Omega-3 fatty acids

Description

Omega-3 fatty acids are one of two groups of fatty acids—the omega-3s and the omega-6s—that are vital to human life. They are called essential fatty acids (EFAs), which the body cannot make but absolutely needs for normal growth and development. These fats must be supplied by diet. People living in industrialized western countries eat up to 30 times more omega-6 than omega-3 fatty acids, resulting in a relative deficiency of omega-3 fats. Omega-6 metabolic products (inflammatory prostaglandins, thromboxanes, and leukotrienes) are formed in excessive amounts causing allergic and inflammatory disorders and making the body more prone to heart attacks, strokes, and cancer . Eating diets rich in omega-3 acids or taking fish oil supplements can restore the balance between the two fatty acids and can possibly reverse these disease processes.

General use

Heart disease and stroke

The American Heart Association (AHA) has endorsed omega-3 fatty acids as good for the heart. The omega-3 oils increase the concentrations of good cholesterol (high density lipoproteins, HDL) while decreasing the concentrations of bad cholesterol (triglycerides). In addition, eating omega-3-rich food will result in a moderate decrease in total cholesterol level. In a clinical study of 38 women, flaxseed flour, which contains high amounts of omega-3 fatty acids, decreased total cholesterol level by 6.9% and LDL cholesterol by 14.7%. In addition, lipoprotein (a), which is associated with heart attacks in older women, decreased by almost 10%. Thus, omega-3 fatty acids are natural alternatives to estrogen in prevention of heart attacks in postmenopausal women.

Furthermore, omega-3 oils protect the heart by preventing blood clots or keeping other fats from injuring the arterial walls. They not only relax arteries but also help to decrease constriction of arteries and thickening of blood.

Hundreds of studies have shown that diets rich in omega-3 fatty acids decrease risk of heart attacks, strokes, and abnormal heart rhythms. Eskimos, who eat a lot of cold-water fish, have low rates of heart attacks and strokes, possibly because they have thinner blood, high HDL to LDL cholesterol ratio, and less buildup of fatty deposits (plaques) in the arteries. Two clinical trials have shown that regular consumption of fish or fish-oil supplements can prevent sudden deaths due to abnormal heart rhythms. In the Diet and Reinfarction Trial (DART) of 2,033 men who previously suffered a heart attack , men who ate two to three servings of fatty fish a week had their risk of sudden cardiac death lowered by 29% compared to those who had a low fat or high fiber diet. In the Physician's Health Study of 20,551 doctors, a 52% reduction in risk of heart attacks was observed in those who ate at least one fish meal per week compared with those who ate fish once a month or less.

Mild hypertension

Several studies have shown that eating 200 g of fatty fish or taking six to 10 capsules of fish oil daily will lower blood pressure (BP). Therefore, omega-3 can benefit patients with borderline high blood pressure. Omega-3 oils also effectively prevent hypertension in cardiac patients after transplantation.

Supplement for newborns and babies

Omega-3 fatty acids are essential for normal development of vision and brain function, especially in newborns and children. Very low birth weight pre-term infants often have poor vision and motor skills, possibly because they receive less than one-third of the amount of omega-3 fatty acids outside the mother's womb that they would have received as a fetus. Human breast milk contains the appropriate amount of omega-3 and -6 fats and is believed best for babies. If mother's milk is unavailable, formulas with soybean oil that provide higher amounts of omega-3 fatty acids are more beneficial than those made from cow milk. Even full-term babies benefit from the addition of essential fatty acids to cow-milk formulas. Studies have shown that babies given formulas supplemented with EFAs have better vision and score higher in skills and problem-solving tests compared to babies on formulas that do not contain additional EFAs.

