Omega-3 Fatty Acids

Overview

Omega-3 (alpha-linolenic acid) is an essential fatty acid that is deficient in the diets of many Americans. In the late 1970s, scientists learned that the native Inuits in Greenland, who consumed a diet very high in omega-3 fatty acids, had surprisingly low rates of heart attacks. Since that time, more than 4,500 studies have been conducted in an attempt to understand the beneficial roles that the omega-3 fatty acids play in human metabolism and health.

Structurally, omega-3 contains 3 double bonds, which makes it a polyunsaturated fatty acid. This also makes omega-3 very susceptible to becoming rancid. Food processors remove it from food products in order to lengthen shelf life. Marine plants such as plankton are the primary source of omega-3 fatty acids in the food chain. Fish and other aquatic animals that feed on plankton, incorporate the omega-3 fatty acids into their tissues. The richest land source of omega-3 is the oil that is commercially expelled from flaxseeds. Alpha-linolenic acid gets converted in the body into longer-chain omega-3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Thus, the term omega-3 also refers to a family of omega-3 fatty acids, which includes alpha-linolenic acid, EPA, and DHA.

In England, the Task Force of the British Nutrition Foundation suggests a daily intake of omega-3 ranging from 0.5 to 2.5 percent of energy requirements. This corresponds to 1 to 6 grams daily for men and from 1 to 5 grams daily for women. (1)

Dosage Info

Dosage Range

Alpha linolenic acid (omega-3): 1-2 tablespoonsful daily.

Fish oils (EPA and DHA): 500-2,000mg daily.

Most Common Dosage

Alpha linolenic acid (omega-3): 1 tablespoonful daily.

Fish oils (EPA and DHA): 1.2 grams of EPA and DHA or 3-4 grams of fish oil.

Dosage Forms

Alpha linolenic acid (omega-3): oil in gelatin capsules and in oil such as flaxseed oil; EPA and DHA: fish oils in gelatin capsules.

Adult RDI

None established

Adult ODA

1 tablespoon

RDA

  • General RDA: None Established

Interactions and Depletions

Interactions

Active Forms

Alpha-linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

Absorption

Digestion and absorption of fats, including omega-3 fatty acids, takes place in the small intestine.

Toxicities & Precautions

General

Omega-3 is a highly unsaturated fatty acid susceptible to oxidative damage in the body. Thus, people consuming omega-3 should take adequate amounts of antioxidant nutrients, especially vitamin E, vitamin C, and selenium. (2) , (3)

When omega-3 is purchased as a liquid, such as flaxseed oil, it needs to be refrigerated to prevent it from becoming rancid.

Care should be taken to minimize exposure of omega-3 fatty acids to heat, light, and oxygen.

If an omega-3 fatty acids becomes rancid, it develops a bitter taste and should be discarded.

Functions in the Body

Cellular Structure

Alpha linolenic acid is one of the primary structural components in cell walls and cellular membranes throughout the body. DHA is the most abundant long chain fatty acid in cells within the brain.

Blood Thinning

Aids in reducing platelet stickiness and acts as a mild blood thinner.

Regulation

Precursor for an important group of chemicals called the series 3 prostaglandins, which regulate things like inflammation, blood pressure, hormone production, and the activity of the immune and central nervous systems.

Development

Longer chain omega-3 fatty acids are important in the development of the brain and the retina of the eyes in early growth.

Skeletal health

It has been suggested that omega-3 fatty acids may modulate eicosanoid biosynthesis and influence gene expression in ways that influence bone modeling and bone cell differentiation. (4)

Clinical Applications

Cardiovascular Disease

Cardiovascular health may be supported by omega-3 fatty acids in lowering blood pressure, relaxing blood vessels and lowering cholesterol levels. (5) , (6) , (7) Researchers found that dietary intake of omega-3 lowered levels of inflammation and endothelial activation, which might explain in part the effect of these fatty acids in preventing cardiovascular disease. (8) A study performed in Italy reported that patients supplementing their diets with omega-3 fatty acids had a lower death rate from heart conditions than patients who did not supplement their diets. (9)

Elevated Triglycerides

Supplementation with 3 to 5 grams daily of omega-3 fatty acids can result in a 30% to 50% reduction in elevated serum triglycerides. (10)

Skin Conditions

Abnormalities in fatty acid metabolism found in people with problems such as psoriasis and eczema and therapy with omega-3 fatty acids is frequently beneficial.

