Alpha-linolenic acid 153316 222025283 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|&nbsp; | 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]]