Polyunsaturated fat: Wikis

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Types of fats in food
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In nutrition, polyunsaturated fat, or polyunsaturated fatty acid, are fatty acids in which more than one double bond exists within the representative molecule. That is, the molecule has two or more points on its structure capable of supporting hydrogen atoms not currently part of the structure. Polyunsaturated fatty acids can assume a cis or trans conformation depending on the geometry of the double bond.

The lack of the extra hydrogen atoms on the molecule's surface typically reduces the strength of the compound's intermolecular forces, thus causing the melting point of the compound to be significantly lower. This property can be observed by comparing predominately unsaturated vegetable oils, which remain liquid even at relatively low temperatures, to much more saturated fats such as butter or lard which are mainly solid at room temperature. Trans fats are more similar to saturated fat than are cis fats in many respects, including the fact that they solidify at a higher temperature than cis fats.

Chemical structure of the polyunsaturated fat linoleic acid.
3D representation of linoleic acid in a bent conformation.

A fatty acid has a carboxylic acid at one end and a methyl group at the other end. Carbon atoms in a fatty acid are identified by Greek letters on the basis of their distance from the carboxylic acid. The carbon atom closest to the carboxylic acid is the alpha carbon, the next adjacent carbon is the beta carbon, etc. In a long-chain fatty acid the carbon atom in the methyl group is called the omega carbon because omega is the last letter of the Greek alphabet.

Omega-3 fatty acids have a double bond three carbons away from the methyl carbon, whereas omega-6 fatty acids have a double bond six carbons away from the methyl carbon. The illustration below shows the omega-6 fatty acid, linoleic acid.

Contents

Health

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Benefits

Polyunsaturated fat can be found mostly in nuts, seeds, fish, algae, leafy greens, and krill. Whole food sources are always best, as processing and heating damage polyunsaturated fats and renders them harmful to health (for example, by creating trans-fats and free radicals). Omega-3 fatty acids in fish oil, fish and seafood have been shown to lower the risk of heart attacks.[1] Omega-6 fatty acids in sunflower oil and safflower oil may also reduce the risk of cardiovascular disease.[2] Consumption of refined sugar and refined grain products also cause the body to metabolize omega-6 fats into pro-inflammatory prostaglandins.[citation needed]

Omega-3 fatty acids reduced prostate tumor growth, slowed histopathological progression, and increased survival[3]. Among n-3 fatty acids [Omega-3], neither long-chain nor short-chain forms were consistently associated with breast cancer risk. High levels of docosahexaenoic acid, however, the most abundant n-3 PUFA [Omega-3] in erythrocyte membranes, were associated with a reduced risk of breast cancer.[4].

Dietary intake of polyunsaturated fatty acids has been shown in several studies to decrease the risk of developing amyotrophic lateral sclerosis (ALS, a.k.a. Lou Gehrig's Disease)[5][6].

Relation to cancer

At least one study in mice has shown that consuming high amounts of polyunsaturated fat (but not monounsaturated fat) may increase the risk of metastasis in cancer patients. [1]. The researchers found that linoleic acid in polyunsaturated fats produced increasing membrane phase separation, and thereby increased adherence of circulating tumor cells to blood vessel walls and remote organs. According to the report 'The new findings support earlier evidence from other research that consuming high amounts of polyunsaturated fat may increase the risk of cancer spreading'. The propensity for polyunsaturated fats to oxidize is another possible risk factor,[1] [2] [7] [8]. This leads to the generation of free radicals and eventually to rancidity. Studies have shown that low dosages of Coenzyme Q10 reduce this oxidation, and a combination of a diet rich in polyunsaturated fatty acids and Coenzyme Q10 supplementation leads to a longer lifespan in rats[9]. Studies on animals have shown a link between polyunsaturated fat and the incidence of tumours. In some of these studies the incidence of tumours increased with increasing intake of polyunsaturated fat, up to about 5% of total energy, near to the middle of the current dietary intake in humans. However, studies in humans have found little evidence of an association between polyunsaturated fat and the risk of cancer.[citation needed] It is advised that the level of polyunsaturated fats in the diet be regulated if Coenzyme Q10 supplements are not being taken. However, even without Coenzyme Q10 supplementation, the effect on health might be more beneficial than harmful in terms of its effect on reducing cholesterol levels.

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[10]. Similar effect was observed on prostate cancer[11]. Other analysis suggested an inverse association between total polyunsaturated fatty acids and breast cancer risk, but individual polyunsaturated fatty acids behaved differently[4] from each other.

