Polyunsaturated fatty acid

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Types of fats in food
Components
Manufactured fats

Polyunsaturated fats are fats in which the constituent hydrocarbon chain possesses two or more carbon–carbon double bonds.[1][2] Polyunsaturated fat can be found mostly in nuts, seeds, fish, seed oils, and oysters.[1] "Unsaturated" refers to the fact that the molecules contain less than the maximum amount of hydrogen (if there were no double bonds). These materials exist as cis or trans isomers depending on the geometry of the double bond.

Saturated fats have hydrocarbon chains which can be most readily aligned. The hydrocarbon chains in trans fats align more readily than those in cis fats, but less well than those in saturated fats. In general, this means that the melting points of fats increase from cis to trans unsaturated and then to saturated. See the section about the chemical structure of fats for more information.

Chemical structure of the polyunsaturated fat linoleic acid.
3D representation of linoleic acid in a bent conformation.
Chemical structure of alpha-linolenic acid (ALA), an essential omega−3 fatty acid.

The position of the carbon-carbon double bonds in carboxylic acid chains in fats is designated by Greek letters.[1] The carbon atom closest to the carboxyl group is the alpha carbon, the next carbon is the beta carbon and so on. In fatty acids the carbon atom of the methyl group at the end of the hydrocarbon chain 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.

While it is the nutritional aspects of polyunsaturated fats that are generally of greatest interest, these materials also have non-food applications. Drying oils, which polymerize on exposure to oxygen to form solid films, are polyunsaturated fats. The most common ones are linseed (flax seed) oil, tung oil, poppy seed oil, perilla oil, and walnut oil. These oils are used to make paints and varnishes.

Health

Potential benefits

Because of their effects in the diet, unsaturated fats (monounsaturated and polyunsaturated) are often referred to as good fats; while saturated fats are sometimes referred to as bad fats. Some fat is needed in the diet, but it is usually considered that fats should not be consumed excessively, unsaturated fats should be preferred, and saturated fats in particular should be limited.[3][4][5][6]

In preliminary research, omega-3 fatty acids in algal oil, fish oil, fish and seafood have been shown to lower the risk of heart attacks.[7] Other preliminary research indicates that omega-6 fatty acids in sunflower oil and safflower oil may also reduce the risk of cardiovascular disease.[8]

Among omega-3 fatty acids, neither long-chain nor short-chain forms were consistently associated with breast cancer risk. High levels of docosahexaenoic acid (DHA), however, the most abundant omega-3 polyunsaturated fatty acid in erythrocyte (red blood cell) membranes, were associated with a reduced risk of breast cancer.[9] The DHA obtained through the consumption of polyunsaturated fatty acids is positively associated with cognitive and behavioral performance.[10] In addition DHA is vital for the grey matter structure of the human brain, as well as retinal stimulation and neurotransmission.[1]

Contrary to conventional advice, an evaluation of evidence from 1966-1973 pertaining to the health impacts of replacing dietary saturated fat with linoleic acid found that participants in the group doing so had increased rates of death from all causes, coronary heart disease, and cardiovascular disease.[11] Although this evaluation was disputed by many scientists,[12] it fueled debate over worldwide dietary advice to substitute polyunsaturated fats for saturated fats.[13]

Pregnancy

Polyunsaturated fat supplementation does not decrease the incidence of pregnancy-related disorders, such as hypertension or preeclampsia, but may increase the length of gestation slightly and decreased the incidence of early premature births.[1]

Expert panels in the United States and Europe recommend that pregnant and lactating women consume higher amounts of polyunsaturated fats than the general population to enhance the DHA status of the fetus and newborn.[1]

Cancer

Results from observational clinical trials on polyunsaturated fat intake and cancer have been inconsistent and vary by numerous factors of cancer incidence, including gender and genetic risk.[7] Some studies have shown associations between higher intakes and/or blood levels of polyunsaturated fat omega-3s and a decreased risk of certain cancers, including breast and colorectal cancer, while other studies found no associations with cancer risk.[7][14]

Food sources

Food sources of polyunsaturated fats include:[1][15]

