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Alpha-linolenic acid



α-Linolenic acid
Other names Linolenic acid; α-Linolenic acid; cis,cis,cis-9,12,15-Octadecatrienoic acid; (Z,Z,Z)-9,12,15-Octadecatrienoic acid; Industrene 120
Identifiers
CAS number 463-40-1
Properties
Molecular formula C18H30O2
Molar mass 278.43 g//mol
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Alpha-linolenic acid (ALA) is a an organic compound found in many common vegetable oils. Systematically, it is named all-cis-9,12,15-octadecatrienoic acid.[1] 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 omega end. Thus, ALA is both a polyunsaturated fatty acid, and an omega-3 fatty acid. It is an isomer of γ-linolenic acid, an omega-6 fatty acid.

Contents

Dietary sources

  Seed oils are the richest sources of alpha linolenic acid, notably those of rapeseed (canola), soybeans, walnuts, flaxseed (Linseed), perilla, chia and hemp. Alpha linolenic acid is also obtained from the thylakoid membranes of the green leaves of broadleaf plants (the membranes responsible for photosynthesis).[2] Greens, therefore, and animals that eat greens, are often a good source of ALA.

Common nameAlternate nameLinnaean name% ALA†ref.
Chia chia sageSalvia hispanica64% [3]
KiwiChinese gooseberryActinidia chinensis62%[3]
PerillashisoPerilla frutescens58%[3]
FlaxlinseedLinum usitatissimum55%[3]
LingonberrycowberryVaccinium vitis-idaea49%[3]
PurslaneportulacaPortulaca oleracea35%[3]
Sea Buckthorn seaberry Hippophae rhamnoides L.32%[4]
HempcannabisCannabis sativa20%[3]
RapeseedcanolaBrassica napus10%[1]
Soybean soyaGlycine max8%[1]
  †average val

Role in nutrition and health

Alpha-linolenic acid is a member of the group of essential fatty acids called omega-3 fatty acids, so called because they are an essential dietary requirement for all mammals. Most seeds and seed oils are much richer in the omega-6 fat linoleic acid. Linoleic acid is also an essential fat, but it, and the other omega-6 fats, compete with omega-3s for positions in cell membranes and have very different effects on human health. (See Essential fatty acid interactions.)

Eicosapentaenoic acid (EPA; 20:5n–3) and docosahexaenoic acid (DHA; 22:6n–3) play a vital role in many metabolic processes. Although these 2 fatty acids are readily available from fish, these marine-derived fatty acids can also be synthesized by humans from alpha-linolenic acid (ALA; 18:3n–3). 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.[citation needed] It is generally assumed that linoleic acid (LA; 18:2n–6) reduces EPA synthesis because of the competition between ALA and LA for common desaturation and elongation enzymes.

Studies have found evidence that ALA is related to a lower risk of cardiovascular disease.[5][6] However, the mechanism is still unclear: The body converts ALA into the longer chain fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and it is unknown whether the protective effect against cardiac arrhythmia is exerted by ALA itself, or by these metabolic products. Some studies have linked ALA with rapidly progressing prostate cancer[7] and macular degeneration,[8] 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 models of both global ischemia and KA-induced epilepsy.[9]

A large 2006 study found no association between total alpha-linolenic acid intake and overall risk of prostate cancer.[10]

Linolenic acid and trans fats

When partially hydrogenated, all unsaturated fatty acids form trans fats. Soybeans are the largest source of edible oils in the U.S., and 40% of soy oil production is partially hydrogenated.[11][12] The low oxidative stability of ALA is one reason that soybean oil undergoes partial hydrogenation. Regulations forcing the listing or banning of trans fats have spurred the development of low-linolenic soybeans. These yield a more stable oil requiring hydrogenation less often, and therefore providing trans-free alternatives into many applications such as frying oil.[13] Several consortia are bringing low-linolenic soy to market. DuPont's effort involves silencing the FAD2 gene that codes for Δ6-desaturase, giving a soy oil with very low levels of both α-linolenic and linoleic acids. [14]

In heart disease

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 CHD."[15]

Other uses—drying oils

See main article: drying oil

ALA is the most abundant unsaturated component of several drying oils (e.g. perilla, walnut and linseed oils.)

