An unsaturated fatty acid, C17H31COOH, considered essential to the human diet, that is an important component of drying oils, such as linseed oil.
[Greek linon, flax + OLEIC ACID.]
linoleic acid
Dictionary:
lin·o·le·ic acid (lĭn'ə-lē'ĭk)  |
n.
An unsaturated fatty acid, C17H31COOH, considered essential to the human diet, that is an important component of drying oils, such as linseed oil.
An unsaturated fatty acid, C17H31COOH, considered essential to the human diet, that is an important component of drying oils, such as linseed oil.
| 5min Related Video: Linoleic acid |
| Chemistry Dictionary: linoleic acid |
A liquid polyunsaturated fatty acid with two double bonds, CH3(CH2)4CH:CHCH2CH:CH(CH2)7COOH. Linoleic acid is abundant in plant fats and oils, e.g. linseed oil, groundnut oil, and soya-bean oil. It is an essential fatty acid.
| Food and Nutrition: linoleic acid |
An essential polyunsaturated fatty acid (C18 : 2 ω6), predominant in most edible vegetable oils.
| Food and Fitness: linoleic acid |
An essential polyunsaturated fatty acid which must be obtained from food. It belongs to the family called omega-6 fatty acids, obtained in the diet principally from vegetable seeds and polyunsaturated margarines. Linoleic acid is the raw material for a number of compounds vital for health (e.g. arachidonic acid which is involved in the inflammation response). Linoleic acid is especially important for the proper growth and development of infants. It was once known as vitamin F but is no longer regarded as a vitamin.
| Dental Dictionary: linoleic acid |
n
An unsaturated fatty acid essential to nutrition. Linoleic acid occurs in many plant glycerides.
| Alternative Medicine Encyclopedia: Linoleic Acid |
Description
Linoleic acid is a colorless to straw-colored liquid polyunsaturated fatty acid (C18H32O2) of the omega-6 series. Linoleic and another fatty acid, gamma-linolenic, or gamolenic, produce compounds called prostaglandins. Prostaglandins are substances that are found in every cell, are needed for the body's overall health maintenance, and must be replenished constantly. Linoleic acid is an essential fatty acid, which means that the body cannot produce it, so it must be obtained in the diet.
Linoleic acid is an important fatty acid, especially for the growth and development of infants. Fatty acids help to maintain the health of cell membranes, improve nutrient use, and establish and control cellular metabolism. They also provide the raw materials that help in the control of blood pressure, blood clotting, inflammation, body temperature, and other body functions. Fatty acids are consumed in the greatest quantities in fat. Although many people are encouraged to consume less fat in their diets, fat is still an important component of a healthy body. Fat stores the body's extra calories, helps insulate the body, and protects body tissues. Fats are also an important energy source during exercise, when the body depends on its calories after using up available carbohydrates. Fat helps in the absorption, and transport through the bloodstream, of the fat-soluble vitamins A, D, E, and K.
Conjugated linoleic acid (CLA) is a naturally occurring mixture of various isomers of linoleic acid with conjugated double bonds. The isomers of CLA have different shapes, functions, and benefits. CLA supplements, or fats containing CLA, generally contain a mixture of these isomers. Although CLA is present in many foods and can be synthesized from linoleic acid, it is made naturally in the stomach, especially in ruminant animals. (Ruminants are animals that regurgitate food and chew it, known as "chewing the cud." Cows and sheep are ruminants.) For this reason, CLA is found primarily in dairy and beef products, as well as other foods derived from ruminant animals. Many people have likely decreased their intake of CLA for two reasons. First, beef and dairy fat are usually decreased or deleted from many diets. Second, many cattle are now fed grain diets, which are lower in linoleic acid than the grass on which they used to feed, so there is less CLA in beef and dairy foods. It is possible to increase the CLA in milk by adding a linoleic acid supplement to livestock feed. The supplement also increases lean tissue and decreases fat in the animals, and induces dairy cattle to produce more milk.
Linoleic acid is found in fish oil, meat, milk, and other dairy products. It is also a constituent of many vegetable oils, including evening primrose oil, sunflower oil, and safflower oil. Commercially produced linoleic acid is used in margarine, animal feeds, emulsifying agents, soaps, and drugs.
General Use
As mentioned, CLA supplements, or fats containing CLA, generally contain a mixture of CLA isomers. Plant oils, however, contain little CLA, but are a rich source of linoleic acid. While linoleic acid may be taken as a supplement to help with certain conditions, the supplement will not necessarily increase CLA levels in the body.
Anticarcinogenic
One particular isomer in CLA, known as cis-9, trans-11, is linked to anticancer benefits. Studies with animals have shown CLA to reduce breast, prostate, stomach, colorectal, lung, and skin cancers. The CLA may slow the growth of cells that give rise to cancer. A human study has shown an association between linoleic acids and a decreased risk for prostate cancer. In addition, a study done in 2001 on human breast cancer cells grown in a laboratory medium showed that linoleic acid works to reduce tumor size through its effects on a gene that controls the rate of apoptosis, or cell self-destruction.