Food source (100g) Polyunsaturated fat (g)
Walnuts 47
Canola Oil 34
Sunflower seeds 33
Sesame Seeds 26
Chia Seeds 23.7
Unsalted Peanuts 16
Peanut Butter 14.2
Avocado Oil 13.5 [16]
Olive Oil 11
Safflower Oil 12.82[17]
Seaweed 11
Sardines 5
Soybeans 7
Tuna 14
Wild Salmon 17.3
Whole Grain Wheat 9.7
Fat composition in different foods
Food Saturated Mono-
unsaturated		 Poly-
unsaturated
As weight percent (%) of total fat
Cooking oils
Algal oil[18] 4 92 4
Canola[19] 8 64 28
Coconut oil 87 13 0
Corn oil 13 24 59
Cottonseed oil[19] 27 19 54
Olive oil[20] 14 73 11
Palm kernel oil[19] 86 12 2
Palm oil[19] 51 39 10
Peanut oil[21] 17 46 32
Rice bran oil 25 38 37
Safflower oil, high oleic[22] 6 75 14
Safflower oil, linoleic[19][23] 6 14 75
Soybean oil 15 24 58
Sunflower oil[24] 11 20 69
Mustard oil 11 59 21
Dairy products
Butterfat[19] 66 30 4
Cheese, regular 64 29 3
Cheese, light 60 30 0
Ice cream, gourmet 62 29 4
Ice cream, light 62 29 4
Milk, whole 62 28 4
Milk, 2% 62 30 0
Whipping cream[25]* 66 26 5
Meats
Beef 33 38 5
Ground sirloin 38 44 4
Pork chop 35 44 8
Ham 35 49 16
Chicken breast 29 34 21
Chicken 34 23 30
Turkey breast 30 20 30
Turkey drumstick 32 22 30
Fish, orange roughy 23 15 46
Salmon 28 33 28
Hot dog, beef 42 48 5
Hot dog, turkey 28 40 22
Burger, fast food 36 44 6
Cheeseburger, fast food 43 40 7
Breaded chicken sandwich 20 39 32
Grilled chicken sandwich 26 42 20
Sausage, Polish 37 46 11
Sausage, turkey 28 40 22
Pizza, sausage 41 32 20
Pizza, cheese 60 28 5
Nuts
Almonds dry roasted 9 65 21
Cashews dry roasted 20 59 17
Macadamia dry roasted 15 79 2
Peanut dry roasted 14 50 31
Pecans dry roasted 8 62 25
Flaxseeds, ground 8 23 65
Sesame seeds 14 38 44
Soybeans 14 22 57
Sunflower seeds 11 19 66
Walnuts dry roasted 9 23 63
Sweets and baked goods
Candy, chocolate bar 59 33 3
Candy, fruit chews 14 44 38
Cookie, oatmeal raisin 22 47 27
Cookie, chocolate chip 35 42 18
Cake, yellow 60 25 10
Pastry, Danish 50 31 14
Fats added during cooking or at the table
Butter, stick 63 29 3
Butter, whipped 62 29 4
Margarine, stick 18 39 39
Margarine, tub 16 33 49
Margarine, light tub 19 46 33
Lard 39 45 11
Shortening 25 45 26
Chicken fat 30 45 21
Beef fat 41 43 3
Goose fat[26] 33 55 11
Dressing, blue cheese 16 54 25
Dressing, light Italian 14 24 58
Other
Egg yolk fat[27] 36 44 16
Avocado[28] 16 71 13
Unless else specified in boxes, then reference is:[citation needed]
* 3% is trans fats

