Omega-3 and Omega-6 Fatty Acids

Definition

Omega-3 and omega-6 fatty acids are long-chain fatty polyunsaturated fats (PUFAs) that are vital structural components of the membranes of every cell in the human body. Omega fatty acids are needed to support many body functions, but the body does not produce them; they must be obtained from dietary sources. The three main omega-3 fatty-acids are eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alphalinolenic acid (ALA). DHA and EPA are especially important to proper functioning of the brain, retina, and body organs such as the kidneys and liver.

Sources of essential fatty acids

Omega-3

Omega-6

SOURCE: Office of Dietary Supplements. National Institutes of Health. “Omega-3 Fatty Acids: Fact Sheet for Health Professionals.” https://ods.od.nih.gov/factsheets/Omega3FattyAcidsHealthProfessional/#h3 (accessed April 19, 2018).

Purpose

Omega-3 and omega-6 fatty acids are essential to human life and contribute to many biochemical processes in the body. As vital structural components of cell membranes, omega-3 fatty acids are involved in muscle relaxation and contraction, blood clotting, growth, digestion, fertility, cell division, and the movement of calcium and other substances in and out of cells. Omega fatty acids also help to stimulate skin and hair growth, maintain bone health, and regulate metabolism. DHA is found in the fatty membranes of the brain that surround nerve cells, providing protective and functional support.

Throughout the body, omega-3 and omega-6 fatty acids synthesize prostaglandins, hormone-like substances that assist in controlling functions such as blood pressure, blood clotting, digestive functions in the gastrointestinal tract, and the inflammatory process. Study results have shown that consuming good sources of fatty acids in the diet has been shown to reduce inflammation in certain disease conditions. The American Heart Association (AHA) reports that omega-3 fatty acids benefit the hearts of healthy people and those at high risk of cardiovascular disease. Research indicates that omega-3 fatty acids decrease the levels of triglycerides and reduce the risk of arrhythmias and abnormal heartbeats that can lead to sudden death.

Studies have shown that regularly consuming fish or fish oil supplements can help lower triglyceride levels in the blood, reduce blood pressure, slow the progression of atherosclerosis, and reduce the risk of heart attack, stroke, and sudden death among people with cardiovascular disease. Evidence suggest that the consumption of omega-3s by pregnant women, especially DHA, may improve infant health outcomes, especially visual and cognitive development.

Research studies have explored various effects of omega-3 and omega-6 fatty acids as nutritional therapy. The beneficial effects of fish oil to treat or prevent irregular heartbeat in older adults were reported in a long-term study published in Circulation, the journal of the American Heart Association, in 2012. Heart arrhythmias may result when electrical impulses cause the heart to beat irregularly, too rapidly, or too slowly. The study focused on atrial fibrillation (AF), which is an irregular and frequently rapid heart rate. Another study published in the Journal of the American Medical Association (JAMA) in 2012 found no link between omega-3 fatty acid supplementation and reduced risk of cardiovascular disease. PUFAs are also of great interest in nutritional therapy for diabetes, because diabetes is associated with high risk of cardiovascular complications. Research has shown that supplementation with omega-3 fatty acids lowers triglycerides and VLDL-cholesterol, but improvements in mortality have not been found in diabetes patients as a result of omega-3 supplementation. The role of omega-6 in this population is not known.

Omega-3 supplements are thought to be effective in reducing symptoms associated with rheumatoid arthritis (RA), including joint tenderness, pain, and stiffness as a result of severe inflammation. RA patients themselves have reported reductions in the amount of medication needed to control symptoms.

Description

Fats are molecules composed of two types of smaller molecules, glycerol and/or fatty acids. The three types of fats in the diet are saturated (including trans fats), monounsaturated, and polyunsaturated. In addition to serving as a food source, fatty acids are used in cooking and in the manufacture of products such as soaps and cosmetics.

Saturated fats, which are linked to heart disease, are also known as solid fats because they are generally not liquid at room temperature. Saturated fat is found in animal products such as meat and dairy products, including whole milk and full-fat cheese. Other sources of saturated fat include hydrogenated shortening, coconut oil, and palm oils.

Trans fatty acids (trans fats) are saturated fats that are formed by hydrogenation, which is the addition of hydrogen to vegetable oil. The original fat becomes more saturated and solidifies. This process is used to create foods such as stick margarine and shortening. Trans fats are found in some processed foods that use these ingredients, such as cookies and snack foods.