Some Examples of Foods containing polyunsaturated fat

See also

References

  1. ^ National Institute of Health (August 1, 2005). "Omega-3 fatty acids, fish oil, alpha-linolenic acid". http://www.nlm.nih.gov/medlineplus/print/druginfo/natural/patient-fishoil.html. Retrieved 26 March 2006. 
  2. ^ Willett WC (September 2007). "The role of dietary n-6 fatty acids in the prevention of cardiovascular disease.". http://www.ncbi.nlm.nih.gov/pubmed/17876199?dopt=Citation. Retrieved 16 March 2010. 
  3. ^ Yong Q. Chen, et 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. PMID 1890998. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1890998. Retrieved 2008-11-30. 
  4. ^ a b Valeria Pala, Vittorio Krogh, Paola Muti, Véronique Chajès, Elio Riboli, Andrea Micheli, Mitra Saadatian, Sabina Sieri, Franco Berrino (18 July 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. http://jnci.oxfordjournals.org/cgi/content/full/93/14/1088. Retrieved 2008-11-30. 
  5. ^ Veldink JH, Kalmijn S, Groeneveld GJ, Wunderink W, Koster A, de Vries JH, van der Luyt J, Wokke JH, Van den Berg LH (April 2007). "Intake of polyunsaturated fatty acids and vitamin E reduces the risk of developing amyotrophic lateral sclerosis". J. Neurol. Neurosurg. Psychiatr. 78 (4): 367–71. doi:10.1136/jnnp.2005.083378. PMID 16648143. http://jnnp.bmj.com/cgi/pmidlookup?view=long&pmid=16648143. Retrieved 2009-03-13. 
  6. ^ Okamoto K, Kihira T, Kondo T, Kobashi G, Washio M, Sasaki S, Yokoyama T, Miyake Y, Sakamoto N, Inaba Y, Nagai M (October 2007). "Nutritional status and risk of amyotrophic lateral sclerosis in Japan". Amyotroph Lateral Scler 8 (5): 300–4. doi:10.1080/17482960701472249. PMID 17852010. http://www.informaworld.com/openurl?genre=article&doi=10.1080/17482960701472249&magic=pubmed||1B69BA326FFE69C3F0A8F227DF8201D0. Retrieved 2009-03-13. 
  7. ^ Scislowski V, Bauchart D, Gruffat D, Laplaud PM, Durand D (2005). "Effect of dietary n-6 and n-3 polyunsaturated fatty acids on peroxidizability of lipoproteins in steers". Lipids 40 (12): 1245–56. doi:10.1007/s11745-005-1492-z. PMID 16477809. 
  8. ^ Diniz YS, Cicogna AC, Padovani CR, Santana LS, Faine LA, Novelli EL (2004). "Diets rich in saturated and polyunsaturated fatty acids: metabolic shifting and cardiac health". Nutrition 20 (2): 230–4. doi:10.1016/j.nut.2003.10.012. PMID 14962692. 
  9. ^ Quiles JL, Ochoa JJ, Huertas JR, Mataix J (2004). "Coenzyme Q supplementation protects from age-related DNA double-strand breaks and increases lifespan in rats fed on a PUFA-rich diet". Exp Gerontol. 39 (2): 189–94. doi:10.1016/j.exger.2003.10.002. PMID 15036411. 
  10. ^ 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. http://www3.interscience.wiley.com/journal/120780752/abstract. Retrieved 2008-11-30. 
  11. ^ Cite error: Invalid <ref> tag; no text was provided for refs named Yong_Q._Chen.2C_at_al_2007_1866; see Help:Cite error.
  12. ^ http://www.nal.usda.gov/fnic/foodcomp/search/
  13. ^ a b c .nutritiondata.com --> Egg, yolk, raw, fresh Retrieved on August 24, 2009
  14. ^ Feinberg School > Nutrition > Nutrition Fact Sheet: Lipids Northwestern University. Retrieved on August 24, 2009

External links


Simple English

Polyunsaturated fats are fats that are usually found in items like vegetable oils. Such items are typically found to be liquid at room temperature.

Chemistry

Polyunsaturated fats are called as organic compounds. Its molecules contains more than one double bonds. The peculiar structure reduces the strength of the forces between molecules. This causes the items to have a lower melting point. This is why the items are usually liquid at room temperature.

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