References

  1. ^ a b c d e f g "Essential Fatty Acids". Micronutrient Information Center, Oregon State University, Corvallis, OR. May 2014. Retrieved 24 May 2017.
  2. ^ "Omega-3 fatty acids, fish oil, alpha-linolenic acid". Mayo Clinic. 2017. Retrieved 24 May 2017.
  3. ^ "Fats explained" (PDF). HEART UK – The Cholesterol Charity. Retrieved 20 February 2019.
  4. ^ "Key Recommendations: Components of Healthy Eating Patterns". Dietary Guidelines 2015-2020. Retrieved 20 February 2019.
  5. ^ "Live Well, Eat well, Fat: the facts". NHS. Retrieved 20 February 2019.
  6. ^ "Dietary Guidelines for Indians - A Manual" (PDF). Indian Council of Medical Research, National Institute of Nutrition. Archived from the original (PDF) on 2018-12-22. Retrieved 2019-02-20.
  7. ^ a b c "Omega-3 Fatty Acids and Health: Fact Sheet for Health Professionals". US National Institutes of Health, Office of Dietary Supplements. 2 November 2016. Retrieved 5 April 2017.
  8. ^ Willett WC (September 2007). "The role of dietary n-6 fatty acids in the prevention of cardiovascular disease". Journal of Cardiovascular Medicine. 8 Suppl 1: S42-5. doi:10.2459/01.JCM.0000289275.72556.13. PMID 17876199.
  9. ^ Pala V, Krogh V, Muti P, Chajès V, Riboli E, Micheli A, Saadatian M, Sieri S, Berrino F (July 2001). "Erythrocyte membrane fatty acids and subsequent breast cancer: a prospective Italian study". Journal of the National Cancer Institute. 93 (14): 1088–95. doi:10.1093/jnci/93.14.1088. PMID 11459870.
  10. ^ van de Rest O, Geleijnse JM, Kok FJ, van Staveren WA, Dullemeijer C, Olderikkert MG, Beekman AT, de Groot CP (August 2008). "Effect of fish oil on cognitive performance in older subjects: a randomized, controlled trial". Neurology. 71 (6): 430–8. doi:10.1212/01.wnl.0000324268.45138.86. PMID 18678826.
  11. ^ Ramsden CE, Zamora D, Leelarthaepin B, Majchrzak-Hong SF, Faurot KR, Suchindran CM, Ringel A, Davis JM, Hibbeln JR (February 2013). "Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis". BMJ. 346: e8707. doi:10.1136/bmj.e8707. PMC 4688426. PMID 23386268.
  12. ^ Interview: Walter Willett (2017). "Research Review: Old data on dietary fats in context with current recommendations: Comments on Ramsden et al. in the British Medical Journal". TH Chan School of Public Health, Harvard University, Boston. Retrieved 24 May 2017.
  13. ^ Weylandt KH, Serini S, Chen YQ, Su HM, Lim K, Cittadini A, Calviello G (2015). "Omega-3 Polyunsaturated Fatty Acids: The Way Forward in Times of Mixed Evidence". BioMed Research International. 2015: 143109. doi:10.1155/2015/143109. PMC 4537707. PMID 26301240.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  14. ^ Patterson RE, Flatt SW, Newman VA, Natarajan L, Rock CL, Thomson CA, Caan BJ, Parker BA, Pierce JP (February 2011). "Marine fatty acid intake is associated with breast cancer prognosis". The Journal of Nutrition. 141 (2): 201–6. doi:10.3945/jn.110.128777. PMC 3021439. PMID 21178081.
  15. ^ "National nutrient database for standard reference, release 23". United States Department of Agriculture, Agricultural Research Service. 2011. Archived from the original on 2015-03-03. Retrieved 2009-02-22.
  16. ^ "Vegetable oil, avocado Nutrition Facts & Calories". nutritiondata.self.com.
  17. ^ "United States Department of Agriculture – National Nutrient Database". 8 September 2015.
  18. ^ "Thrive Culinary Algae Oil". Retrieved 7 January 2019.
  19. ^ a b c d e f Anderson D. "Fatty acid composition of fats and oils" (PDF). Colorado Springs: University of Colorado, Department of Chemistry. Retrieved April 8, 2017.
  20. ^ "NDL/FNIC Food Composition Database Home Page". United States Department of Agriculture, Agricultural Research Service. Retrieved May 21, 2013.
  21. ^ "Basic Report: 04042, Oil, peanut, salad or cooking". USDA. Archived from the original on March 9, 2016. Retrieved 16 January 2015.
  22. ^ "Oil, vegetable safflower, oleic". nutritiondata.com. Condé Nast. Retrieved 10 April 2017.
  23. ^ "Oil, vegetable safflower, linoleic". nutritiondata.com. Condé Nast. Retrieved 10 April 2017.
  24. ^ "Oil, vegetable, sunflower". nutritiondata.com. Condé Nast. Retrieved 27 September 2010.
  25. ^ USDA Basic Report Cream, fluid, heavy whipping
  26. ^ "Nutrition And Health". The Goose Fat Information Service.
  27. ^ "Egg, yolk, raw, fresh". nutritiondata.com. Condé Nast. Retrieved 24 August 2009.
  28. ^ "09038, Avocados, raw, California". National Nutrient Database for Standard Reference, Release 26. United States Department of Agriculture, Agricultural Research Service. Archived from the original on January 10, 2014. Retrieved 14 August 2014.
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