Rheumatoid arthritis

Because omega-3 fatty acids inhibit the action of inflammatory prostaglandins and leukotrienes, they can help control arthritis symptoms. Significant reduction in the number of tender joints and morning stiffness, as well as an increase in grip strength, have been observed in patients taking fish oil capsules. Studies have shown that patients taking fish oil supplements for rheumatoid arthritis require fewer pain medications; some are able to discontinue their nonsteroidal anti-inflammatory treatment. Despite the beneficial effects of omega-3 fats, regular antirheumatic drugs and nonsteroidal anti-inflammatory medications most likely still are required to control this chronic condition.

Diabetes

Early studies in laboratories indicate that omega-3 fatty acids in fish oils might prolong life in people with automimmune disorders like diabetes. A new study looked at substituting fish oil for corn oil in diets and found a tendency to suppress immune system dysfunction and prolong life. More studies are required to prove the diet's benefits in humans.

Inflammatory bowel disease

High-dose fish-oil supplements have shown to decrease abdominal cramping, diarrhea , and pain associated with Crohn's disease . In one study of 96 patients, patients who received 4.5 g of omega-3 fatty acids (15 fish oil capsules) required significantly less steroids to control symptoms. In another study of 78 Crohn's disease patients, 59% of patients who received nine fish oil capsules (2.7g of omega-3 fatty acids) daily did not have any disease flare-ups for at least one year compared to 26% recurrence rate in patients who were not given fish oil. Omega-3 fatty acids also are effective in preventing reappearance of Crohn's disease after surgery to remove sections of diseased bowel. In a clinical trial involving 50 patients, patients who received 2.7 grams of omega-3 fats as fish oil cut their rate of disease reappearance in half compared to patients receiving placebo. However, the effectiveness of omega-3 oils varies depending on the type of omega-3 oils being used, length of use, and the patient's diet.

Asthma

Taking high dose omega-3 fatty acids can reduce inflammation of the airways and reduce asthma attacks. According to Donald Rudin, the author of the book titled Omega-3 Oils, allergic disorders such as asthma may be triggered by too much omega-6 and too little omega-3 fats in our body. Excessive amounts of omega-6 prostaglandins cause the body to produce antibodies that cause allergic reactions. Flaxseed or fish oil supplements can keep the omega-6 fats in check and decrease the inflammatory reactions associated with asthma.

Berger's disease (Immunoglobulin A nephropathy)

Omega-3 fats may be effective in treating this autoimmune disease in which kidney function fails over time with few treatment options available. In a large, randomized study of 150 patients, those who received 3 g of omega-3 fatty acids daily for two years had significantly less reduction in renal function than those treated with placebo. Therefore, omega-3 fatty acids appear to have protective effects and may stabilize renal function in these patients.

Raynaud's disease

There have been few studies evaluating the effects of omega-3 fatty acids in treating Raynaud's disease; however, it appears that fish oil supplements may alleviate some blood clotting disorders.

Mental disorders

According to some studies, many common mental disorders, such as depression, bipolar disorder (manic-depression), attention-deficit hyperactive disorder (ADHD), anxiety , or schizophrenia , may be triggered by deficiencies of omega-3 fatty acids and/or B vitamins. The rates of depression are low in countries that eat a lot of fish, while the rate of depression steadily rises in the United States as Americans eat increasingly more processed food and less fresh fish and vegetables containing omega-3 fats. In one study, 53% of bipolar patients on placebo (olive oil) became ill again within four months, while none of the patients who were given 9.6 g daily of omega-3 fatty acids (as fish oil) did. Supplements containing omega-3 fats also reportedly have been effective in children with ADHD precipitated by essential fatty acid deficiencies. Furthermore, a 25% decrease in schizophrenic symptoms was observed in patients receiving eicosapentanoic acid (EPA), one of the omega-3 fatty acids contained in fish oil.

A report in 2001 revealed that omega-3 fatty acids may have effects on stabilizing mood and relieving depression. As studies continue, researchers are finding it more and more evident that omega-3 fatty acids can be effective for treating depression, though they still are un-certain exactly how they work. A 2003 report linked depression to increased risk of sudden cardiac death.

