Polyunsaturated fatty acid

Short description: More than one unsaturation present in the hydrocarbon chain

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Types of fat]]s in food

* Saturated fat
* Unsaturated fat
* Monounsaturated fat
* ω−7
* ω−9
* Polyunsaturated fat
* ω−3
* ω−6
* Trans fat
* Interesterified fat

See also

* Fatty acid
* Essential fatty acid
* Conditionally essential fatty acid
* Triglyceride
* Cholesterol

* v
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* e

In biochemistry and nutrition, polyunsaturated fatty acids (abbreviated PUFAs, also called polyunsaturated fats) are fatty acids that contain more than one double bond in their backbone. This class includes many important compounds, such as essential fatty acids and those that give drying oils their characteristic property.

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.

## Contents

* 1 Chemical structure
* 2 Dietary sources
* 3 Types
* 3.1 Methylene-interrupted polyenes
* 3.1.1 Omega-3
* 3.1.2 Omega-6
* 3.1.3 Omega-9
* 3.2 Conjugated fatty acids
* 3.3 Other polyunsaturated fatty acids
* 4 Function and effects
* 5 Health
* 5.1 Potential benefits
* 5.2 Pregnancy
* 5.3 Cancer
* 6 Thermal degradation
* 7 See also
* 8 References
* 8.1 Citations
* 8.2 General References

## Chemical structure

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.

Polyunsaturated fatty acids can be classified in various groups by their chemical structure:

* methylene-interrupted polyenes
* conjugated fatty acids
* other PUFAs

Based on the length of their carbon backbone, they are sometimes classified in two groups:[3]

* short chain polyunsaturated fatty acids (SC-PUFA), with 18 carbon atoms
* long-chain polyunsaturated fatty acids (LC-PUFA) with 20 or more carbon atoms

## Dietary sources

## Types

### Methylene-interrupted polyenes

These fatty acids have 2 or more cis double bonds that are separated from each other by a single methylene bridge (-CH2-). This form is also sometimes called a divinylmethane pattern.[4]

Methylene- interrupted double bonds  −C−C=C−C−C=C−

The essential fatty acids are all omega-3 and -6 methylene-interrupted fatty acids. See more at Essential fatty acids--Nomenclature[5]

#### Omega-3

Common name  | Lipid name  | Chemical name

|
|

Omega-3 fatty acids, polyunsaturated  Hexadecatrienoic acid (HTA)  | 16:3 (n-3)  | all-cis 7,10,13-hexadecatrienoic acid
Alpha-linolenic acid (ALA)  | 18:3 (n-3)  | all-cis-9,12,15-octadecatrienoic acid
Stearidonic acid (SDA)  | 18:4 (n-3)  | all-cis-6,9,12,15,-octadecatetraenoic acid
Eicosatrienoic acid (ETE)  | 20:3 (n-3)  | all-cis-11,14,17-eicosatrienoic acid
Eicosatetraenoic acid (ETA)  | 20:4 (n-3)  | all-cis-8,11,14,17-eicosatetraenoic acid
Eicosapentaenoic acid (EPA, Timnodonic acid)  | 20:5 (n-3)  | all-cis-5,8,11,14,17-eicosapentaenoic acid
Heneicosapentaenoic acid (HPA)  | 21:5 (n-3)  | all-cis-6,9,12,15,18-heneicosapentaenoic acid
Docosapentaenoic acid (DPA, Clupanodonic acid)  | 22:5 (n-3)  | all-cis-7,10,13,16,19-docosapentaenoic acid
Docosahexaenoic acid (DHA, Cervonic acid)  | 22:6 (n-3)  | all-cis-4,7,10,13,16,19-docosahexaenoic acid
Tetracosapentaenoic acid  | 24:5 (n-3)  | all-cis-9,12,15,18,21-tetracosapentaenoic acid
Tetracosahexaenoic acid (Nisinic acid)  | 24:6 (n-3)  | all-cis-6,9,12,15,18,21-tetracosahexaenoic acid

#### Omega-6

Common name  | Lipid name  | Chemical name

|
|

Omega-6 fatty acids, polyunsaturated  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
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)  | 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 (AdA)  | 22:4 (n-6)  | all-cis-7,10,13,16-docosatetraenoic acid
Docosapentaenoic acid (DPA)  | 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

#### Omega-9

Common name  | Lipid name  | Chemical name

|
|

Omega-9 fatty acids, mono- and polyunsaturated  Oleic acid† | 18:1 (n-9)  | cis-9-octadecenoic acid
Eicosenoic acid† | 20:1 (n-9)  | cis-11-eicosenoic acid
Mead acid | 20:3 (n-9)  | all-cis-5,8,11-eicosatrienoic acid
Erucic acid† | 22:1 (n-9)  | cis-13-docosenoic acid
Nervonic acid† | 24:1 (n-9)  | cis-15-tetracosenoic acid
†Monounsaturated

