Omega-6 fatty acid

The evening primrose flower (O. biennis) produces an oil containing a high content of γ-linolenic acid, a type of omega-6 fatty acid.

Omega-6 fatty acids (also referred to as ω-6 fatty acids or n-6 fatty acids) are a family of polyunsaturated 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 methyl end.[1]

Health effects

In the absence of high-quality evidence, the association between omega-6 fatty acids and certain health benefits is inconclusive.

A 2018 review found that an increased intake of omega‐6 fatty acids has been shown to reduce total serum cholesterol and may reduce myocardial infarction (heart attack), but found no significant change in LDL cholesterol and triglycerides.[2] A 2021 review found that omega-6 supplements do not affect the risk of CVD morbidity and mortality.[3] In contrast, the oxidized linoleic acid hypothesis states that the growing amount of linoleic acid (LA) accumulation in adipose tissue, specifically low density lipoproteins (LDL), actually induces atherosclerosis and coronary heart disease,[4] and a study done in 2015 found that LA in adipose tissue increased 136% between 1959 and 2008.[5]

Overconsumption of omega-6 fatty acids has been linked to several adverse health effects. A 2011 source outlining the differences of how omega-6 and omega-3 are processed in the body states that the ratio should not exceed 10:1,[6] and another source addresses the link between a high ratio and infertility in men.[7] A study involving Drosophila shows an increase in lipid mediators for the pathway of inflammatory responses with omega-6, and unaltered changes with omega-3.[8] Although Drosophila lack prostaglandins, in humans, omega-6 activates an increase in prostaglandin production, and other key mediators of inflammation. A study in 2003 showed that replacing omega-6 with omega-3 within cell membranes can protect the cell against inflammation.[9]

Dietary sources

Dietary sources of omega-6 fatty acids include:[10]

  • poultry
  • eggs
  • nuts
  • hulled sesame seeds
  • cereals
  • durum wheat
  • whole-grain breads
  • pumpkin seeds
  • hemp seeds

Vegetable oils

Vegetable oils are a major source of omega-6 linoleic acid. Worldwide, more than 100 million metric tons of vegetable oils are extracted annually from palm fruits, soybean seeds, rape seeds, and sunflower seeds, providing more than 32 million metric tons of omega-6 linoleic acid and 4 million metric tons of omega-3 alpha-linolenic acid.[11][12]

Properties of vegetable oils[13][14]
The nutritional values are expressed as percent (%) by mass of total fat.
TypeProcessing
treatment[15]		Saturated
fatty acids		Monounsaturated
fatty acids		Polyunsaturated
fatty acids		Smoke point
Total[13]Oleic
acid
(ω-9)		Total[13]α-Linolenic
acid
(ω-3)		Linoleic
acid
(ω-6)		ω-6:3
ratio
Avocado[16]11.670.652–66
[17]		13.5112.512.5:1250 °C (482 °F)[18]
Brazil nut[19]24.832.731.342.00.141.9419:1208 °C (406 °F)[20]
Canola[21]7.463.361.828.19.118.62:1204 °C (400 °F)[22]
Coconut[23]82.56.361.7175 °C (347 °F)[20]
Corn[24]12.927.627.354.715858:1232 °C (450 °F)[22]
Cottonseed[25]25.917.81951.915454:1216 °C (420 °F)[22]
Cottonseed[26]hydrogenated93.61.50.60.20.31.5:1
Flaxseed/linseed[27]9.018.41867.853130.2:1107 °C (225 °F)
Grape seed 10.414.814.3  74.90.1574.7very high216 °C (421 °F)[28]
Hemp seed[29]7.09.09.082.022.054.02.5:1166 °C (330 °F)[30]
High-oleic safflower oil[31]7.575.275.212.8012.8very high212 °C (414 °F)[20]
Olive, Extra Virgin[32]13.873.071.310.50.79.814:1193 °C (380 °F)[20]
Palm[33]49.337.0409.30.29.145.5:1235 °C (455 °F)
Palm[34]hydrogenated88.25.70
Peanut[35]16.257.155.419.90.31819.661.6:1232 °C (450 °F)[22]
Rice bran oil2538.438.436.62.234.4[36]15.6:1232 °C (450 °F)[37]
Sesame[38]14.239.739.341.70.341.3138:1
Soybean[39]15.622.822.657.77517.3:1238 °C (460 °F)[22]
Soybean[40]partially hydrogenated14.943.042.537.62.634.913.4:1
Sunflower[41]8.9963.462.920.70.1620.5128:1227 °C (440 °F)[22]
Walnut oil[42]unrefined9.122.822.263.310.452.95:1160 °C (320 °F)[43]