Allergies

Individuals with allergic conditions have been found to have a defect in the enzyme responsible for synthesizing the longer chain omega-3 fatty acids. (11)

Elevated Cholesterol

Dietary alpha-linolenic acid reported to lower cholesterol levels in the blood and in liver tissues. (12)

Hypertension

Supplementation with the longer-chain omega-3 fatty acids provides a slight lowering of blood pressure. Reductions range between 3 and 10 mm Hg for both systolic and diastolic pressures. (13)

ADHD

Studies have found that subjects with ADHD had significantly lower concentrations of omega-3 fatty acids. (14)

Asthma

Supplementation with omega-3 may prevent and alleviate symptoms of asthma. (15) , (16)

Cancer

Dietary intake of omega-3 may play a role in the prevention and healing process of several types of cancers. (17) , (18) , (19) , (20) A study involving postoperative cancer patients were supplemented with omega-3 and experienced improved liver and pancreas function, which might have contributed to faster recovery of the patients. (21)

Depression

People with omega-3 deficiency in the United States as well as other countries may be vulnerable to depression. (22) , (23)

Rheumatoid Arthritis

Several studies indicate that omega-3 may reduce the symptoms of rheumatoid arthritis. (24) , (25)

Macular Degeneration

It has been reported that higher dietary intake of omega-3 fatty acids and fish relative levels of linoleic acid reduces the risk of developing age-related macular degeneration. (26)

Symptoms and Causes of Deficiency

Since omega-3 is the precursor for the series 3 prostaglandins, a deficiency of these fatty acids can result in a wide variety of problems related to organ, endocrine, and immune function. Deficiency is primarily due to a lack of dietary intake and the fact that omega-3 has been almost totally removed from most processed foods.

Dietary Sources

Flaxseed, chia, rapeseed, soybeans, alfalfa, and walnuts contain omega-3 fatty acids. Cold water fish and wild game also are sources of omega-3 fatty acids. In most cases, people are not able to consume adequate alpha-linolenic acid from dietary sources, and nutritional supplementation is recommended.

