oil, fish oil, and canola oil, as well as nuts and beans, such as walnuts and soybeans. Enzymes in a person’s body can convert ALA to EPA and DHA, which are the two kinds of omega-3 fatty acids easily utilized by the body.

Many experts agree that it is important to maintain a healthy balance between omega-3 fatty acids and omega-6 fatty acids. As Dr. Penny Kris-Etherton and her colleagues reported in their article published in the American Journal of Nutrition an over consumption of omega-6 fatty acids has resulted in an unhealthy dietary shift in the American diet. The authors point out that what used to be a 1:1 ratio between omega-3 and omega-6 fatty acids is now estimated to be a 10:1 ratio. This poses a problem, researchers say, because consuming some of the beneficial effects gained from omega-3 fatty acids are negated by an over consumption of omega-6 fatty acids. For example, omega-3 fatty acids have anti-inflammatory properties, whereas omega-6 fatty acids tend to promote inflammation. Cereals, whole grain bread, margarine, and vegetable oils, such as corn, peanut, and sunflower oil, are examples of omega-6 fatty acids. In addition, people consume a lot of omega-6 fatty acid simply by eating the meat of animals that were fed grain rich in omega-6. Some experts suggest that eating one to four times more omega-6 fatty acids than omega-3 fatty acids is a reasonable ratio. In other words, as dietitians often say, the key to a healthy diet is moderation and balance.

The health benefits of omega-3 fatty acids

There is strong evidence that omega-3 fatty acids protect a person against atherosclerosis and therefore against heart disease and stroke, as well as abnormal heart rhythms that cause sudden cardiac death, and possibly autoimmune disorders, such as lupus and rheumatoid arthritis. In fact, Drs. Dean Ornish and Mehmet Oz, renowned heart physicians, said in a 2002 article published in O Magazine that the benefits derived from consuming the proper daily dose of omega-3 fatty acids may help to reduce sudden cardiac death by as much as 50%. In fact, in an article published by American Family Physician, Dr. Maggie Covington, a clinical assistant professor at the University of Maryland, also emphasized the value of omega-3 fatty acids with regard to cardiovascular health and referred to one of the largest clinical trials to date, the GISSI-Prevenzione Trial, to illustrate her point. In the study, 11,324 patients with coronary heart disease were divided into four groups: one group received 300 mg of vitamin E, one group received 850 mg of omega-3 fatty acids, one group received the vitamin E and fatty acids, and one group served as the control group. After a little more than three years, ‘‘the group given omega-3 fatty acids only had a 45% reduction in sudden death and a 20% reduction in all-cause mortality,’’ as stated by Dr. Covington.

According to the American Heart Association (AHA), the ways in which omega-3 fatty acids may reduce cardiovascular disease are still being studied. However, the AHA indicates that research as shown that omega-3 fatty acids:

  • decrease the risk of arrthythmias, which can lead to sudden cardiac death
  • decrease triglyceride levels
  • decrease the growth rate of atherosclerotic plaque
  • lower blood pressure slightly

Said to reduce joint inflammation, omega-3 fatty acid supplements have been the focus of many studies attempting to validate its effectiveness in treating rheumatoid arthritis. According to a large body of research in the area, omega-3 fatty acid supplements are clearly effective in reducing the symptoms associated with rheumatoid arthritis, such as joint tenderness and stiffness. In some cases, a reduction in the amount of medication needed by rheumatoid arthritis patients has been noted.

More research needs to be done to substantiate the effectiveness of omega-3 fatty acids in treating eating disorders, attention deficit disorder, and depression. Some studies have indicated, for example, that children with behavioral problems and attention deficit disorder have lower than normal amounts of omega-3 fatty acids in their bodies. However, until there is more data in these very important areas of research, a conservative approach should be taken, especially when making changes to a child’s diet. Parents should to talk to their child’s pediatrician to ascertain if adding more omega-3 fatty acids to their child’s diet is appropriate. In addition, parents should take special care to avoid feeding their children fish high in mercury. A food list containing items rich in omega-3 fatty acids can be obtained from a licensed dietitian.

Mercury levels and concerns about safety

A great deal of media attention has been focused on the high mercury levels found in some types of fish. People concerned about fish consumption and mercury levels can review public releases on the subject issued by the U. S. Food and Drug Administration and the Environmental Protection Agency. Special precautions exist for children and pregnant or breastfeeding women. They are advised to avoid shark, mackerel, swordfish, and tilefish. However, both the U.S. Food and Drug Administration and the Environmental Protection Agency emphasis the importance of dietary fish. Fish, they caution, should not be eliminated from the diet. In fact, Robert Oh, M.D., stated in his 2005 article, which was published in The Journal of the American Board of Family Practice ‘‘with the potential health benefits of fish, women of childbearing age should be encouraged to eat 1 to 2 low-mercury fish meals per week.’’

