Editing Unsaturated fat

{{short description|Fat or fatty acid in which there is at least one double bond within the fatty acid chain}}
{{Fats}}
An '''unsaturated fat''' is a [[fat]] or [[fatty acid]] in which there is at least one [[double bond]] within the fatty acid chain. A fatty acid chain is [[Monounsaturated fat|monounsaturated]] if it contains one double bond, and [[polyunsaturated fat|polyunsaturated]] if it contains more than one double bond.

A [[saturated fat]] has no carbon-to-carbon double bonds, so the maximum possible number of hydrogen is bonded to carbon, and thus, is considered to be "saturated" with hydrogen atoms. To form carbon-to-carbon double bonds, [[hydrogen]] [[atom]]s are removed from the carbon chain. In cellular [[metabolism]], unsaturated fat molecules contain less energy (i.e., fewer [[calories]]) than an equivalent amount of saturated fat. The greater the degree of unsaturation in a fatty acid (i.e., the more double bonds in the fatty acid) the more susceptible it becomes to [[lipid peroxidation]] ([[rancidification|rancidity]]). [[Antioxidant]]s can protect unsaturated fat from lipid peroxidation.

==Composition of common fats==

In chemical analysis, fats are broken down to their constituent fatty acids, which can be analyzed in various ways.  In one approach, fats undergo [[transesterification]] to give [[fatty acid methyl ester]]s (FAMEs), which are amenable to separation and quantitation using [[gas chromatography]].<ref>{{cite journal | vauthors = Aizpurua-Olaizola O, Ormazabal M, Vallejo A, Olivares M, Navarro P, Etxebarria N, Usobiaga A | display-authors = 6 | title = Optimization of supercritical fluid consecutive extractions of fatty acids and polyphenols from Vitis vinifera grape wastes | journal = Journal of Food Science | volume = 80 | issue = 1 | pages = E101-7 | date = January 2015 | pmid = 25471637 | doi = 10.1111/1750-3841.12715 }}</ref> Classically, unsaturated isomers were separated and identified by argentation thin-layer chromatography.<ref>{{cite journal | vauthors = Breuer B, Stuhlfauth T, Fock HP | title = Separation of fatty acids or methyl esters including positional and geometric isomers by alumina argentation thin-layer chromatography | journal = Journal of Chromatographic Science | volume = 25 | issue = 7 | pages = 302–6 | date = July 1987 | pmid = 3611285 | doi = 10.1093/chromsci/25.7.302 }}</ref>

{| class="wikitable"
|+ Fatty acid component (mole %) of selected fats<ref>{{cite book |doi=10.1002/14356007.a10_173 |chapter=Fats and Fatty Oils |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2000 |last1=Thomas |first1=Alfred |isbn=9783527303854 }}</ref>
|-
!fat source!!saturated !!monounsaturated !! doubly unsaturated !! triunsaturated
|-
| [[Palm kernel]] || 60–65 ||10–18 || 1–3|| trace
|-
| [[Cottonseed oil]] || 23–30 || 14–21 || 45–58|| trace
|-
| [[Corn oil]]  || 10–15 || 25–35 || 40–60|| trace
|-
| [[Linseed oil]]  || 8–11 || 18–26 || 14–20|| 51–56
|-
| [[Soybean oil]] || 11–17 || 18–25 || 49–57|| 6–11
|-
| [[Peanut oil]]  || 12–17 || 35–42 ||39–44|| trace
|-
| [[Lard]] || 36–48 || 36–52||10–12|| 1
|-
| [[Beef tallow]]  || 43–64 || 26–45|| 2–6|| 1
|}
The saturated fatty acid components are almost exclusively stearic (C18) and [[palmitic acid]]s (C16). Monounsaturated fats are almost exclusively [[oleic acid]]. [[Linolenic acid]] comprises most of the triunsaturated fatty acid component.
<!--{{Fat composition in different foods}} no good sources-->

== Chemistry and nutrition ==
[[File:Fatchart.svg|thumb|right|Amounts of fat types in selected foods]]

Although polyunsaturated fats are protective against [[cardiac arrhythmia]]s, a study of post-[[menopausal]] women with a relatively low fat intake showed that polyunsaturated fat is positively associated with progression of [[coronary]] [[atherosclerosis]], whereas [[monounsaturated fat]] is not.<ref>{{cite journal | vauthors = Mozaffarian D, Rimm EB, Herrington DM | title = Dietary fats, carbohydrate, and progression of coronary atherosclerosis in postmenopausal women | journal = The American Journal of Clinical Nutrition | volume = 80 |  issue = 5 | pages = 1175–84 | date = November 2004 | pmid = 15531663 | pmc = 1270002 | doi = 10.1093/ajcn/80.5.1175 }}</ref> This probably is an indication of the greater vulnerability of polyunsaturated fats to [[lipid peroxidation]], against which [[vitamin E|vitamin&nbsp;E]] has been shown to be protective.<ref>{{cite journal | vauthors = Leibovitz B, Hu ML, Tappel AL | title = Dietary supplements of vitamin E, beta-carotene, coenzyme Q10 and selenium protect tissues against lipid peroxidation in rat tissue slices | journal = The Journal of Nutrition | volume = 120 | issue = 1 | pages = 97–104 | date = January 1990 | pmid = 2303916 | doi = 10.1093/jn/120.1.97 | doi-access = free }}</ref>

Examples of unsaturated fatty acids are [[palmitoleic acid]], [[oleic acid]], [[myristoleic acid]], [[linoleic acid]], and [[arachidonic acid]]. Foods containing unsaturated fats include [[avocado]], [[nut (fruit)|nuts]], [[olive oil]]s, and [[vegetable oil]]s such as [[canola]]. [[Meat]] products contain both saturated and unsaturated fats.

