Omega-3 fatty acids are polyunsaturated fatty acids found in certain fish tissues, and in vegetable sources such as flax seeds, walnuts, and canola oil.

Omega-3 fatty acids are classed as essential fatty acids. These fatty acids were originally designated as "Vitamin F", until it was realized that they must be classified with the fats.

The term "omega-3" signifies that the first double bond in the carbon backbone of the fatty acid, counting from the end opposite the acid group, occurs in the third carbon-carbon bond. This way of counting was introduced by physiologists. Chemists would normally count the position of the double bond from the acid end position (the alpha positions). However by counting from the other end, physiologists revealed the similarity between fatty acids of diverse length.

Like all polyunsaturated fatty acids, the omega-3 fatty acids have minimum 2 and maximum 6 double bonds in a carbon chain that ranges from 18 until 22 carbon atoms.

In natural conditions, the double bonds are in the cis-conformation, with the two hydrogen atoms at the same side of the double bond. This characteristic, along with the fact that every double bond is separated by a methyl group, explains the 3D-structure and the properties of omega-3 and omega-6 fatty acids as well as those of the phospholipids that contain them. With every additional cis bond, the carbon chain will change direction, so that the long omega-3 and omega-6 chain structure is not one long straight chain, but a twisted molecule. This simple difference explains a host of biological phenomena in structures that are rich in polyunsaturated fatty acids, especially the lipid bilayer of the cell membrane.

Contents

1 Biological importance of omega-3 (and omega-6) fatty acids 2 Benefits of omega-3 fatty acids 3 Known and suspected risks of omega-3 fatty acids 4 References 5 See also 6 External links

Biological importance of omega-3 (and omega-6) fatty acids

Common omega-3 fatty acids in the body are (alpha)linolenic acid (18:3), eicosapentaenoic acid (20:5), docosahexaenoic acid (22:6). Gamma-linolenic acid is an omega-6 fatty acid.

It has been conjectured that the diet in the Human Environment of Evolutionary Adaptedness may have been rich in seafood, nuts and other sources of vegetable omega-3, and that modern diets have an unhealthy ratio of omega-6 to omega-3 fatty acids. An optimal ratio for cadriovascular health is thought to be 4:1 or less, but the introduction of processed foods with very high ratios of omega-6 to omega-3 in the last fifty years is probably partially responsible for the fact that heart disease is the number one killer in the United States today.

Arachidonic acid, an omega-6 fatty acid (C20:4, n-6), is one of the most important precursors of anti-inflammatory prostaglandins. These precursors are jointly referred to as eicosanoids since they have 20 carbon atoms (eicosa is Greek for 20). Since the metabolism of omega-3 and omega-6 fatty acids shares common enzymes (elongase and desaturase enzymes), its is widely accepted that both types of polyunsaturated fatty acids behave as competitive substrates. However, the desaturation of omega-3 fatty acids leads to less inflammatory eicosanoids than arachidonic acid. It is also likely that omega-3 fatty acids such as eicosapentaenoic acid have very specific biological activities. EPA supplementation inhibits or attenuates the pro-inflammatory cascade that follows on the enzymatic release of free arachidonic acid from the cell membrane. In this respect, some researchers have uncovered interesting parallels between the biological effect of aspirin, NSAIDs (non-steroidal anti-inflammatory drugs) and fish oil.

The scientific and commercial attention given to the effect of omega-3 fats on inflammation and inflammatory signals has increased significantly since the 1990s.

Benefits of omega-3 fatty acids

There have been thousands of studies proving the benefits of Omega-3 fatty acids, here is just a sample:

• There are preliminary reports that supplementing the diet with large doses of omega-3 oils may act as a mood stabilizer, opening the possibility of their use as a treatment for depression and bipolar disorder. However, the reports relating to this state that care must be taken to avoid overdose.
• Lower doses have also been reported as having possible beneficial cardiovascular effects.
• There are also reports that omega-3 fatty acids may lower the risk of dementia in old age.
• General heart benefits: Heart disease is a widespread health problem in modern society. Fish oil, rich in omega-3 fatty acids (DHA and EPA) has been proven in many clinical studies to benefit heart health, also supported by the American Heart Association guidelines
• Lowers Triglycerides: The effectiveness of Fish oil in lowering blood triglycerides (fats) known to be a risk factor for cardiovascular disease has been well established in multiple clinical studies.
• Benefits Hypertension (High blood pressure): Fish oil has been shown to lower mild hypertension when it is due to cardiovascular disease, specifically high cholesterol and atherosclerosis (hardening of the artery walls).
• Anti-clotting: Fish oil helps avoid thrombosis (blood clots) as it prevents platelets (smallest cells in the blood) to stick together and form blood clots.
• Reduces Heart Irregularities: Fish oil... especially the DHA content of it has been shown to lower heart rates and also prevent arrhythmias (disturbances of the normal rhythm in the heart's beating), thus decreasing the chance of sudden death by a heart attack.
• Circulatory problems: Circulatory problems such as varicose veins and Raynaud's disease benefit from fish oil. Fish oil stimulates blood circulation and increases the breakdown of fibrin, a compound involved in clot and scar formation.
• Depression: Persons with mood disorders such as depression benefit from fish oil supplementation. Lack of omega-3 fatty acids and in particular DHA has been linked by researchers to depression.
• Aggression: A new study of teenagers has found that fish oil and DHA consumption relates to lower hostility rates in teenagers. Hostility has been shown to predict the development and manifestation of heart disease.
• Attention Deficit-Hyperactivity Disorder (ADHD), dyslexia and dyspraxia: Like depression and other mood disorders, persons who suffer from ADHD, dyslexia and dyspraxia (absence of ability to perform coordinated skilled movements or clumsiness) benefit from fish oil supplementation.
• Memory, learning and Alzheimer's Disease: Studies have proven that omega-3 fatty acids improve brain function and that intake of fish oil and DHA is linked to a lowered risk of developing Alzheimer's disease. Studies suggest that fish oil and DHA may protect the nervous system.
• Studies learn that omega-3 fatty acid-intake by mothers during pregnancy may protect babies against the development of allergies. Fish oil has been found to protect against symptoms of hay fever, sinus infections, asthma, food allergies and allergic skin conditions such as hives and eczema
• Skin disorders such as psoriasis have been shown to improve from fish oils. In the skin of persons with psoriasis the amount of compounds causing inflammation is many times greater than normal. Fish oil inhibits the production of these inflammatory compounds. Fish oil improves the health of skin, nails and hair.
• Fish oil supplements have been shown to benefit in rheumatoid arthritis (RA), and other inflammatory forms of arthritis, such as occurs in some persons with psoriasis and gout. EPA and DHA in fish oil reduce the amount of compounds causing inflammation.
• Diabetics suffering from non-insulin dependent diabetes or type II diabetes benefit from fish oil supplementation. Research show that persons who consume 5-10 percent of their dietary energy consumption in the form of fish or fish oil, have less insulin resistance.
• The intake of fish oil has been proven to be beneficial for the body's immune function. Research has linked intake of fish oil to a lowered risk of breast cancer and prostate cancer.
• The consumption of fish oil lowers the risk for cardiovascular disease and osteoporosis in post-menopausal women. (Pre)Menstrual symptoms such as menstrual pain are often alleviated from the use of fish oil supplementation. Omega-3 fatty acids are converted into pain relieving substances (prostaglandins type-3) that control contractions of the uterus, which cause the cramping.
• Research has shown that consumption of fish oil is linked to lowered risk of age related macular degeneration, an eye condition which is the leading cause of severe visual loss in people over age 50.
• Fish oil has been proven to be beneficial in intestinal health. Fish oil has an anti-inflammatory effect in inflammatory bowel disease (Ulcerative colitis and Crohn's disease).

Known and suspected risks of omega-3 fatty acids

In its letter entitled Letter Regarding Dietary Supplement Health Claim for Omega-3 Fatty Acids and Coronary Heart Disease the U. S. Food and Drug Administration Center for Food Safety and Applied Nutrition, Office of Nutritional Products, Labeling, and Dietary Supplements noted that the known or suspected risks of omega-3 fatty acids may include:

• increased bleeding times,
• the possibility of hemorrhagic stroke,
• oxidation of omega-3 fatty acids forming biologically active oxidation products,
• increased levels of low density lipoproteins (LDL) cholesterol or apoproteins associated with LDL cholesterol among diabetics and hyperlipidemics,
• reduced glycemic control among diabetics.
• suppression of immune and inflammation responses, and consequently, to decreased resistance to infections and increased susceptibility to opportunistic bacteria

In addition, another potential risk is the possibility of vitamin poisoning from taking large doses of supplements which contain significant amounts of vitamins in addition to omega-3 fatty acids.