Omega fatty acids

The body cannot produce fatty acids but is able to convert dietary ALA to EPA and DHA. However, the amounts of EPA and DHA produced through conversion of ALA are minimal, and obtaining more from dietary sources is recommended. Fatty fish such as salmon and albacore tuna are rich in EPA and DHA. The richest source of ALA is flaxseed and pure flaxseed oil is available commercially. Other sources include walnuts, canola oil, green leafy vegetables (e.g., kale, spinach, collards, chard), nuts, and soybeans. Seafood (especially salmon, herring, mackeral, and sardines) is the best source of omega-3 fatty acids. The fish that produce omega-3 fatty acids must consume algae, so wild fish are known to have higher levels of omega-3 than farmed fish that may consume grain. Omega-3 fatty acids are available in the form of dietary supplements that contain flaxseed oil or fish oil.




Foods rich in omega-3 fatty acids.





Foods rich in omega-3 fatty acids.

Specific sources of omega-3s include:

Ratio of omega-3 to omega-6

Cereals, whole-grain breads, margarine, and vegetable oils such as corn, peanut, and sunflower oil are examples of omega-6 fatty acid sources. People can also obtain omega-6 fatty acids by eating meat from animals fed grains rich in omega-6. The ratio of omega-6s to omega-3s is not established, but since omega-6s sources are plentiful and are less apt to be in short supply in the body, it is preferable to consume omega-3s in a 2:1 to 4:1 ratio with omega-6s. Health experts agree that individuals will benefit most from consuming more foods containing omega-3s.

Sources of omega fatty acids

SEAFOOD. The American Heart Association (AHA) recommends that people consume fish at least twice a week. Preferred sources include fatty fish such as salmon, tuna, albacore tuna, herring, sardines, and mackerel. Increased intake of seafood is also recommended in the Dietary Guidelines for Americans issued by the U.S. Department of Agriculture (USDA) and the Department of Health and Human Services (HHS). The Guidelines advise adults to consume a total of 1,750 mg of EPA and DHA from eating 8 oz. of appropriate fish sources each week. Smaller amounts of seafood are recommended for children.

According to the Guidelines, some common seafood varieties and their EPA, DHA, and mercury contents include (per four ounce serving):

FLAXSEED. Flaxseed is the seed of the plant Linum usitatissimum. It is a rich source of ALA and also contains LA. Flaxseed is high in dietary fiber and lignans, phytochemicals that mimic the effect of the female hormone estrogen. Flaxseed oil is derived from pressed flaxseed. Flaxseed and flaxseed oil have different properties and nutritional values. According to the Flax Council of Canada, about 42% of the flaxseed is oil and more than 70% of that oil is polyunsaturated fat (PUFA). Of that fat content, 57% is ALA.

SUPPLEMENTS. Food is the preferred source of nutrients like omega fatty acids, and most people obtain more than an adequate intake of omega-6 fatty acids from food, but omega fatty acids are also available as dietary supplements. In the United States, omega-fatty acid in forms including fish oil and flaxseed supplements is consistently one of the top supplements taken for health reasons by adults and children. Omega-6 fatty acids are present in supplements such as evening primrose oil. The FDA recommends that consumers not take more than a total of 3 g per day of EPA and DHA omega-3 fatty acids, with no more than 2 g per day from a dietary supplement.

Recommended intake

Recommended daily allowances (RDAs) have not been established for fatty acids by the Food and Nutrition Board (FNB) at the U.S. Institute of Medicine (IOM) of the National Academies (formerly the National Academy of Science) as for other nutrients like vitamins and minerals. Adequate intake (AI) levels, however, have been established. AI is an estimate for suggested intake when not enough information is available to determine an RDA. The daily AI levels for omega-3 fatty acids are:

The daily AI levels for omega-6 fats are:

The AHA has separate guidelines for people with certain heart conditions. According to the AHA, people with coronary heart disease should consume 1 g of omega-3 fatty acids daily through food intake, preferably from fatty fish. People with high triglyceride levels in the blood may require doses up to 4 g, which may be obtained by taking supplements.

In agreement with AHA guidelines, the U.S. Food and Drug Administration (FDA) has permitted the use of a statement on labels for foods with omega-3s indicating that “supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease.”