Although unsaturated fats are conventionally regarded as 'healthier' than saturated fats,<ref>[https://www.bbc.co.uk/health/treatments/healthy_living/nutrition/healthy_fatsugar.shtml Fats and sugars]. BBC Health, retrieved 2013-04-07</ref> the United States [[Food and Drug Administration]] (FDA) recommendation stated that the amount of unsaturated fat consumed should not exceed 30% of one's daily caloric intake.<ref>{{Cite web |title=Fat Facts, the Right Amount for a Healthy Diet |url=https://extension.psu.edu/fat-facts-the-right-amount-for-a-healthy-diet |access-date=2024-06-03 |website=extension.psu.edu |language=en}}</ref> Most foods contain both unsaturated and saturated fats. Marketers{{who|date=March 2025}} advertise only one or the other, depending on which one makes up the majority. Thus, various unsaturated fat vegetable oils, such as olive oils, also contain saturated fat.<ref name="pmid8781757">{{cite journal | vauthors = Storlien LH, Baur LA, Kriketos AD, Pan DA, Cooney GJ, Jenkins AB, Calvert GD, Campbell LV | display-authors = 6 | title = Dietary fats and insulin action | journal = Diabetologia | volume = 39 | issue = 6 | pages = 621–31 | date = June 1996 | pmid = 8781757 | doi = 10.1007/BF00418533 | s2cid = 33171616 }}</ref>

== Membrane composition as a metabolic pacemaker ==
Studies on the [[cell membrane]]s of [[mammal]]s and [[reptile]]s discovered that mammalian cell membranes are composed of a higher proportion of polyunsaturated fatty acids ([[Docosahexaenoic acid|DHA]], [[omega-3 fatty acid]]) than [[reptile]]s.<ref name="HulbertElse1999">{{cite journal | vauthors = Hulbert AJ, Else PL | title = Membranes as possible pacemakers of metabolism | journal = Journal of Theoretical Biology | volume = 199 | issue = 3 | pages = 257–74 | date = August 1999 | pmid = 10433891 | doi = 10.1006/jtbi.1999.0955 | bibcode = 1999JThBi.199..257H }}</ref> Studies on bird fatty acid composition have noted similar proportions to mammals but with 1/3rd less omega-3 fatty acids as compared to [[omega-6 fatty acid|omega-6]] for a given body size.<ref name="Hulbertetal2002">{{cite journal | vauthors = Hulbert AJ, Faulks S, Buttemer WA, Else PL | title = Acyl composition of muscle membranes varies with body size in birds | journal = The Journal of Experimental Biology | volume = 205 | issue = Pt 22 | pages = 3561–9 | date = November 2002 | doi = 10.1242/jeb.205.22.3561 | pmid = 12364409 }}</ref> This fatty acid composition results in a more fluid cell membrane but also one that is permeable to various ions (H+ & Na+), resulting in cell membranes that are more costly to maintain. This maintenance cost has been argued to be one of the key causes for the high metabolic rates and concomitant [[warm-blooded]]ness of mammals and birds.<ref name="HulbertElse1999" /> However polyunsaturation of cell membranes may also occur in response to chronic cold temperatures as well. In [[fish]] increasingly cold environments lead to increasingly high cell membrane content of both monounsaturated and polyunsaturated fatty acids, to maintain greater membrane fluidity (and functionality) at the lower [[temperature]]s.<ref>{{cite journal | vauthors = Hulbert AJ | title = Life, death and membrane bilayers | journal = The Journal of Experimental Biology | volume = 206 | issue = Pt 14 | pages = 2303–11 | date = July 2003 | pmid = 12796449 | doi = 10.1242/jeb.00399 | doi-access = free }}</ref><ref name="RaynardCossins1991">{{cite journal | vauthors = Raynard RS, Cossins AR | title = Homeoviscous adaptation and thermal compensation of sodium pump of trout erythrocytes | journal = The American Journal of Physiology | volume = 260 | issue = 5 Pt 2 | pages = R916–24 | date = May 1991 | pmid = 2035703 | doi = 10.1152/ajpregu.1991.260.5.R916 | s2cid = 24441498 }}</ref>

== See also ==
{{Wiktionary}}
* [[Iodine value]] – a chemical analysis method to determine the proportion of unsaturated fat.
* [[List of unsaturated fatty acids]]

== References ==
{{Reflist|30em}}

{{lipids}}

[[Category:Fatty acids|#]]
[[Category:Food science]]
[[Category:Lipids]]
[[Category:Nutrition]]
[[Category:Edible oil chemistry]]