Alpha-linolenic acid
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2008-06-27T05:34:52Z
130.216.57.75
/* Dietary sources */
{{Chembox new
| Name = α-Linolenic acid
| ImageFile = Linolenic-acid-3D-vdW.png
| ImageFile1 = ALAnumbering.png
| ImageSize1 = 350px
| OtherNames = ALA; Linolenic acid; cis, cis,cis-9,12,15-Octadecatrienoic acid; (Z,Z,Z)-9,12,15-Octadecatrienoic acid; Industrene 120
| Section1 = {{Chembox Identifiers
| CASNo = 463-40-1
}}
| Section2 = {{Chembox Properties
| Formula = C<sub>18</sub>H<sub>30</sub>O<sub>2</sub>
| MolarMass = 278.43 g//mol
| Density =
| MeltingPt =
| BoilingPt =
}}
}}
'''[[alpha (letter)|α]]-Linolenic acid''' ('''ALA''') is an organic compound found in many common [[Vegetable fats and oils|vegetable oils]]. [[IUPAC nomenclature of organic chemistry|Systematically]], it is named ''all''-''cis''-9,12,15-octadecatrienoic acid.<ref name=Beare>{{cite web
|author=Beare-Rogers
|title=IUPAC Lexicon of Lipid Nutrition
|year=2001
|url=http://www.iupac.org/publications/pac/2001/pdf/7304x0685.pdf
|accessmonthday=22 February | accessyear=2006
|format=pdf}}</ref> In physiological literature, it is given the name 18:3 (''n''−3).
ALA is a [[carboxylic acid]] with an 18-carbon chain and three ''[[cis]]'' double bonds. The first double bond is located at the third carbon from the ''n'' end. Thus, ALA is a [[polyunsaturated fatty acid|polyunsaturated]] [[omega-3 fatty acid|''n''−3]] (omega-3) fatty acid. It is an isomer of [[γ-linolenic acid]], a polyunsaturated [[omega-6 fatty acid|''n''−6]] (omega-6) fatty acid.
==Dietary sources==
[[Image:Beklädnadsväxter, Linum usitatissimum, Nordisk familjebok.png|thumb|120px|right|Flax is a rich source of ALA.]]
Seed oils are the richest sources of ALA, notably those of [[rapeseed]] ([[canola]]), [[soybeans]], [[walnuts]], [[flaxseed]] (Linseed), [[Perilla oil|perilla]], [[chia]] and [[hemp]]. ALA is also obtained from the [[thylakoid|thylakoid membranes]] of the green leaves of broadleaf plants (the membranes responsible for photosynthesis).<ref>{{cite journal
|author= Chapman, David J.; De-Felice, John and Barber, James
|journal=Plant Physiol |year=1983 |month=May|volume=72 | issue=1|pages=225–228
|title=Growth Temperature Effects on Thylakoid Membrane Lipid and Protein Content of Pea Chloroplasts 1
|url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1066200
|accessdate=2007-01-15
|pmid=16662966}}</ref> Greens, therefore, and animals that eat greens, are often a good source of ALA.
{| class="wikitable" border=1 cellspacing=0 cellpadding=1 style="border-collapse:collapse;"
!|Common name||Alternate name||Linnaean name||% ALA<sup>†</sup>||ref.
|-
|[[Chia seed|Chia]] ||chia sage||''Salvia hispanica''||64% ||<ref name=sofadb> [http://www.bagkf.de/sofa/ Seed Oil Fatty Acids - SOFA Database Retrieval]</ref>
|-
|[[Kiwifruit|Kiwifruit]]||Chinese gooseberry||''Actinidia chinensis''||62%||<ref name=sofadb />
|-
|[[Perilla]]||shiso||''Perilla frutescens''||58%||<ref name=sofadb />
|-
|[[Flax]]||linseed||''Linum usitatissimum''||55%||<ref name=sofadb />
|-
|[[Cowberry|Lingonberry]]||cowberry||''Vaccinium vitis-idaea''||49%||<ref name=sofadb />
|-
|[[Portulaca|Purslane]]||portulaca||''Portulaca oleracea''||35%||<ref name=sofadb />
|-
| [[Sea Buckthorn]] ||seaberry ||''Hippophae rhamnoides L.''||32%||<ref name=Li>{{cite conference
| first = Thomas S. C.