KEY TERMS
Alpha-linolenicacid(ALA)—
Apolyunsaturatedomega-3 fatty acid found primarily in seed oils (canola oil, flaxseed oil, and walnut oil), purslane and other broad-leaved plants, and soybeans. ALA has been shown to reduce the risk of cardiovascular disease.
Atherosclerosis—
Development of plaque on the walls of the major blood vessels, causing narrowing of the vessels, blockages, and formation of blood clots. Vessel narrowing causes blood pressure to rise. Blockages and clots may lead to stroke, heart attack, other vascular issues, eye problems, and kidney problems.
Cardiovascular disease—
Clinical conditions involving the heart and vascular system (blood vessels), including angina, heart attacks, peripheral vascular disease, and stroke.
Cholesterol—
A waxy substance made by the liver and also acquired through diet. High levels in the blood may increase the risk of cardiovascular disease.
Dietary supplement—
A product, such as a vitamin, mineral, herb, amino acid, or enzyme, that is intended to supplement dietary sources when deficiency is noted.
Docosahexaenoic acid (DHA)—
A long-chain omega- 3 fatty acid found primarily in oily fish. DHA is important for brain function and health of the retina of the eye.
Essential fatty acid—
A type of fat that is necessary for proper organ function and that must be obtained from dietary sources because the body does not produce fatty acids.
Flaxseed—
Linseed; seed of flax, Linum usitatissimum, used as a dietary source of oil for treating inflammation of the respiratory, intestinal, and urinary tracts, and available as a dietary supplement.
Monounsaturated fat—
A fat or fatty acid with only one double-bonded carbon atom in its molecule. The most common monounsaturated fats are palmitoleic acid and oleic acid, found naturally in nuts and avocados. Oleic acid is the main component of olive oil.
Polyunsaturated fat—
A fatty acid molecule with two or more double bonds, known to be beneficial to health when consumed in moderate amounts. A type of fat found in some vegetable oils, such as sunflower, safflower, and canola oils.
Triglycerides—
A type of fat formed from glycerol and fatty acids, the main components of natural fats and oils. High levels of triglycerides in the blood may result from consumption of unhealthy fats and oils and may increase an individual's risk of coronary heart disease and stroke.

Precautions

Individuals are advised to discuss the need for supplementing omega fatty acids with their physicians before taking supplements. This is especially important for women who are pregnant or breastfeeding and people with chronic conditions such as cancer. Although the FDA views omega-3 dietary supplements from fish as “generally recognized as safe (GRAS),” supplements do not undergo the stringent testing for safety and effectiveness that is required for drugs.

Flaxseed, flaxseed oil, and fish and krill oils should be refrigerated to help maintain their effectiveness. Corn oil and some other oils may be made with genetically modified grains and individuals wishing to avoid GMOs are advised to seek non-GMO oils or to use organic products only.

QUESTIONS TO ASK YOUR DOCTOR

Interactions

People who take medications are advised to consult their doctors before taking any dietary supplements. Omega fatty acid supplements may increase the risk of bleeding in people who take anticoagulant or antiplatelet medications such as warfarin (Coumadin) or clopidogrel (Plavix). They may also interact with diabetes medications, antibiotics, hormone replacement therapy, and certain chemotherapy drugs used in cancer treatment.

Complications

Women diagnosed or at risk for hormone-sensitive breast or uterine cancer are advised to consult with their doctor before taking omega fatty acids as supplements. Men with or at high risk of prostate cancer should also consult with their physicians before taking these supplements. Omega fatty acids supplements, including flaxseed, may lower blood glucose levels, which is not advisable for individuals with diabetes.

Fish oil supplements may cause minor gastrointestinal upsets in some individuals, with symptoms such as diarrhea, heartburn, indigestion, and abdominal bloating.

Parental concerns

Pregnant or breastfeeding women should discuss fish consumption with their physicians due to the risk of mercury consumption.

See also Acne diet ; ADHD diet ; Anti-inflammatory diets ; Arthritis diet ; Cancer-fighting foods ; Coronary heart disease ; Diabetic diet ; Dietary supplements ; Greek and Middle Eastern diet ; Hamptons diet ; Mediterranean diet ; Menopause diet .

Resources

BOOKS

Alasalvar, Cesarettin, et al., eds. Handbook of Seafood Quality, Safety, and Health Applications. Ames, IA: Blackwell, 2010.

Hernandez, Ernesto M., and Masashi Hosokawa, editors. Omega-3 Oils: Applications in Functional Foods. Urbana, IL: AOCS, 2011.

Larsen, Laura, editor. Diet and Nutrition Sourcebook. Detroit: Omnigraphics, 2011.

Schlenker, Eleanor D. Williams' Essentials of Nutrition and Diet Therapy. St Louis: Elsevier/Mosby, 2011.

U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015–2020 Dietary Guidelines for Americans. 8th ed. December 2015. http://health.gov/dietaryguidelines/2015/guidelines/ (accessed May 1, 2018).