Acquired Immunodeficiency syndrome (AIDS)

In a small study of 20 AIDS patients, those who received fish oil supplement at dosage of 10 g of omega-3 fatty acids per day for 30 days gained more weight (2.4 kg) and significantly lowered their concentrations of tumor necrosis factor, which is believed to cause wasting in AIDS patients, compared to those who did not.

Cancer prevention

Omega-3 fatty acids inhibit tumor growth when injected into animals. Flaxseed oil, which is a plant source of omega-3 fatty acids, has been shown to prevent cancer of the breast, colon and prostate. The Mediterranean diet , which is heart healthy, also can decrease risk of getting cancer. Omega-3 fats, it seems, strengthen the immune systems and inhibit the inflammation and blood circulation of the tumors.

Preparations

Omega-3 fatty acids can be found naturally in the oil of cold-water fish, such as mackerel, salmon, sardines, anchovies, and tuna, or as extracted oils from plants, such as flaxseed , canola (rapeseed), or soybean. As of 2001, the U.S. Food and Nutrition Board had not issued the recommended daily allowance (RDA) for omega-3 fatty acids. However, researchers suggest that 100-200 mg daily of docosahexaenoic acid (DHA) and 200-400 mg daily of eicosapentanoic acid (EPA) were adequate for the majority of adults. The best way to achieve this dietary requirement is by eating fatty fish two or three times a week and/or eating vegetables and oils containing omega-3 fatty acids. If fish oil supplement is preferred, then one to two capsules a day is sufficient. Each 1 g fish oil capsule normally contains 180 mg of EPA and 120 mg of DHA. Vitamin E is often contained in fish oil supplements to prevent spoilage and vitamin-E deficiency, which may occur with high dose fish-oil consumption. Patients should take supplements containing omega-3 fatty acids only under professional supervision to prevent overdosage, adverse reactions, or interactions with other medications. For treatment of diseases, flaxseed oil should be the first choice because it is the richest source of omega-3 fatty acids, relatively safe, and inexpensive.

Precautions

The safest and most effective way to get omega-3 fatty acids is through diets of at least three fish meals a week. Fish-oil or flaxseed supplements should be taken only under a physician's supervision.

Although fish oils can be helpful in relieving arthritic symptoms, patients still may need anti-inflammatory medications to adequately control the disease.

Taking any medication during pregnancy is not recommended. Women who are pregnant or breastfeeding should talk to doctors before taking fish-oil supplements or any other medications.

Because of its blood thinning activity, those who are on aspirins, nonsteroidal anti-inflammatory drugs (NSAIDS), warfarin, or other anti-clotting medications must consult a physician before using the supplements.

Side effects

Consuming excessive amounts of fish-oil capsules can result in excessive bleeding, gastrointestinal distress, anemia , or strokes.

Interactions

Because of its blood-thinning activity, fish oil supplements may interact with aspirins, nonsteroidal anti-inflammatory drugs (NSAIDS), warfarin, or other anti-clotting medications to cause excessive bleeding.

Resources

BOOKS

Bloomfield, Harold H. Healing Anxiety with Herbs. New York, NY: HarperCollins Publishers, Inc., 1998.

Feinstein, Alice. Prevention's Healing with Vitamins: The Most Effective Vitamin and Mineral Treatments for Everyday Health Problems and Serious Disease–From Allergies and Arthritis to Water Retention and Wrinkles. Emmaus, PA: Rodale Press, Inc., 1996.

Rudin, Donald, and Clara Felix. Omega-3 Oils: To Improve Mental health, Fight Degenerative Diseases, and Extend your Life. Garden City Park, NY: Avery Publishing Group, 1996.

White, Linda B., and Sunny Mavor. Kids, Herbs, Health: A Parents' Guide to Natural Remedies. Loveland, CO: Interweave Press, 1998.

PERIODICALS

"AHA Endorsement Boosts Omega-3 Usage." Food Ingredient News (April 2003).

