Omega-6 fatty acid: Difference between revisions
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{{For2|an explanation of ''n'' and numerical nomenclature (such as ''n''−6 or 18:2)|[[Fatty acid#Nomenclature|Nomenclature of fatty acids]]}} |
{{For2|an explanation of ''n'' and numerical nomenclature (such as ''n''−6 or 18:2)|[[Fatty acid#Nomenclature|Nomenclature of fatty acids]]}} |
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{{Fats}} |
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[[Image:LAnumbering.png|375px|thumb|The [[chemical structure]] of [[linoleic acid]], a common ''n''−6 fatty acid |
[[Image:LAnumbering.png|375px|thumb|The [[chemical structure]] of [[linoleic acid]], a common ''n''−6 fatty acid foundf in many [[vegetable oil]]s.]] |
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'''''n''−6 fatty acids''' (popularly referred to as '''ω−6 fatty acids''' or '''omega-6 fatty acids''') are a family of [[unsaturated fat|unsaturated]] [[fatty acid]]s which have in common a carbon–carbon [[double bond#Bond order|double bond]] in the [[Fatty acid#Nomenclature|''n''−6]] position; that is, the sixth bond from the end of the fatty acid. |
'''''n''−6 fatty acids''' (popularly referred to as '''ω−6 fatty acids''' or '''omega-6 fatty acids''') are a family of [[unsaturated fat|unsaturated]] [[fatty acid]]s which have in common a carbon–carbon [[double bond#Bond order|double bond]] in the [[Fatty acid#Nomenclature|''n''−6]] position; that is, the sixth bond from the end of the fatty acid. |
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| first = Joseph R. |
| first = Joseph R. |
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| coauthros = Nieminen, Levi R.G.; Blasbalg, Tanya L.; Riggs, Jessica A.; and Lands, William E.M. |
| coauthros = Nieminen, Levi R.G.; Blasbalg, Tanya L.; Riggs, Jessica A.; and Lands, William E.M. |
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| title = Healthy intakes of ''n''−3 and ''n''−6 fatty acids: estimations considering worldwide diversity |
| title = Healthy intakes of ''n''−3 and ''n''−6 fatty acids: estimations considering worldwide diversity |
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| journal = American Journal of Clinical Nutrition |
| journal = American Journal of Clinical Nutrition |
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| publisher = American Society for Nutrition |
| publisher = American Society for Nutrition |
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Revision as of 23:20, 2 July 2008
 | It has been suggested that this article be merged with fatty acid. (Discuss) Proposed since December 2007. |
| Types of fats in food |
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| Components |
| Manufactured fats |
n−6 fatty acids (popularly referred to as ω−6 fatty acids or omega-6 fatty acids) are a family of unsaturated fatty acids which have in common a carbon–carbon double bond in the n−6 position; that is, the sixth bond from the end of the fatty acid.
The biological effects of the n−6 fatty acids are largely mediated by their conversion to n-6 eicosanoids that bind to diverse receptors found in every tissue of the body. The conversion of tissue arachidonic acid (20:4n-6) to n-6 prostaglandin and n-6 leukotriene hormones provides many targets for pharmaceutical drug development and treatment to diminish excessive n-6 actions in atherosclerosis, asthma, arthritis, vascular disease, thrombosis, immune-inflammatory processes and tumor proliferation. Competitive interactions with the n−3 fatty acids affect the relative storage, mobilization, conversion and action of the n-3 and n-6 eicosanoid precursors. (See Essential fatty acid interactions for more information.)
Key n−6 fatty acids
Linoleic acid (18:2, n−6), the shortest-chained n−6 fatty acid, is an essential fatty acid. Arachidonic acid (20:4) is a physiologically significant n−6 fatty acid and is the precursor for prostaglandins and other physiologically active molecules.