See also

References

  1. ^ a b c Beare-Rogers (2001). IUPAC Lexicon of Lipid Nutrition (pdf). Retrieved on 22 February, 2006.
  2. ^ Chapman, David J.; De-Felice, John and Barber, James (May 1983). "Growth Temperature Effects on Thylakoid Membrane Lipid and Protein Content of Pea Chloroplasts 1". Plant Physiol 72(1): 225–228. Retrieved on 2007-01-15.
  3. ^ a b c d e f g Seed Oil Fatty Acids - SOFA Database Retrieval
  4. ^ Li, Thomas S. C. (1999). "Sea buckthorn: New crop opportunity". Perspectives on new crops and new uses: 335-337, Alexandria, VA: ASHS Press. Retrieved on 2006-10-28. 
  5. ^ Penny M. Kris-Etherton, William S. Harris, [and] Lawrence J. Appel, for the Nutrition Committee (2002). "Fish Consumption, Fish Oil, Omega-3 Fatty Acids, and Cardiovascular Disease" (pdf). Circulation 106 (21): 2747-2757. doi:10.1161/01.CIR.0000038493.65177.94. Retrieved on 2006-07-25. PMID 12438303
  6. ^ William E. Connor (2000). "Importance of n-3 fatty acids in health and disease" (pdf). American Journal of Clinical Nutrition 71 (1 Suppl.): 171S-5S. Retrieved on 2006-07-25. PMID 10617967
  7. ^ Brouwer IA, Katan MB, Zock PL (2004). "Dietary alpha-linolenic acid is associated with reduced risk of fatal coronary heart disease, but increased prostate cancer risk: a meta-analysis.". Journal of Nutrition 134 (4): 919-22. Retrieved on 2006-11-13. PMID 15051847
  8. ^ Eunyoung Cho, Shirley Hung, Walter C Willett, Donna Spiegelman, Eric B Rimm, Johanna M Seddon, Graham A Colditz and Susan E Hankinson (2001). "Prospective study of dietary fat and the risk of age-related macular degeneration". American Journal of Clinical Nutrition 73 (2): 209-218. Retrieved on 2006-11-13. PMID 11157315
  9. ^ Inger Lauritzen, Nicolas Blondeau, Catherine Heurteaux, Catherine Widmann, Georges Romey and Michel Lazdunski (2000). "Polyunsaturated fatty acids are potent neuroprotectors". The EMBO Journal 19 (8): 1784-1793. Retrieved on 2005-10-06. PMID 10775263
  10. ^ Koralek DO, Peters U, Andriole G, et al (2006). "A prospective study of dietary alpha-linolenic acid and the risk of prostate cancer (United States)". Cancer Causes Control 17 (6): 783–91. doi:10.1007/s10552-006-0014-x. PMID 16783606. Retrieved on 2007-11-14.
  11. ^ Fitzgerald, Anne and Brasher, Philip. "Ban on trans fat could benefit Iowa". Truth About Trade and Technology. Retrieved on January 3, 2007.
  12. ^ Kinney, Tony. Metabolism in Plants to Produce Healthier Food Oils (slide #2). Retrieved on 2007-01-11.
  13. ^ Monsanto. ADM To Process Monsanto's VISTIVE™ Low Linolenic Soybeans At Indiana Facility. Retrieved on 2007-01-06.
  14. ^ Kinney, Tony. Metabolism in Plants to Produce Healthier Food Oils. Retrieved on 2007-01-11.
  15. ^ Mozaffarian D (2005). "Does alpha-linolenic acid intake reduce the risk of coronary heart disease? A review of the evidence". Alternative therapies in health and medicine 11 (3): 24–30; quiz 31, 79. PMID 15945135.
v • d • e
Lipids: fatty acids
SaturatedButyric - Hexanoic - Caprylic - Decanoic - Lauric - Myristic - Palmitic - Stearic - Arachidic - Behenic - Lignoceric
Omega-3 fatty acidAlpha-linolenic - Stearidonic acid - Eicosapentaenoic acid - Docosahexaenoic acid
Omega-6 fatty acidLinoleic - Gamma-Linolenic acid - Dihomo-gamma-linolenic acid - Arachidonic
Omega-9 fatty acidOleic - Erucic
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Alpha-linolenic_acid". A list of authors is available in Wikipedia.
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