Belluzzi, A., Stefano Boschi, Corrado Brignola, et al. "Polyunsaturated Fatty Acids and Inflammatory Bowel Disease." American Journal of Clinical Nutrition. 71 suppl (2000): 339S-42S.

Christensen, Jeppe Hagstrup, Eva Korup, Jens Aare, et al. "Fish Consumption, n-3 Fatty Acids in Cell Membranes, and Heart Rate Variability in Survivors of Myocardial Infarction with Left Ventricular Dysfunction." American Journal of Cardiolology 79 (June 15, 1997): 1670-2.

Donadio, James V. "Use of Fish Oil to Treat Patients with Immunoglobulin A Nephropathy." American Journal of Clinical Nutrition 71 suppl (2000): 373S-5S.

Harrison, Roger, and Michael Burr. "Diets Containing Oil-rich Fish Confers More Benefits than Some Pharmacological Regimens." eBMJ. 317 (1998): 1152a. http://www.bmj.com/cgi/content/full/317/7166/1152/a.

Kremer, Joel M. "n-3 Fatty Acid Supplements in Rheumatoid Arthritis." American Journal of Clinical Nutrition 71 suppl (2000): 349S-51S.

Nichols, Sonia. "Fish Oil Diets Extend Survival in Autoimmune-Prone Mice." Diabetes Week (November 26, 2001): 3.

"Omega-3 Fatty Acids in the Treatment of Depression." Harvard Mental Health Letter (October 2001).

Oommen, Tom. "Fish Oil and Cardio Protection: Herrings & Red Herrings." eBMJ 317 (1998):1152a. http://www.bmj.com/cgi/eletters/317/7166/1152.

Prichard, B.N.C., C.C.T. Smith, K.L.E. Ling, et al. "Fish Oils and Cardiovascular Disease." eBMJ 310 (April 1, 1995): 819-820. http://www.bmj.com/cgi/content/full/310/6983/819.

Simopoulos, Artemis P. "Essential Fatty Acids in Health and Chronic Disease." American Journal of Clinical Nutrition 70 suppl (1999): 560S-9S.

Willatts, P., J.S. Forsyth, M.K.D. DiModugno, et al. "Effect of Long Chain Polyunsaturated Fatty Acids in Infant Formula on Problem Solving at 10 months of Age." Lancet 352 (Aug 29, 1998): 688-691.

ORGANIZATIONS

American Association of Naturopathic Physicians (AANP). 601 Valley Street, Suite 105, Seattle, WA 98109. (206) 298-0125. http://www.naturopathic.org.

OTHER

Adam.com News. "Fish Fights Fatal Heart Attack." Adam.com. JAMA. 279 no.1 (1998): 23-28. http://www.adam.com/. (March 6, 2000).

Gassull, MA. "Dietary Lipids in Inflammatory Bowel Disease: Are They of Therapeutic Use?" Medscape. Research and Clinical Forums. 20 no.1 (1998): 197-201. http://www.medscape.com/WellsMedical/RCF/1998/v20.n01/rcf2001.23.gass/. (March 7, 2000).

Grazian, Frank. "Fish Oil Aids Psychiatric Disorders." Alternative Health News Online. http://www.altmedicine.com/. (March 7, 2000).

Graboys, Thomas B. ldquo;Angina Pectoris: Management Strategies and Guide to Interventions. Chapter 16: Dietary Recommendations." Medscape. http://www.medscape.com/PCI/angina/angina.ch16/angina.ch16_01.html. (March 7, 2000).

Moser, Marvin. "Clinical Management of Hypertension. Chapter 3: Lifestyle Modifications in the Management of Hypertension." Medscape. http://medscape.com/clinicalmanagement-hypertension.ch03.html. (March 7, 2000).

Rutz, Dan. "Researchers: Fat in the diet may affect mental ability." CNN Interactive. (September 4, 1996). http://cnn.com/HEALTH/9809/04/fat.brains/index.html

Science briefs. "Flaxseed Lowers Cholesterol." Nutrition Science News online. Nutr Res. 18 no.7 (July 1998):1203-14. http://www.nutritionscience.com. (March 6, 2000).