Negative health effects
Some medical research suggests that excessive levels of n−6 fatty acids, relative to n−3 fatty acids, may increase the probability of a number of diseases and depression.[1][2][3]
Modern Western diets typically have ratios of n−6 to n−3 in excess of 10 to 1, some as high as 30 to 1. The optimal ratio is thought to be 4 to 1 or lower.[4][5]
Excess n−6 fats interfere with the health benefits of n−3 fats; in part because they compete for the same rate-limiting enzymes. A high proportion of n−6 to n−3 fat in the diet shifts the physiological state in the tissues toward the pathogenesis of many diseases: prothrombotic, proinflammatory and proconstrictive.[6]
Chronic excessive production of n−6 eicosanoids is associated with heart attacks, thrombotic stroke, arrhythmia, arthritis, osteoporosis, inflammation, mood disorders and cancer.[7] Many of the medications used to treat and manage these conditions work by blocking the effects of the potent n−6 fat, arachidonic acid.[8] Many steps in formation and action of n-6 hormones from n-6 arachidonic acid proceed more vigorously than the corresponding competitive steps in formation and action of n-3 hormones from n-3 eicosapentaenoic acid. [9] The COX-1 and COX-2 inhibitor medications, used to treat inflammation and pain, work by preventing the COX enzymes from turning arachidonic acid into inflammatory compounds.[10] (See Cyclooxygenase for more information.) The LOX inhibitor medications often used to treat asthma, work by preventing the LOX enzyme from converting arachidonic acid into the leukotrienes.[11][12] Many of the anti-mania medications used to treat bipolar disorder work by targeting the arachidonic acid cascade in the brain.[13]
Dietary Linoleic Acid Requirement
Adding more controversy to the n−6 fat issue is that the dietary requirement for linoleic acid (the key n−6 fatty acid), has been seriously questioned, because of a significant methodology error discovered by University of Toronto scientist, Stephen Cunnane.[14] Cunnane discovered that the seminal research used to determine the dietary requirement for linoleic acid was based on feeding animals linoleic acid-deficient diets, which were simultaneously deficient in n−3 fats. The n−3 deficiency was not taken into account. The n−6 oils added back systematically to correct the deficiency also contained trace amounts of n−3 fats. Therefore the researchers were inadvertently correcting the n−3 deficiency as well. Ultimately, it took more oil to correct both deficiencies. According to Cunnane, this error overestimates LA requirements by 5 to 15 times.
Dietary sources
Four major food oils (palm, soybean, rapeseed and sunflower) provide more than 100 million metric tons annually, providing more than 32 million metric tons of n-6 linoleic acid and 4 million metric tons of n-3 alpha-linolenic acid Cite error: The <ref> tag has too many names (see the help page).
- poultry
- eggs
- cereals
- whole-grain breads
- baked goods
- nuts
- most vegetable oils
- evening primrose oil
- borage oil
- blackcurrant seed oil
- linseed oil
- soybean oil
- cottonseed oil
- sunflower seed oil
- corn oil
- safflower oil
- pumpkin seeds
List of n−6 fatty acids
| Common name | Lipid name | Chemical name |
|---|---|---|
| Linoleic acid | 18:2 (n−6) | 9,12-octadecadienoic acid |
| Gamma-linolenic acid | 18:3 (n−6) | 6,9,12-octadecatrienoic acid |
| Eicosadienoic acid | 20:2 (n−6) | 11,14-eicosadienoic acid |
| Dihomo-gamma-linolenic acid | 20:3 (n−6) | 8,11,14-eicosatrienoic acid |
| Arachidonic acid | 20:4 (n−6) | 5,8,11,14-eicosatetraenoic acid |
| Docosadienoic acid | 22:2 (n−6) | 13,16-docosadienoic acid |
| Adrenic acid | 22:4 (n−6) | 7,10,13,16-docosatetraenoic acid |
| Docosapentaenoic acid | 22:5 (n−6) | 4,7,10,13,16-docosapentaenoic acid |
| Calendic acid | 18:3 (n−6) | 8E,10E,12Z-octadecatrienoic acid |
See also
References
- ^ Lands, William E.M. (2005). "Dietary fat and health: the evidence and the politics of prevention: careful use of dietary fats can improve life and prevent disease". Annals of the New York Academy of Sciences. 1055. Blackwell: 179–192. doi:10.1196/annals.1323.028. PMID 16387724.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Hibbeln, Joseph R. (2006). "Healthy intakes of n−3 and n−6 fatty acids: estimations considering worldwide diversity". American Journal of Clinical Nutrition. 83 (6, supplement). American Society for Nutrition: 1483S–1493S. PMID 16841858.