| last = Li
| authorlink =
| coauthors =
| title = Sea buckthorn: New crop opportunity
| booktitle = Perspectives on new crops and new uses
| pages = 335–337
| publisher = [[ASHS Press]]
| date = 1999
| location = Alexandria, VA
| url = http://www.hort.purdue.edu/newcrop/proceedings1999/v4-335.html
| doi =
| id =
| accessdate = 2006-10-28}}</ref>
|-
|[[Hemp]]||cannabis||''Cannabis sativa''||20%||<ref name=sofadb />
|-
| [[Rapeseed]]||canola||''Brassica napus''||10%||<ref name=Beare />
|-
| [[Soybean#Oil|Soybean]] ||soya||''Glycine max''||8%||<ref name=Beare />
|-
| colspan=3|
| colspan=2|<small><sup>†</sup>average val</small>
|}
==Role in nutrition and health==
ALA, an ''n''−3 fatty acid, is a member of the group of [[essential fatty acids]], so called because they cannot be produced within the body and must be acquired through diet. Most seeds and seed oils are much richer in an ''n''−6 fatty acid, [[linoleic acid]]. Linoleic acid is also an essential fat, but it, and the other ''n''−6 fats, compete with ''n''−3s for positions in cell membranes and have very different effects on human health. ''(See [[Essential fatty acid interactions]].'')
[[Eicosapentaenoic acid]] (EPA; 20:5, ''n''−3) and [[docosahexaenoic acid]] (DHA; 22:6, ''n''−3) play a vital role in many metabolic processes. Although these two fatty acids are readily available from fish, these marine-derived fatty acids can also be synthesized by humans from ALA. Humans, however, can obtain ALA only through their diets, because the absence of the required 12- and 15-desaturase enzymes makes de novo synthesis from stearic acid impossible. Furthermore, conversion of dietary ALA into EPA is limited. Because the efficacy of ''n''−3 long-chain polyunsaturated fatty acid (LC-PUFA) synthesis decreases down the cascade of ALA conversion, DHA synthesis from ALA is even more restricted than that of EPA.<ref>{{cite journal
| author=Shiels M. Innis
| year = 2007
| title = Fatty acids and early human development
| journal = Early Human Development
| volume = 83
| pages = 761–766
| doi = 10.1016/j.earlhumdev.2007.09.004
}}</ref>
It is generally assumed that linoleic acid (LA; 18:2, ''n''−6) reduces EPA synthesis because of the competition between ALA and LA for common desaturation and elongation enzymes.{{Fact|date=March 2008}}
Studies have found evidence that ALA is related to a lower risk of cardiovascular disease.<ref>{{cite journal
| author = Penny M. Kris-Etherton, William S. Harris, [and] Lawrence J. Appel, for the Nutrition Committee
| year = 2002
| title = Fish Consumption, Fish Oil, Omega-3 Fatty Acids, and Cardiovascular Disease
| journal = Circulation
| volume = 106
| issue = 21
| pages = 2747–2757
| url = http://circ.ahajournals.org/cgi/content/full/106/21/2747
| format=pdf
| accessdate = 2006-07-25
| doi = 10.1161/01.CIR.0000038493.65177.94
| pmid = 12438303
}} PMID 12438303</ref><ref>{{cite journal
| author = William E. Connor
| year = 2000
| title = Importance of ''n''−3 fatty acids in health and disease
| journal = American Journal of Clinical Nutrition
| volume = 71
| issue = 1 Suppl.
| pages = 171S–175S
| url = http://www.ajcn.org/cgi/reprint/71/1/171S
| format=pdf
| accessdate = 2006-07-25
}} PMID 10617967</ref>
However, the mechanism is still unclear: The body converts ALA into the longer chain fatty acids EPA and DHA, and it is unknown whether the protective effect against [[cardiac arrhythmia]] is exerted by ALA itself, or by these [[metabolism|metabolic]] products. Some studies have linked ALA with rapidly progressing [[prostate cancer]]<ref>{{cite journal
| author = Brouwer IA, Katan MB, Zock PL
| year = 2004
| title = Dietary α-linolenic acid is associated with reduced risk of fatal coronary heart disease, but increased prostate cancer risk: a meta-analysis.