"The Importance of Omega-3 Fatty Acids for Adults and Children." Flax Nutrition. http://www.flaxcouncil.ca/flaxnut11.htm. (March 7, 2000).

Teresa G. Odle

Omega-3 Fatty Acids

Definition

Purpose

Description

Recommended dosage

Precautions

Side effects

Interactions

Resources

Definition

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.

Purpose

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

Description

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

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

In fact, numerous studies show that a diet rich in omega-3 fatty acids not only lowers bad cholesterol, known as LDL, but also lowers triglycerides, the fatty material that circulates in the blood. Interestingly, researchers have found that the cholesterol levels of Inuit Eskimos tend to be quite good, despite the fact that they have a high fat diet. The reason for this, research has found, is that their diet is high in fatty fish, which is loaded with omega-3 fatty acids. The same has often been said about the typical Mediterranean-style diet.

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

Precautions

In early 2004, the U.S. Food and Drug Administration along with the the Environmental Protection Agency issued a statement that women who are or may be pregnant, as well as breastfeeding mothers and children, should avoid eating some types of fish thought to contain high levels of mercury. Fish that typically contain high levels of mercury are shark, swordfish, and mackerel, whereas shrimp, canned light tuna, salmon, and catfish are generally thought to have low levels of mercury. Because many people engage in fishing as a hobby, women should be sure before they eat any fish caught by friends and family that the local stream or lake is considered low in mercury.

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.

Interactions

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.

Resources

PERIODICALS

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.

ORGANIZATION

American Cancer Society. ‘‘Is Salmon Safe?’’ American Cancer Society.28 Jan 2004 American Cancer Society. 24 Feb 2005 <http://www.cancer.org/.>

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

Health and Age. ‘‘Omega-3 Fatty Acids.’’ Health and Age.2005 [cited 22 Feb 2005]. <http://www.healthandage.com/html/res/com/ConsSupplements/Omega3FattyAcidscs.html.>

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 <http://www.americanheart.org>

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 <http://www.cfsan.fda.gov/~dms/admehg3.html.>

Lee Ann Paradise

Omega-3 Fatty Acids

Definition

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.

Purpose

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

Description

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

Two types of omega-3 fatty acids are eicosapentaenoic 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, alphalinolenic 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

In fact, numerous studies show that a diet rich in omega-3 fatty acids not only lowers bad cholesterol, known as LDL, but also lowers triglycerides, the fatty material that circulates in the blood. Interestingly, researchers have found that the cholesterol levels of Inuit Eskimos tend to be quite good, despite the fact that they have a high fat diet. The reason for this, research has found, is that their diet is high in fatty fish, which is loaded with omega-3 fatty acids. The same has often been said about the typical Mediterranean-style diet.

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 biphenyls 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
• 1 1/2 teaspoons of flaxseeds = 3 grams of omega-3 fatty acids

Precautions

In early 2004, the U.S. Food and Drug Administration along with the the Environmental Protection Agency issued a statement that women who are or may be pregnant, as well as breastfeeding mothers and children, should avoid eating some types of fish thought to contain high levels of mercury. Fish that typically contain high levels of mercury are shark, swordfish, and mackerel, whereas shrimp, canned light tuna, salmon, and catfish are generally thought to have low levels of mercury. Because many people engage in fishing as a hobby, women should be sure before they eat any fish caught by friends and family that the local stream or lake is considered low in mercury.

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.

Interactions

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.

Resources

PERIODICALS

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.

ORGANIZATION

American Cancer Society. "Is Salmon Safe?" American Cancer Society 28 Jan 2004 American Cancer Society. 24 Feb 2005 〈http://www.cancer.org/〉.

American Heart Association. "American Heart Association Recommendation: Fish and Omega-3 Fatty Acids." American Heart Association 2005 American Heart Association. 22 Feb 2005 〈http://www.americanheart.org/〉.