Contaminants and concerns about safety

Other concerns regarding fish safety have also been reported. In 2004, Hites and colleagues assessed organic contaminants in salmon in an article published in Science.Their conclusion that farmed salmon had higher concentrations of polychlorinated biphen-yls than wild salmon prompted public concerns and a response from the American Cancer Society. Farmed fish in Europe was found to have higher levels of mercury than farmed salmon in North and South America; however, the American Cancer Society reminded the public that the ‘‘levels of toxins Hites and his colleagues found in the farmed salmon were still below what the U.S. Food and Drug Administration, which regulates food, considers hazardous.’’ The American Cancer Society still continues to promote a healthy, varied diet, which includes fish as a food source.

Recommended dosage

The AHA recommends that people eat two servings of fish, such as tuna or salmon, at least twice a week. A person with coronary heart disease, according to the AHA, should consume 1 gram of omega-3 fatty acids daily through food intake, most preferably through the consumption of fatty fish. The AHA also states that ‘‘people with elevated triglycerides may need 2 to 4 grams of EPA and DHA per day provided as a supplement,’’ which is available in liquid or capsule form. Ground or cracked flaxseed can easily be incorporated into a person’s diet by sprinkling it over salads, soup, and cereal.

Sources differ, but here are some general examples:

  • 3 ounces of pickled herring =1.2 grams of omega-3 fatty acids
  • 3 ounces of salmon =1.3 grams of omega-3 fatty acids
  • 3 ounces of halibut =1.0 grams of omega-3 fatty acids
  • 3 ounces of mackerel = 1.6 grams of omega-3 fatty acids
  • 11/2 teaspoons of flaxseeds = 3 grams of omega-3 fatty acids


Conflicting information exists whether it is safe for patients with macular degeneration to take omega-3 fatty acids in supplement form. Until more data becomes available, it is better for people with macular degeneration to receive their omega-3 fatty acids from the food they eat.

Side effects

Fish oil supplements can cause diarrhea and gas. Also, the fish oil capsules tend to have a fishy aftertaste.


Although there are no significant drug interactions associated with eating foods containing omega-3 fatty acids, patients who are being treated with blood-thinning medications should not take omega-3 fatty acid supplements without seeking the advice of their physicians. Excessive bleeding could result. For the same reason, some patients who plan to take more than 3 grams of omega-3 fatty acids in supplement form should first seek the approval of their physicians.



Albert, C. M., Hennekens, C. H., O’Donnell, C. J., et al. ‘‘Fish consumption and risk of sudden cardiac death.’’ Journal of the American Medical Association. 279 (1998): 23–28.

Covington, M. B. ‘‘Omega-3 fatty acids.’’ American Family Physician. 70 (2004): 133–140.

Harris, W. S. ‘‘N-3 fatty acids and serum lipoproteins: human studies.’’ American Journal of Clinical Nutrition. 65 (1997): 1645–1654.

Hites, R. A., Foran, J. A., Carpenter, D. O., et al. ‘‘Global assessment of organic contaminants in farmed salmon.’’ Science. 303 (1997): 226–229.

Kris-Etherton, P. M., Harris, W. S., Appel, L. J., and American Heart Association Nutrition Committee. ‘‘Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease.’’ Circulation. 106 (2003): 2747– 2757.

Kris-Etherton, P. M., Taylor, D. S., Yu-Poth, S., et al. ‘‘Polyunsaturated fatty acids in the food chain in the United States. ’’ American Journal of Clinical Nutrition. 71 (2000): 1795–1885.

Oh, R. ‘‘Practical applications of fish oil (omega-3 fatty acids) in primary.’’ The Journal of the American Board of Family Practice. 18 (2005): 28–36. Ornish, Dean, and Oz, Mehmet. ‘‘Caution: Strong at Heart.’’ O: The Oprah Magazine. November 2002:163–168.


American Cancer Society. ‘‘Is Salmon Safe?’’ American Cancer Society.28 Jan 2004 American Cancer Society. 24 Feb 2005 <>

American Heart Association. ‘‘American Heart Association Recommendation: Fish and Omega-3 Fatty Acids.’’ American Heart Association. 2005 American Heart Association. 22 Feb 2005 <>

Health and Age. ‘‘Omega-3 Fatty Acids.’’ Health and Age.2005 [cited 22 Feb 2005]. <>

Kris-Etherton, P. M., Harris, W. S., Appel, L. J., and American Heart Association Nutrition Committee. ‘‘American Heart Association Statement: New Guidelines Focus on Fish, Fish Oil, Omega-3 Fatty Acids.’’ American Heart Association. 18 November 2002 American Heart Association. 22 Feb 2005 <>

U.S. Food and Drug Administration. ‘‘What You Need to Know About Mercury in Fish and Shellfish.’’ U.S. Food and Drug Administration. March 2004 U.S. Food and Drug Administration. 22 Feb 2005 <>

Lee Ann Paradise