{{cite journal}}: Unknown parameter|coauthros=ignored (help); Unknown parameter|month=ignored (help) - ^ Okuyama, Hirohmi (2007). "ω3 fatty acids effectively prevent coronary heart disease and other late-onset diseases: the excessive linoleic acid syndrome". World Review of Nutritional Dietetics. 96 (Prevention of Coronary Heart Disease). Karger: 83–103. doi:10.1159/000097809. PMID 17167282. ISBN 3805581793.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Daley, C.A. (2004). "A literature review of the value-added nutrients found in grass-fed beef products". California State University, Chico (College of Agriculture). Retrieved 2008-03-23.
{{cite journal}}: Cite journal requires|journal=(help); Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Simopoulos, Artemis P. (2002). "The importance of the ratio of omega-6/omega-3 essential fatty acids". Biomedicine & Pharmacotherapy. 56 (8): 365–379. PMID 12442909.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Simopoulos, Artemis P. (2003). "Importance of the ratio of omega-6/omega-3 essential fatty acids: evolutionary aspects". World Review of Nutrition and Dietetics. 92 (Omega-6/Omega-3 Essential Fatty Acid Ratio: The Scientific Evidence). Karger: 1–174. doi:10.1159/000073788. PMID 14579680. ISBN 3805576404.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Calder, Philip C. (2006). "n−3 polyunsaturated fatty acids, inflammation, and inflammatory diseases". American Journal of Clinical Nutrition. 83 (6, supplement). American Society for Nutrition: 1505S–1519S. PMID 16841861.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Smith, William L. (2008). "Nutritionally essential fatty acids and biologically indispensable cyclooxygenases". Trends in Biochemical Sciences. 33 (1). Elsevier: 27–37. doi:10.1016/j.tibs.2007.09.013. PMID 18155912.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Wada, M. (2007). "Enzymes and receptors of prostaglandin pathways with arachidonic acid-derived versus eicosapentaenoic acid-derived substrates and products. Nutritionally essential fatty acids and biologically indispensable cyclooxygenases". J. Biol. Chem. 282 (31). ASBMB: 22254–22266.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Cleland, Leslie G. (2006). "Fish oil: what the prescriber needs to know". Arthritis Research & Therapy. 8 (1). BioMed Central: 202. doi:10.1186/ar1876. PMID 16542466.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help); Unknown parameter|month=ignored (help)CS1 maint: unflagged free DOI (link) - ^ Mickleborough, Timothy D. (2005). "Dietary omega-3 polyunsaturated fatty acid supplementation and airway hyperresponsiveness in asthma". The Journal of Asthma. 42 (5). Informa Healthcare: 305–314. doi:10.1081/JAS-200062950. PMID 16036405.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Broughton, K. Shane (2005). "Reduced asthma symptoms with n−3 fatty acid ingestion are related to 5-series leukotriene production". American Journal of Clinical Nutrition. 65 (4). American Society for Nutrition: 1011–1017. PMID 9094887.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help); Unknown parameter|month=ignored (help) - ^ Lee, H.J. (2007). "Antimanic therapies target brain arachidonic acid signaling: lessons learned about the regulation of brain fatty acid metabolism". Prostaglandins, Leukotrienes and Essential Fatty Acids. 77 (5). Elsevier: 239–246. doi:10.1016/j.plefa.2007.10.018. PMID 18042366.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help); Unknown parameter|month=ignored (help) - ^ Cunnane, Stephen C. (2003). "Problems with essential fatty acids: time for a new paradigm?". Progress in Lipid Research. 42 (6): 544–568. doi:10.1016/S0163-7827(03)00038-9. PMID 14559071.
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Additional sources
- Tokar, Steve (2005-09-02). "Omega-6 fatty acids cause prostate tumor cell growth in culture". Medical News Today. MediLexicon International. Retrieved 2008-03-23.
{{cite news}}: Check date values in:|date=(help) - "Brain fatty acid levels linked to depression". News-Medical.Net. AZoNetwork. 2005-05-25. Retrieved 2008-03-23.
{{cite news}}: Check date values in:|date=(help) - Tribole, E.F. (2006-03-27). "Excess Omega-6 Fats Thwart Health Benefits from Omega-3 Fats". British Medical Journal Rapid Responses to Hooper, et. al., 2006. Retrieved 2008-03-23.
{{cite journal}}: Check date values in:|date=(help); Italic or bold markup not allowed in:|journal=(help)