Health and Age. "Omega-3 Fatty Acids." Health and Age 2005 [cited 22 Feb 2005]. 〈http://www.healthandage.com/html/res/com/ConsSupplements/Omega3FattyAcidscs.html〉.

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 〈http://www.americanheart.org/〉.

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 〈http://www.cfsan.fda.gov/∼dms/admehg3.html〉.

Omega-3 and Omega-6 Fatty acids

Fatty acids are organic compounds composed of carbon chains of varying lengths, with an acid group on one end and hydrogen bound to all the carbons of the chain. Essential fatty acids (EFAs) are those that are necessary for health, but cannot be synthesized by the body. Therefore, it is important to supply the body with EFAs through one's daily dietary intake. EFAs are also called vitamin F or polyunsaturates. They are important ingredients for the growth and maintenance of cells. The body utilizes essential fatty acids for hormone production, specifically for the production of prostaglandins , which aid in reducing hypertension , migraine headaches, and arthritis .

Essential fatty acids offer many positive effects for the body, including the nourishment of skin and hair; reduction of blood pressure , cholesterol , and triglyceride levels; prevention of arthritis and inflammation; and the reduction of the risk of blood clotting . Furthermore, essential fatty acids help protect the body from cardiovascular disease, candidiasis , eczema , and psoriasis , and they play a critical role in brain development and in the transmission of nerve impulses.

Types of EFAs

There are basically two types of essential fatty acids, omega-3 fatty acids, also known as linolenic acids, and omega-6 fatty acids, which are also called linoleic acids. The two types are distinguished by their chemical structures. Omega-3 EFAs are found in deepwater fish, fish oil, and some vegetable oils, such as canola, flaxseed, and walnut oil. Nuts are also a good source of omega-3 fatty acids, particularly hazelnuts, almonds, pecans, cashews, walnuts, and macadamia nuts. The best fish oil sources are salmon, mackerel, anchovies, sardines, and herring, which have a high fat content and provide more omega-3 than other fish. Flaxseeds are also a good source, and they are low in saturated fats and calories and have no cholesterol. Omega-6 fatty acids are found in raw nuts, seeds, legumes , and in unsaturated vegetable oils, such as borage oil, grape seed oil, primrose oil, sesame oil, and soybean oil.

Benefits of EFAs

There are many health benefits attributable to essential fatty acids. Research has shown that diets rich in monounsaturated fatty acids, which contain the omega-3 variety, reduce total mortality by 70 percent in patients who have already experienced a heart attack . This has led to a general recommendation to consume at least one meal a week of fish rich in omega-3 fatty acids. It is generally accepted that omega-3 fatty acids help to reduce the levels of triglycerides in the body, thus decreasing the risk of heart disease .

Omega-6 fatty acids have been shown to be beneficial in the reduction of cholesterol levels when they are substituted for saturated fats in a person's diet . The benefit in consuming omega-6 fatty acids therefore lies in the fact that they reduce the incidence of coronary artery disease, which is a condition where excess cholesterol builds up on the arteries of the heart, eventually blocking the flow of blood and causing a heart attack.

see also Fats; Heart Disease; Lipid Profile.

Susan S. KimJeffrey Radecki

Bibliography

Masley, Steven C. (1998). "Dietary Therapy for Preventing and Treating Coronary Artery Disease." American Family Physician 57:1299–1305. Also available from <http://www.aafp.org>

Sizer, Frances, and Whitney, Eleanor (2000). Nutrition: Concepts and Controversies, 8th edition. Stamford CT: Wadsworth/Thomson Learning.

omega‐3 fatty acids, omega‐6 fatty acids, or omega‐9 fatty acids (ω3 fatty acids, ω6 fatty acids, or ω9 fatty acids) Three series of long‐chain polyunsaturated fatty acids derived respectively from linolenic, linoleic, and oleic acids. Omega (ω) or n being the position of the first double bond counting from the terminal methyl group.