Omega-6 fatty acid
Types of fats in food |
---|
|
See also |
n−6 fatty acids (popularly referred to as ω−6 fatty acids or omega-6 fatty acids) are a family of unsaturated fatty acids that have in common a final carbon–carbon double bond in the n−6 position, that is, the sixth bond, counting from the end opposite the carboxyl group[citation needed].
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.)
Contents
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 (Omega-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, obesity, 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]
A high consumption of omega-6 polyunsaturated fatty acids (PUFAs), which are found in most types of vegetable oil, may increase the likelihood that postmenopausal women will develop breast cancer[14]. Similar effect was observed on prostate cancer[15]. Other "analysis suggested an inverse association between total polyunsaturated fatty acids and breast cancer risk, but individual polyunsaturated fatty acids behaved differently [from each other]. [...] a 20:2 derivative of linoleic acid [...] was inversely associated with the risk of breast cancer"[16].
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.[17] 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.[18]
Dietary sources of n−6 fatty acids include:[19][dead link][clarification needed]
- poultry
- eggs
- avocado
- nuts
- baked goods
- cereals
- whole-grain breads
- most vegetable oils
- evening primrose oil
- borage oil
- blackcurrant seed oil
- flax/linseed oil
- rapeseed or canola oil
- hemp oil
- soybean oil
- cottonseed oil
- sunflower seed oil
- corn oil
- safflower oil
- pumpkin seeds
- acai berry
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
- Essential fatty acid interactions
- Essential nutrients
- Linolenic acid
- n−3 fatty acid
- n−9 fatty acid
- Wheat germ oil
Notes & references
Cite error: Invalid <references>
tag;
parameter "group" is allowed only.
<references />
, or <references group="..." />
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.
- "Brain fatty acid levels linked to depression". News-Medical.Net. AZoNetwork. 2005-05-25. Retrieved 2008-03-23.
- 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.
External links
- Fats That Heal, Fats That Kill. Udo Erasmus 3rd ed. Burnaby (BC): Alive Books; 1993.
da:Omega-6-fedtsyre de:Omega-n-Fettsäuren#Omega-6-Fettsäuren es:Ácidos grasos omega 6 fr:Oméga-6 hi:ओमेगा-६ वसीय अम्ल it:Omega 6 nl:Omega-6-vetzuren ja:Ω-6脂肪酸 pl:Kwasy tłuszczowe omega-6 pt:Ômega 6 sv:Omega 6-fettsyra ta:ஒமேகா-6 கொழுப்பு அமிலம் tr:Omega-6 yağ asitleri
zh:Ω-6脂肪酸- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Calder, Philip C. (June 1, 2006). "n−3 polyunsaturated fatty acids, inflammation, and inflammatory diseases". American Journal of Clinical Nutrition. American Society for Nutrition. 83 (6, supplement): 1505S–1519S. PMID 16841861.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Emily Sonestedt, Ulrika Ericson, Bo Gullberg, Kerstin Skog, Håkan Olsson, Elisabet Wirfält (2008). "Do both heterocyclic amines and omega-6 polyunsaturated fatty acids contribute to the incidence of breast cancer in postmenopausal women of the Malmö diet and cancer cohort?". The International Journal of Cancer. UICC International Union Against Cancer. 123 (7): 1637–1643. doi:10.1002/ijc.23394. PMID 10970215. Retrieved 2008-11-30.
- ↑ Yong Q. Chen, at al (2007). "Modulation of prostate cancer genetic risk by omega-3 and omega-6 fatty acids". The Journal of Clinical Investigation. 117 (7): 1866–1875. doi:10.1172/JCI31494. PMC 1890998 Freely accessible. PMID 17607361. Retrieved 2008-11-30.
- ↑ Valeria Pala, Vittorio Krogh, Paola Muti, Véronique Chajès, Elio Riboli, Andrea Micheli, Mitra Saadatian, Sabina Sieri, Franco Berrino (July 18, 2001). "Erythrocyte Membrane Fatty Acids and Subsequent Breast Cancer: a Prospective Italian Study". JNCL. 93 (14): 1088. doi:10.1093/jnci/93.14.1088. PMID 11459870. Retrieved 2008-11-30.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Gunstone, Frank (December 2007) "Oilseed markets: Market update: Palm oil". INFORM (AOCS) 18(12): 835-836.
- ↑ "Omega-6 fatty acids". WholeHealthMD. Retrieved 2008-03-23.
- Pages with broken file links
- All articles with unsourced statements
- Articles with unsourced statements from May 2010
- Articles with invalid date parameter in template
- All articles with dead external links
- Articles with dead external links from August 2010
- Wikipedia articles needing clarification from May 2010
- Fatty acids
- Essential nutrients
- Treatment of bipolar disorder
- 2Fix
- Pages with script errors
- CS1 maint: Multiple names: authors list