| journal = Journal of Nutrition
| volume = 134
| issue = 4
| pages = 919–922
| url = http://jn.nutrition.org/cgi/content/full/134/4/919
| accessdate = 2006-11-13
| pmid = 15051847
}} PMID 15051847</ref> and [[macular degeneration]],<ref>{{cite journal
| author = Eunyoung Cho, Shirley Hung, Walter C Willett, Donna Spiegelman, Eric B Rimm, Johanna M Seddon, Graham A Colditz and Susan E Hankinson
| year = 2001
| title = Prospective study of dietary fat and the risk of age-related macular degeneration
| journal = American Journal of Clinical Nutrition
| volume = 73
| issue = 2
| pages = 209–218
| url = http://www.ajcn.org/cgi/content/full/73/2/209
| accessdate = 2006-11-13
| pmid = 11157315
}} PMID 11157315</ref>
increasing the risk 70% over control subjects (over those that did not receive ALA). Research has also suggested a major neuroprotective effect of ALA in [[in vivo|in-vivo]] models of both global [[ischemia]] and KA-induced [[epilepsy]].<ref>{{cite journal
| author = Inger Lauritzen, Nicolas Blondeau, Catherine Heurteaux, Catherine Widmann, Georges Romey and Michel Lazdunski
| year = 2000
| title = Polyunsaturated fatty acids are potent neuroprotectors
| journal = The EMBO Journal
| volume = 19
| issue = 8
| pages = 1784–1793
| url = http://embojournal.npgjournals.com/cgi/content/full/19/8/1784
| accessdate = 2005-10-06
| pmid = 10775263
| doi = 10.1093/emboj/19.8.1784}}</ref>
A large 2006 study found no association between total ALA intake and overall risk of prostate cancer.<ref name="pmid16783606">{{cite journal |author=Koralek DO, Peters U, Andriole G, ''et al'' |title=A prospective study of dietary α-linolenic acid and the risk of prostate cancer (United States) |journal=Cancer Causes Control |volume=17 |issue=6 |pages=783–791 |year=2006 |pmid=16783606 |doi=10.1007/s10552-006-0014-x |accessdate=2007-11-14}}</ref>
===ALA===
When partially [[Hydrogenation|hydrogenated]], all unsaturated fatty acids form [[trans fats]]. [[Soybean]]s are the largest source of [[Vegetable fats and oils|edible oils]] in the U.S., and 40% of soy oil production is partially hydrogenated.<ref>{{cite journal
| url = http://www.truthabouttrade.org/article.asp?id=6669
| title = Ban on trans fat could benefit Iowa
| journal = Truth About Trade and Technology
| accessdate = January 3
| author = Fitzgerald, Anne and Brasher, Philip
| accessyear = 2007}}</ref><ref>{{cite web|
|author = Kinney, Tony
| title= Metabolism in Plants to Produce Healthier Food Oils (slide #2)
| url= http://www.metabolicengineering.gov/me2005/Kinney.pdf
| accessdate= 2007-01-11}}</ref> The low oxidative stability of ALA is one reason that [[soybean oil]] undergoes partial hydrogenation. Regulations forcing the [[Trans fats#Public response and regulation|listing or banning of trans fats]] have spurred the development of low-ALA soybeans. These yield a more stable oil requiring hydrogenation less often, and therefore providing trans-free alternatives into many applications such as frying oil.<ref>{{cite web
| url =http://www.monsanto.com/monsanto/layout/media/06/01-12-06.asp
| author = Monsanto
| title = ADM To Process Monsanto's VISTIVE Low Linolenic Soybeans At Indiana Facility
| accessdate = 2007-01-06}}</ref>
Several consortia are bringing low-ALA soy to market. [[DuPont]]'s effort involves [[Gene silencing|silencing]] the FAD2 gene that codes for [[Desaturase|Δ<sup>6</sup>-desaturase]], giving a soy oil with very low levels of both ALA and LA.<ref>{{cite web|
|author = Kinney, Tony
| title= Metabolism in Plants to Produce Healthier Food Oils
| url= http://www.metabolicengineering.gov/me2005/Kinney.pdf
| accessdate= 2007-01-11}}</ref>
===Cardiovascular===
Dietary ALA has been assessed for its role in cardiovascular health. Clinical benefits have been seen in some but not all studies. Still, a review in 2005 concluded "The weight of the evidence favors recommendations for modest dietary consumption of ALA (2 to 3 g per day) for the primary and secondary prevention of [[Coronary heart disease|CHD]]."<ref name="pmid15945135">{{cite journal |author=Mozaffarian D |title=Does α-linolenic acid intake reduce the risk of coronary heart disease? A review of the evidence |journal=Alternative therapies in health and medicine |volume=11 |issue=3 |pages=24–30; quiz 31, 79 |year=2005 |pmid=15945135 |doi=}}</ref>
==Drying oils==
{{see main|drying oil}}
ALA is the most abundant unsaturated component of several [[drying oil]]s (e.g. [[Perilla oil|perilla]], [[walnut]] and [[linseed oil]]s.)
==See also==
*[[Essential fatty acid]]
*[[List of omega-3 fatty acids|List of ''n''−3 fatty acids]]
*[[Essential nutrient]]
==References==
{{Reflist|2}}
{{Fatty acids}}
[[Category:Fatty acids|α]]
[[Category:Essential fatty acids]]
[[Category:Essential nutrients]]
[[da:Alfalinolensyre]]
[[de:Alpha-Linolensäure]]
[[es:Ácido alfa-linolénico]]
[[fr:Acide α-linolénique]]
[[lv:Linolēnskābe]]
[[nl:Alfa-linoleenzuur]]
[[ja:Α-リノレン酸]]
[[pl:Kwas linolenowy]]
[[pt:Ácido alfa-linolênico]]
[[ru:Линоленовая кислота]]
[[sv:Alfa-linolensyra]]