For these reasons, the FDA recommends that total dietary intake of omega-3 fatty acids be limited to 3g/day, of which no more than 2g/day should come from nutritional supplements. [1] However, many nutritionists recommend more than this, pointing out that the studies used by the FDA only indirectly show that high doses of omega-3 fatty acids are harmful.

References

• Andrew L. Stoll et al. Omega 3 Fatty Acids in Bipolar Disorder - A Preliminary Double-blind, Placebo-Controlled Trial
• "FDA ANNOUNCES DECISION ON ANOTHER HEALTH CLAIM FOR DIETARY SUPPLEMENTS"
• U. S. Food and Drug Administration Center for Food Safety and Applied Nutrition, Office of Nutritional Products, Labeling, and Dietary Supplements: Letter Regarding Dietary Supplement Health Claim for Omega-3 Fatty Acids and Coronary Heart Disease (Docket No. 91N-0103)
• BBC News story: Fish 'lowers dementia risk'
• Salonen JT, Seppanen K, Nyyssonen K, et al. Intake of mercury from fish, lipid peroxidation, and the risk of myocardial infarction and coronary, cardiovascular, and any death in eastern Finnish men. Circulation 1995;91:645-55.
• Pheatt N, Ed. Nonherbal Dietary Supplements. Pharmacist's Letter Continuing Education Booklet 1998;98:1-51.
• Shils M, Olson A, Shike M. Modern Nutrition in Health and Disease. 8th ed. Philadelphia, PA: Lea and Febiger, 1994.
• Akedo I, Ishikawa H, Nakamura T, et al. Three cases with familial adenomatous polyposis diagnosed as having malignant lesions in the course of a long-term trial using docosahexanoic acid (DHA)-concentrated fish oil capsules. Jpn J Clin Oncol 1998;28:762-5.
• Danno K, Sugie N. Combination therapy with low-dose etretinate and eicosapentaenoic acid for psoriasis vulgaris. J Dermatol 1998;25:703-5.
• Prisco D, Paniccia R, Bandinelli B, et al. Effect of medium-term supplementation with a moderate dose of n-3 polyunsaturated fatty acids on blood pressure in mild hypertensive patients. Thromb Res 1998;1:105-12.
• Gans RO, Bilo HJ, Weersink EG, et al. Fish oil supplementation in patients with stable claudication. Am J Surg 1990;160:490-5.
• Vognild E, Elvevoll EO, Brox J, et al. Effects of dietary marine oils and olive oil on fatty acid composition, platelet membrane fluidity, platelet responses, and serum lipids in healthy humans. Lipids 1998;33:427-36.
• Mayser P, Mrowietz U, Arenberger P, et al. Omega-3 fatty acid-based lipid infusion in patients with chronic plaque psoriasis: results of a double-blind, randomized, placebo-controlled, multicenter trial. J Am Acad Dermatol 1998;38:539-47.
• Campan P, Planchand PO, Duran D. Pilot study on n-3 polyunsaturated fatty acids in the treatment of human experimental gingivitis. J Clin Periodontol 1997;24:907-13.
• Singh RB, Niaz MA, Sharma JP, et al. Randomized, double-blind, placebo-controlled trial of fish oil and mustard oil in patients with suspected acute myocardial infarction: the Indian experiment of infarct survival-4. Cardiovasc Drugs Ther 1997;11:485-91.
• Sagar PS, Das UN, Koratkar R, et al. Cytotoxic action of cis-unsaturated fatty acids on human cervical carcinoma (HeLa) cells: relationship to free radicals and lipid peroxidation and its modulation by calmodulin antagonists. Cancer Lett 1992;63:189-98.
• Grimsgaard S, Bonaa KH, Hansen JB, Nordoy A. Highly purified eicosapentaenoic acid and docosahexaenoic acid in humans have similar triacylglycerol-lowering effects but divergent effects on serum fatty acids. Am J Clin Nutr 1997;66:649-59.