### Conjugated fatty acids

Conjugated double bonds  -C=C-C=C-

Common name  | Lipid name  | Chemical name

|
|

Conjugated fatty acids have two or more conjugated double bonds Conjugated Linoleic Acids (two conjugated double bonds)
Rumenic acid | 18:2 (n-7)  | 9Z,11E-octadeca-9,11-dienoic acid
| 18:2 (n-6)  | 10E,12Z-octadeca-10,12-dienoic acid
Conjugated Linolenic Acids (three conjugated double bonds)
α-Calendic acid | 18:3 (n-6)  | 8E,10E,12Z-octadecatrienoic acid
β-Calendic acid | 18:3 (n-6)  | 8E,10E,12E-octadecatrienoic acid
Jacaric acid | 18:3 (n-6)  | 8Z,10E,12Z-octadecatrienoic acid
α-Eleostearic acid | 18:3 (n-5)  | 9Z,11E,13E-octadeca-9,11,13-trienoic acid
β-Eleostearic acid  | 18:3 (n-5)  | 9E,11E,13E-octadeca-9,11,13-trienoic acid
Catalpic acid | 18:3 (n-5)  | 9Z,11Z,13E-octadeca-9,11,13-trienoic acid
Punicic acid | 18:3 (n-5)  | 9Z,11E,13Z-octadeca-9,11,13-trienoic acid
Other
Rumelenic acid  | 18:3 (n-3)  | 9E,11Z,15E-octadeca-9,11,15-trienoic acid
α-Parinaric acid  | 18:4 (n-3)  | 9E,11Z,13Z,15E-octadeca-9,11,13,15-tetraenoic acid
β-Parinaric acid  | 18:4 (n-3)  | all trans-octadeca-9,11,13,15-tetraenoic acid
Bosseopentaenoic acid | 20:5 (n-6)  | 5Z,8Z,10E,12E,14Z-eicosapentaenoic acid

### Other polyunsaturated fatty acids

Common name  | Lipid name  | Chemical name

|
|

Pinolenic acid | 18:3 (n-6)  | (5Z,9Z,12Z)-octadeca-5,9,12-trienoic acid
Sciadonic acid | 20:3 (n-6)  | (5Z,11Z,14Z)-eicosa-5,11,14-trienoic acid

## Function and effects

The biological effects of the ω-3 and ω-6 fatty acids are largely mediated by their mutual interactions, see Essential fatty acid interactions for detail.

## 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.[6][7][8][9]

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.[10] Other preliminary research indicates that omega-6 fatty acids in sunflower oil and safflower oil may also reduce the risk of cardiovascular disease.[11]

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.[12] The DHA obtained through the consumption of polyunsaturated fatty acids is positively associated with cognitive and behavioral performance.[13] 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.[14] Although this evaluation was disputed by many scientists,[15] it fueled debate over worldwide dietary advice to substitute polyunsaturated fats for saturated fats.[16]

### 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.[10] 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.[10][17]

## Thermal degradation

Polyunsaturated fatty acids in culinary oils undergo oxidative deterioration at temperatures of 150 °C (302 °F). The heating causes a free radical chain reaction, which oxidizes the PUFAs into hydroperoxide, which further decomposes into a complex mixture of secondary products.[18]

## See also

* Fatty acid
* Essential fatty acid
* Saturated fat
* Unsaturated fat
* Monounsaturated fat
* Polyunsaturated fat