References

  1. Unsaturated Fatty Acids: Nutritional and Physiological Significance. The Report of the British Nutrition Foundation’s Task Force. London: Chapman and Hall; 1992.
  2. View Abstract: Holm T, et al. Omega-3 fatty acids enhance tumor necrosis factor-alpha levels in heart transplant recipients. Transplantation. Aug2001;72(4):706-11.
  3. View Abstract: Yam D, Peled A, Shinitzky M. Suppression of tumor growth and metastasis by dietary fish oil combined with vitamins E and C and cisplatin. Cancer Chemother Pharmacol. 2001;47(1):34-40.
  4. View Abstract: Watkins BA, Li Y, Lippman HE, et al. Omega-3 polyunsaturated fatty acids and skeletal health. Exp Biol Med (Maywood). Jun2001;226(6):485-97.
  5. View Abstract: Knapp HR, et al. The Antihypertensive Effects of Fish Oil. A Controlled Study of Polyunsaturated Fatty Acid Supplements in Essential Hypertension. N Engl J Med. Apr1989;320(16):1037-43.
  6. View Abstract: Harris WS, Park Y, Isley WL. Cardiovascular disease and long-chain omega-3 fatty acids. Curr Opin Lipidol. 2003 Feb;14(1):9-14.
  7. View Abstract: Laidlaw M, Holub B. Effects of supplementation with fish oil-derived n-3 fatty acids and gamma-linolenic acid on circulating plasma lipids and fatty acid profiles in women. Am J Clin Nutr. 2003 Jan;77(1):37-42.
  8. View Abstract: Lopez-Garcia E, Schulze MB, Manson JE, et al. Consumption of (n-3) fatty acids is related to plasma biomarkers of inflammation and endothelial activation in women. J Nutr. Jul2004;134(7):1806-11.
  9. View Abstract: O'Keefe JH, Harris WS. From Inuit to implementation: omega-3 fatty acids come of age. Mayo Clin Proc. Jun2000;75(6):607-14.
  10. View Abstract: O’Keefe JH, Harris WS. From Inuit to implementation: omega-3 fatty acids come of age. Mayo Clin Proc. Jun2000;75(6):607-14.
  11. View Abstract: Galland L. Increased Requirements for Essential Fatty Acids in Atopic Individuals: A Review with Clinical Descriptions. J Am Coll Nutr. 1986;5(2):213-28.
  12. View Abstract: Garg ML, et al. Alpha-linolenic Acid and Metabolism of Cholesterol and Long-chain Fatty Acids. Nutrition. Jun1992;8(3):208-10.
  13. View Abstract: Knapp HR, et al. The Antihypertensive Effects of Fish Oil. A Controlled Study of Polyunsaturated Fatty Acid Supplements in Essential Hypertension. N Engl J Med. Apr1989;320(16):1037-43.
  14. View Abstract: Stevens L, Zentall SS, Deck JL. Essential fatty acid metabolism in boys with attention-deficit hyperactivity disorder. Am J Clin Nutr. 1995;62:761-768.
  15. View Abstract: Masuev KA. The Effect of Polyunsaturated Fatty Acids of the Omega-3 Class on the Late Phase of the Allergic Reaction in Bronchial Asthma Patients. Ter Arkh. 1997;69(3):31-33.
  16. View Abstract: Oddy WH, de Klerk NH, Kendall GE, Mihrshahi S, Peat JK. Ratio of omega-6 to omega-3 fatty acids and childhood asthma. J Asthma. 2004;41(3):319-26.
  17. View Abstract: Bagga D, et al. Dietary Modulation of Omega-3/Omega-6 Polyunsaturated Fatty Acid Ratios in Patients with Breast Cancer. J Natl Cancer Inst. Aug1997;89(15):1123-31.
  18. View Abstract: Pandalai PK, et al. The Effects of Omega-3 and Omega-6 Fatty Acids on in Vitro Prostate Cancer Growth. Anticancer Res. Apr1996;16(2):815-20.
  19. View Abstract: Anti M, et al. Effect of Omega-3 Fatty Acids on Rectal Mucosal Cell Proliferation in Subjects at Risk for Colon Cancer. Gastroenterology. Sep1992;103(3):883-91.
  20. View Abstract: Leitzmann MF, Stampfer MJ, Michaud DS, et al. Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer. Am J Clin Nutr. Jul2004;80(1):204-16.
  21. View Abstract: Heller AR, Rossel T, Gottschlich B, et al. Omega-3 fatty acids improve liver and pancreas function in postoperative cancer patients. Int J Cancer. Sep2004;111(4):611-6.
  22. View Abstract: Hibbeln JR, et al. Dietary polyunsaturated fatty acids and depression: when cholesterol does not satisfy. Am j Clin Nutr. Jul1995;62(1):1-9.
  23. View Abstract: Tiemeier H, van Tuijl HR, Hofman A, Kiliaan AJ, Breteler MM. Plasma fatty acid composition and depression are associated in the elderly: the Rotterdam Study. Am J Clin Nutr. Jul2003;78(1):40-6.
  24. View Abstract: Geusens P, et al. Long-term Effect of Omega-3 Fatty Acid Supplementation in Active Rheumatoid Arthritis. A 12-month, Double-blind, Controlled Study. Arthritis Rheum. Jun1994;37(6):824-29.
  25. View Abstract: Cleland LG, Proudman SM, Hall C, et al. A biomarker of n-3 compliance in patients taking fish oil for rheumatoid arthritis. Lipids. Apr2003;38(4):419-24.
  26. View Abstract: Seddon JM, Rosner B, Sperduto RD, et al. Dietary fat and risk for advanced age-related macular degeneration. Arch Ophthalmol. Aug2001;119(8):1191-9.