List of omega-6 fatty acids

The chemical structure of linoleic acid, a common omega-6 fatty acid found in many nuts, seeds, and vegetable oils.
Common name Lipid name Chemical name
Linoleic acid (LA) 18:2 (n−6) all-cis-9,12-octadecadienoic acid
Gamma-linolenic acid (GLA) 18:3 (n−6) all-cis-6,9,12-octadecatrienoic acid
Calendic acid 18:3 (n−6) 8E,10E,12Z-octadecatrienoic acid
Eicosadienoic acid 20:2 (n−6) all-cis-11,14-eicosadienoic acid
Dihomo-gamma-linolenic acid (DGLA) 20:3 (n−6) all-cis-8,11,14-eicosatrienoic acid
Arachidonic acid (AA, ARA) 20:4 (n−6) all-cis-5,8,11,14-eicosatetraenoic acid
Docosadienoic acid 22:2 (n−6) all-cis-13,16-docosadienoic acid
Adrenic acid 22:4 (n−6) all-cis-7,10,13,16-docosatetraenoic acid
Osbond acid 22:5 (n−6) all-cis-4,7,10,13,16-docosapentaenoic acid
Tetracosatetraenoic acid 24:4 (n−6) all-cis-9,12,15,18-tetracosatetraenoic acid
Tetracosapentaenoic acid 24:5 (n−6) all-cis-6,9,12,15,18-tetracosapentaenoic acid

The melting point of the fatty acids increases as the number of carbons in the chain increases.[44]