## References

### Citations

1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 "Essential Fatty Acids". Micronutrient Information Center, Oregon State University, Corvallis, OR. May 2014. http://lpi.oregonstate.edu/mic/other-nutrients/essential-fatty-acids.
2. ↑ "Omega-3 fatty acids, fish oil, alpha-linolenic acid". Mayo Clinic. 2017. http://www.mayoclinic.com/health/fish-oil/NS_patient-fishoil/.
3. ↑ "Selection in Europeans on Fatty Acid Desaturases Associated with Dietary Changes". Mol Biol Evol 34 (6): 1307–1318. 2017. doi:10.1093/molbev/msx103. PMID 28333262.
4. ↑ Baggott, James (1997). The divinylmethane pattern in fatty acids. Salt Lake City, UT: Knowledge Weavers.
5. ↑ "National nutrient database for standard reference, release 23". United States Department of Agriculture, Agricultural Research Service. 2011. http://www.nal.usda.gov/fnic/foodcomp/search/.
6. ↑ "Fats explained". https://www.heartuk.org.uk/downloads/factsheets/fats-explained.pdf. Retrieved 20 February 2019.
7. ↑ "Key Recommendations: Components of Healthy Eating Patterns". https://health.gov/dietaryguidelines/2015/guidelines/chapter-1/key-recommendations/. Retrieved 20 February 2019.
8. ↑ "Live Well, Eat well, Fat: the facts". https://www.nhs.uk/live-well/eat-well/different-fats-nutrition/. Retrieved 20 February 2019.
9. ↑ "Dietary Guidelines for Indians - A Manual". http://ninindia.org/DietaryGuidelinesforNINwebsite.pdf.
10. ↑ 10.0 10.1 10.2 "Omega-3 Fatty Acids and Health: Fact Sheet for Health Professionals". US National Institutes of Health, Office of Dietary Supplements. 2 November 2016. http://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/.
11. ↑ "The role of dietary n-6 fatty acids in the prevention of cardiovascular disease". Journal of Cardiovascular Medicine 8 Suppl 1: S42-5. September 2007. doi:10.2459/01.JCM.0000289275.72556.13. PMID 17876199.
12. ↑ "Erythrocyte membrane fatty acids and subsequent breast cancer: a prospective Italian study". Journal of the National Cancer Institute 93 (14): 1088–95. July 2001. doi:10.1093/jnci/93.14.1088. PMID 11459870.
13. ↑ "Effect of fish oil on cognitive performance in older subjects: a randomized, controlled trial". Neurology 71 (6): 430–8. August 2008. doi:10.1212/01.wnl.0000324268.45138.86. PMID 18678826.
14. ↑ "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. February 2013. doi:10.1136/bmj.e8707. PMID 23386268.
15. ↑ 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. https://www.hsph.harvard.edu/nutritionsource/2016/04/13/diet-heart-ramsden-mce-bmj-comments/.
16. ↑ "Omega-3 Polyunsaturated Fatty Acids: The Way Forward in Times of Mixed Evidence". BioMed Research International 2015: 143109. 2015. doi:10.1155/2015/143109. PMID 26301240.
17. ↑ "Marine fatty acid intake is associated with breast cancer prognosis". The Journal of Nutrition 141 (2): 201–6. February 2011. doi:10.3945/jn.110.128777. PMID 21178081.
18. ↑ Moya Moreno, MC; Mendoza Olivares, D; Amézquita López, FJ; Gimeno Adelantado, JV; Bosch Reig, F (September 13, 1999). "Analytical evaluation of polyunsaturated fatty acids degradation during thermal oxidation of edible oils by Fourier transform infrared spectroscopy.". Talanta 50 (2): 269–75. doi:10.1016/S0039-9140(99)00034-X. PMID 18967717.

### General References

* Cyberlipid. "Polyenoic Fatty Acids". http://www.cyberlipid.org/fa/acid0003.htm.

* Gunstone, Frank D. "Lipid Glossary 2". http://www.plantbiology.msu.edu/ohlrogge/labweb/lipid_glossary.pdf.

* "Common (non-systematic) Names for Fatty Acids". 2003-09-17. http://aocs.org/member/division/analytic/fanames.asp.

* Heinz; Roughan, PG (1983). "Similarities and Differences in Lipid Metabolism of Chloroplasts Isolated from 18:3 and 16:3 Plants". Plant Physiol 72 (2): 273–279. doi:10.1104/pp.72.2.273. PMID 16662992.

* v
* t
* e

Edible fats and oils

Fats|

| Pork fats|

* Fatback
* Lardo
* Salo
* Salt pork
* Szalonna
* Lard
* Lardon
* Pork belly
* Bacon
* Pancetta
* Tocino
* Speck

|

Beef/mutton fats|

* Dripping
* Suet
* Tallow
* Tail fat

Dairy fats|

* Butter
* Clarified butter
* Ghee
* Niter kibbeh
* Smen

Poultry fats|

* Chicken fat
* Duck fat
* Schmaltz

Other animal fats|

* Blubber
* Muktuk
* Whale oil

Vegetable fats|

* Borneo tallow
* Cocoa butter
* Mango butter
* Margarine
* Shea butter
* Vegetable shortening

Oils|

| Fish oils|

* Cod liver oil
* Shark liver oil

|

Vegetable oils|

| Major oils|

* Coconut oil
* Corn oil
* Cottonseed oil
* Olive oil
* Palm oil
* palm kernel oil
* Peanut oil
* Rapeseed oil
* Canola oil and Colza oil (toxic oil syndrome)
* Safflower oil
* Soybean oil
* Sunflower oil

|

Nut oils|

* Almond oil
* Argan oil
* Cashew oil
* Hazelnut oil
* Macadamia oil
* Marula oil
* Mongongo nut oil
* Pecan oil
* Pine nut oil
* Pistachio oil
* Walnut oil

Fruit and
seed oils|

* Ambadi seed oil
* Avocado oil
* Castor oil
* Grape seed oil
* Hemp oil
* Linseed oil (flaxseed oil)
* Mustard oil
* Olive oil
* Perilla oil
* Poppyseed oil
* Pumpkin seed oil
* Rice bran oil
* Sesame oil
* Tea seed oil
* Watermelon seed oil

See also
List of vegetable oils
Cooking oil
Essential oil

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