• Allard JP, Kurian R, Aghdassi E, Muggli R, et al. Lipid peroxidation during n-3 fatty acid and vitamin E supplementation in humans. Lipids 1997;32:535-41.
• Andreassen AK, Hartmann A, Offstad J, et al. Hypertension prophylaxis with omega-3 fatty acids in heart transplant recipients. J Am Coll Cardiol 1997;29:1324-31.
• Badalamenti S, Salerno F, Salmeron JM, et al. Lack of renal effects of fish oil administration in patients with advanced cirrhosis and impaired glomerular filtration. Hepatol 1997;25:313-6.
• Agren JJ, Hanninen O, Julkunen A, et al. Fish diet, fish oil and docosahexaenoic acid rich oil lower fasting and postprandial plasma lipid levels. Eur J Clin Nutr 1996;50:765-71.
• van der Tempel H, Tulleken JE, Limburg PC, et al. Effects of fish oil supplementation in rheumatoid arthritis. Ann Rheum Dis 1990;49:76-80.
• Toft I, Bonaa KH, Ingebretsen OC, et al. Effects of n-3 polyunsaturated fatty acids on glucose homeostasis and blood pressure in essential hypertension. A randomized, controlled trial. Ann Intern Med 1995;123:911-8.
• Badalamenti S, Salerno F, Lorenzano E, et al. Renal effects of dietary supplementation with fish oil in cyclosporine- treated liver transplant recipients. Hepatol 1995;22:1695-71.
• Sacks FM, Stone PH, Gibson CM, et al. Controlled trial of fish oil for regression of human coronary atherosclerosis. HARP Res Group. J Am Coll Cardiol 1995;25:1492-8.
• Eritsland J, Arnesen H, Seljeflot I, Hostmark AT. Long-term metabolic effects of n-3 polyunsaturated fatty acids in patients with coronary artery disease. Am J Clin Nutr 1995;61:831-6.
• Shimizu H, Ohtani K, Tanaka Y, et al. Long-term effect of eicosapentaenoic acid ethyl (EPA-E) on albuminuria of non-insulin dependent diabetic patients. Diabetes Res Clin Pract 1995;28:35-40.
• Onwude JL, Lilford RJ, Hjartardottir H, et al. A randomised double blind placebo controlled trial of fish oil in high risk pregnancy. Br J Obstet Gynaecol 1995;102:95-100.
• Bulstra-Ramakers MT, Huisjes HJ, Visser GH. The effects of 3g eicosapentaenoic acid daily on recurrence of intrauterine growth retardation and pregnancy induced hypertension. Br J Obstet Gynaecol 1995;102:123-6.
• Leaf A, Jorgensen MB, Jacobs AK, et al. Do fish oils prevent restenosis after coronary angioplasty? Circulation 1994;90:2248-57.
• McVeigh GE, Brennan GM, Cohn JN, et al. Fish oil improves arterial compliance in non-insulin-dependent diabetes mellitus. Arterioscler Thromb 1994;14:1425-9.
• Sacks FM, Hebert P, Appel LJ, et al. Short report: the effect of fish oil on blood pressure and high-density lipoprotein-cholesterol levels in phase I of the trials of hypertension prevention. J Hypertens 1994;12:209-13.
• Lau CS, Morley KD, Belch JJ. Effects of fish oil supplementation on non-steroidal anti-inflammatory drug requirement in patients with mild rheumatoid arthritis- a double-blind, placebo-controlled study. Br J Rheumatol 1993;32:982-9.
• Rossi E, Costa M. Fish oil derivatives as a prophylaxis of recurrent miscarriage associated with antiphospholipid antibodies (APL): a pilot study. Lupus 1993;2:319-23.

See also

• Omega-6 fatty acid
• Grape seed oil
• Cod liver oil
• Fish oil
• Resolvins

External links

• New Findings About Omega-3 Fatty Acids and Depression
• The A-Z`s of Omega 3`s
• Fish Oil Blog News and commentary on the latest developments and benefits of fish oil and omega-3 fatty acids.
• BBC News report: Oily fish helps cut inflammation, March 12, 2005.