See also

References

  1. ↑ Chow, Ching Kuang (2001). Fatty Acids in Foods and Their Health Implications. New York: Routledge Publishing. OCLC 25508943.
  2. ↑ Hooper L, Al-Khudairy L, Abdelhamid AS, Rees K, Brainard JS, Brown TJ, Ajabnoor SM, O'Brien AT, Winstanley LE, Donaldson DH, Song F, Deane KH (2018). "Omega‐6 fats for the primary and secondary prevention of cardiovascular disease". Cochrane Database of Systematic Reviews. 11. CD011094. doi:10.1002/14651858.CD011094.pub4. PMC 6516799. PMID 30488422.
  3. ↑ Mazidi M, Shekoohi N, Katsiki N, Banach M (2021). "Omega-6 fatty acids and the risk of cardiovascular disease: insights from a systematic review and meta-analysis of randomized controlled trials and a Mendelian randomization study". Archives of Medical Science. 18 (2): 466–479. doi:10.5114/aoms/136070. PMC 8924827. PMID 35316920.
  4. ↑ DiNicolantonio, James J; O’Keefe, James H (2018-09-26). "Omega-6 vegetable oils as a driver of coronary heart disease: the oxidized linoleic acid hypothesis". Open Heart. 5 (2): e000898. doi:10.1136/openhrt-2018-000898. ISSN 2053-3624. PMC 6196963.
  5. ↑ Guyenet, Stephan J.; Carlson, Susan E. (November 2015). "Increase in Adipose Tissue Linoleic Acid of US Adults in the Last Half Century". Advances in Nutrition. 6 (6): 660–664. doi:10.3945/an.115.009944. ISSN 2161-8313. PMC 4642429.
  6. ↑ Viviana, Gómez Candela, Carmen Bermejo López, Laura Mª Loria Kohen (2011). Importance of a balanced omega 6/omega 3 ratio for the maintenance of health. Nutritional recommendations. Aula Médica Ediciones. OCLC 756243443.{{cite book}}: CS1 maint: multiple names: authors list (link)
  7. ↑ Reza Safarinejad, Mohammad; Safarinejad, Shiva (2012-06-04). "The roles of omega-3 and omega-6 fatty acids in idiopathic male infertility". Asian Journal of Andrology. 14 (4): 514–515. doi:10.1038/aja.2012.46. ISSN 1008-682X. PMC 3720081.
  8. ↑ Kwon, So Yeon; Massey, Karen; Watson, Mark A; Hussain, Tayab; Volpe, Giacomo; Buckley, Christopher D; Nicolaou, Anna; Badenhorst, Paul (2020-01-28). "Oxidised metabolites of the omega-6 fatty acid linoleic acid activate dFOXO". Life Science Alliance. 3 (2): e201900356. doi:10.26508/lsa.201900356. ISSN 2575-1077. PMC 6988086.
  9. ↑ Bagga, Dilprit; Wang, Ling; Farias-Eisner, Robin; Glaspy, John A.; Reddy, Srinivasa T. (2003-02-10). "Differential effects of prostaglandin derived from ω-6 and ω-3 polyunsaturated fatty acids on COX-2 expression and IL-6 secretion". Proceedings of the National Academy of Sciences. 100 (4): 1751–1756. doi:10.1073/pnas.0334211100. ISSN 0027-8424. PMC 149905.
  10. ↑ "Food sources of total omega 6 fatty acids". Archived from the original on 2011-10-07. Retrieved 2011-09-04.
  11. ↑ Gunstone, Frank (December 2007). "Market update: Palm oil". International News on Fats, Oils and Related Materials. 18 (12): 835–36. Archived from the original on 2013-04-03.
  12. ↑ "Soybean Oil Prices Suddenly Diverge from Energy Market" (PDF). Oilseeds: World Market and Trade. USDA (January 2009). 2009-01-12. FOP 1-09. Archived from the original (PDF) on 2013-03-09. Retrieved 2019-08-09., Table 03: Major Vegetable Oils: World Supply and Distribution at Oilseeds: World Markets and Trade Monthly Circular Archived 2010-10-18 at the Wayback Machine
  13. 1 2 3 "US National Nutrient Database, Release 28". United States Department of Agriculture. May 2016. All values in this table are from this database unless otherwise cited or when italicized as the simple arithmetic sum of other component columns.
  14. ↑ "Fats and fatty acids contents per 100 g (click for "more details"). Example: Avocado oil (user can search for other oils)". Nutritiondata.com, Conde Nast for the USDA National Nutrient Database, Standard Release 21. 2014. Retrieved 7 September 2017. Values from Nutritiondata.com (SR 21) may need to be reconciled with most recent release from the USDA SR 28 as of Sept 2017.
  15. ↑ "USDA Specifications for Vegetable Oil Margarine Effective August 28, 1996" (PDF).
  16. ↑ "Avocado oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  17. ↑ Ozdemir F, Topuz A (2004). "Changes in dry matter, oil content and fatty acids composition of avocado during harvesting time and post-harvesting ripening period" (PDF). Food Chemistry. Elsevier. pp. 79–83. Archived from the original (PDF) on 2020-01-16. Retrieved 15 January 2020.
  18. ↑ Wong M, Requejo-Jackman C, Woolf A (April 2010). "What is unrefined, extra virgin cold-pressed avocado oil?". Aocs.org. The American Oil Chemists' Society. Retrieved 26 December 2019.
  19. ↑ "Brazil nut oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  20. 1 2 3 4 Katragadda HR, Fullana A, Sidhu S, Carbonell-Barrachina ÁA (2010). "Emissions of volatile aldehydes from heated cooking oils". Food Chemistry. 120: 59–65. doi:10.1016/j.foodchem.2009.09.070.
  21. ↑ "Canola oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  22. 1 2 3 4 5 6 Wolke RL (May 16, 2007). "Where There's Smoke, There's a Fryer". The Washington Post. Retrieved March 5, 2011.
  23. ↑ "Coconut oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  24. ↑ "Corn oil, industrial and retail, all purpose salad or cooking, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  25. ↑ "Cottonseed oil, salad or cooking, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  26. ↑ "Cottonseed oil, industrial, fully hydrogenated, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  27. ↑ "Linseed/Flaxseed oil, cold pressed, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  28. ↑ Garavaglia J, Markoski MM, Oliveira A, Marcadenti A (2016). "Grape Seed Oil Compounds: Biological and Chemical Actions for Health". Nutrition and Metabolic Insights. 9: 59–64. doi:10.4137/NMI.S32910. PMC 4988453. PMID 27559299.
  29. ↑ Callaway J, Schwab U, Harvima I, Halonen P, Mykkänen O, Hyvönen P, Järvinen T (April 2005). "Efficacy of dietary hempseed oil in patients with atopic dermatitis". The Journal of Dermatological Treatment. 16 (2): 87–94. doi:10.1080/09546630510035832. PMID 16019622. S2CID 18445488.
  30. ↑ Melina V. "Smoke points of oils" (PDF). veghealth.com. The Vegetarian Health Institute.
  31. ↑ "Safflower oil, salad or cooking, high oleic, primary commerce, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  32. ↑ "Olive oil, salad or cooking, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  33. ↑ "Palm oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  34. ↑ "Palm oil, industrial, fully hydrogenated, filling fat, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  35. ↑ "Oil, peanut". FoodData Central. usda.gov.
  36. ↑ Orthoefer FT (2005). "Chapter 10: Rice Bran Oil". In Shahidi F (ed.). Bailey's Industrial Oil and Fat Products. Vol. 2 (6th ed.). John Wiley & Sons, Inc. p. 465. doi:10.1002/047167849X. ISBN 978-0-471-38552-3.
  37. ↑ "Rice bran oil". RITO Partnership. Retrieved 22 January 2021.
  38. ↑ "Oil, sesame, salad or cooking". FoodData Central. fdc.nal.usda.gov. 1 April 2019.
  39. ↑ "Soybean oil, salad or cooking, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  40. ↑ "Soybean oil, salad or cooking, (partially hydrogenated), fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
  41. ↑ "FoodData Central". fdc.nal.usda.gov.
  42. ↑ "Walnut oil, fat composition, 100 g". US National Nutrient Database, United States Department of Agriculture.
  43. ↑ "Smoke Point of Oils". Baseline of Health. Jonbarron.org.
  44. ↑ "Biochemical Properties of Lipids". The Medical Biochemistry Page. 2020-04-30. Retrieved 2022-05-11.

Bibliography

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