PERIODICALS

Borow, Kenneth M., R. Preston Mason, Krishnaswami Vijayaraghavan, et al. “Eicosapentaenoic Acid as a Potential Therapeutic Approach to Reduce Cardiovascular Risk in Patients with End-Stage Renal Disease on Hemodialysis: A Review.” Cardiorenal Medicine 8, no. 1 (December 2017): 18–30.

Jason H. Y. Wu, R. N. Lemaitre, I. B. King, et al. “Association of Plasma Phospholipid Long-Chain Omega-3 Fatty Acids with Incident Atrial Fibrillation in Older Adults: The Cardiovascular Health Study.” Circulation 125, no. 9. (March 6, 2012): 1048–93.

Jeppesen, Charlotte, Katja Schiller, Matthias B. Schulze, et al. “Omega-3 and Omega-6 Fatty Acids and Type 2 Diabetes.” Current Diabetes Report 13, no. 2 (2011): 279–88.

Manor I., A. Magen, D. Keidar, et al. “The Effect of Phosphatidylserine Containing Omega-3 FA on Attention-Deficit Hyperactivity Disorder Symptoms in Children: A Double-Blind Placebo-Controlled Trial, Followed by an Open-Label Extension.” European Psychiatry 27, no. 5. (July 2012): 335–42.

Murphy, Dan. “Evolutionary Aspects of Diet: The Omega-6/0mega-3 Ratio and the Brain.” American Chiropractor 34, no. 4. (April 2012): 26–28.

Stough, Con, Luke Downey, Beata Silber, et al. “The Effects of 90-Day Supplementation with the Omega-3 Essential Fatty Acid Docosahexaenoic Acid (DHA) on Cognitive Function and Visual Acuity in a Healthy Aging Population.” Neurobiology of Aging 33, no. 4 (April 2012): 824.e1–e3.

Sublette, M. Elizabeth, S. P. Ellis, A. L. Geant, et al. “Meta-Analysis: Effects of Eicosapentaenoic Acid in Clinical Trials in Depression.” Journal of Clinical Psychiatry 72, no. 12 (December 2011): 1577–84.

WEBSITES

American Heart Association. “Fish 101.” Heart.org . http://www.heart.org/HEARTORG/GettingHealthy/NutritionCenter/Fish-101_UCM_305986_Article.jsp (accessed May 12, 2018).

Mayo Clinic staff. “Health Tip: Fish Oil.” Mayo Clinic. http://www.mayoclinic.org/drugs-supplements-fishoil/art-20364810 (accessed May 12, 2018).

National Center for Complementary and Integrative Health. “Flax and Flaxseed Oil.” U.S. National Library of Medicine, National Institutes of Health. http://www.nccih.nih.gov/health/flaxseed/ataglance.htm (accessed May 12, 2018).

National Center for Health Statistics and National Center for Complementary and Integrative Health. “Omega-3 Supplements: An Introduction.” National Institutes of Health. http://nccih.nih.gov/health/omega3/introduction.htm (accessed May 12, 2018).

ORGANIZATIONS

Academy of Nutrition and Dietetics, 120 S. Riverside Plaza, Ste. 2190, Chicago, IL, 60606-6995, (312) 899-0040, (800) 877-1600, amacmunn@eatright.org, http://www.eatright.org .

American Heart Association, 7272 Greenville Ave., Dallas, TX, 75231, (888) 242-8883, help@onlineaha.org, https://www.onlineaha.org .

American Pregnancy Association, 3007 Greenway Cir. N, Ste. 800, Irving, TX, 75038, (800) 672-2296, info@americanpregnancy.org, http://www.americanpregnancy.org .

Flax Council of Canada, 465-167 Lombard Ave., Winnipeg, CanadaManitoba, MB R3B 0T6, 1(204) 982-2115, Fax: 1(204) 942-2128, flax@flaxcouncil.ca, http://www.flaxcouncil.ca .

International Fish Oil Standards, 120 Research Ln., Ste. 203, University of Guelph Research Park, Guelph Ontario, Canada, N1G 0B4, (519) 341-3367, (877) 557-7722, admin@nutrasource.ca, http://www.ifosprogram.com/IFOS .

National Center for Complementary and Integrative Health (NCCIH), 9000 Rockville Pike, NIH Campus, Bldg. 31, Bethesda, MD, 20892, (888) 644-3615, https://nccih.nih.gov/tools/emailnccih , https://nccih.nih.gov .

U.S. Food and Drug Administration (FDA), 10903 New Hampshire Ave., Silver Spring, MD, 20993, (888) 463-6332, https://www.fda.gov/AboutFDA/ContactFDA , https://www.fda.gov .

L. Lee Culvert
Revised by Liz Swain

  This information is not a tool for self-diagnosis or a substitute for professional care.