Cystic Fibrosis
Infants with cystic fibrosis (CF) often have poor weight gain and growth and an inability to absorb fats. Some research suggests that infants with CF can benefit from formula with a high linoleic acid content because it optimizes nutrition, growth, and feeding efficiency.
Multiple Sclerosis
Multiple sclerosis (MS) is a disease in which demyelination, loss of myelin sheath material, occurs. (The myelin sheath is a fatty substance that surrounds and insulates the axon of some nerve cells.) This leads to disruptions in nerve impulse transmission. Linoleic acid is believed to be helpful because myelin is composed of lecithin, which is made of linoleic and other fatty acids. Many diets recommended for MS patients include supplements. Patients supplementing with linoleic acid show a smaller increase in disability and reduced severity and duration of attacks than those with no linoleic acid supplement. Evening primrose oil is beneficial because of its specialized fatty-acid content, including linoleic acid. Doses of sunflower seed oil or evening primrose oil to provide 17 grams linoleic acid per day may be beneficial.
Pregnancy
One study indicated that low doses of linoleic acid and calcium can reduce the incidence of preeclampsia in high-risk women. (Preeclampsia is the development of hypertension with increased protein in the urine or accumulation of watery fluid in cells or tissues or both, due to pregnancy.) Another study showed, however, that linoleic acid consumption can have a negative effect on fetal growth. Pregnant women should talk to their doctors before taking linoleic acid or any other supplement.
Diet and Nutrition
CLA helps regulate how the body accumulates and retains fat. It has been shown to reduce body fat, improve muscle tone, improve nutrient usage, and reduce the appetite by improving the way the body extracts energy from less food. These properties are useful not only for those trying to lose weight or tone muscles, but also for people with nutrient absorption disorders and other digestive problems. The CLA isomer linked with reducing body fat and increasing lean muscle mass is trans-10, cis-12.
Skin Care
Linoleic acid helps relieve flaky, itchy, or rough skin and maintain smooth, moist skin. A tablespoon of linoleic acid-rich foods or oils may be added on a daily basis to help improve and moisturize skin. Linoleic acid may also help with skin disorders such as atopic eczema. Evening primrose oil is taken to help with skin, hair, and nail repair.
Other Uses
Animal research suggests that CLA supplementation may limit food allergy reactions and improve glucose tolerance. It is also used as a nutritional supplement for allergic respiratory disease, circulation, arthritis, and inflammatory problems. CLA is also a potent antioxidant and may help reduce plaque formation in arteries and thus help prevent heart disease. Evening primrose oil helps to reduce arthritis pain and depression. It also helps to control diabetes, liver and kidney damage due to alcohol, and several symptoms of premenstrual syndrome (PMS).
Linoleic acid appears to have at least one negative effect on the human body, however. It appears to increase a person's risk of developing age-related macular degeneration (ARMD), a disease of the eye that leads to a progressive loss of vision and eventual blindness.
Preparations
Evening primrose oil is a fixed oil obtained from the seeds of Oenothera biennis or other spp. (Onagraceae). It contains about 72% linoleic acid and 9% gamolenic acid. Typical doses expressed as gamolenic acid are 320 or 480 mg daily, taken in two or three doses. Safflower oil is the refined fixed oil obtained from the seeds of the safflower, or false (bastard) saffron, Carthamus tinctorius (Compositae). It contains about 75% linoleic acid as well as various saturated fatty acids.
CLA is available in beef and dairy products, but to avoid eating too many fatty animal foods, supplements may be taken. CLA comes in capsules and softgels that range in potency from 600 to 1,000 mg. A specialist should be consulted to determine what is most appropriate.
Precautions
CLA appears to be safe and nontoxic at supplemental levels. However, using evening primrose oil as a supplement for linoleic acid can cause symptoms of undiagnosed temporal lobe epilepsy and should be used with caution in patients with a history of epilepsy.
Side Effects
CLA may cause gastrointestinal upset in isolated cases, and evening primrose oil can cause minor gastrointestinal upset and headache.
Interactions
People who take epileptogenic drugs (drugs which cause epilepsy), in particular phenothiazines, may have interactions with evening primrose oil, and should talk to their doctors before using a supplement.
Resources
Books
Dox, Ida G., B. John Melloni, and Gilbert M. Eisner. The Harper Collins Illustrated Medical Dictionary. New York: HarperPerennial, 1993.
Periodicals
"Harvard Study Outlines Role of Fats in Blinding Eye Disease." Angiogenesis Weekly (October 12, 2001).
Herbel, Barbara K., Michelle K. McGuire, Mark A. McGuire, and Terry D. Shultz. "Safflower Oil Consumption Does Not Increase Plasma Conjugated Linoleic Acid Concentrations in Humans." American Journal of Clinical Nutrition 67 (1998): 332–7.
Majumder, Barun, Klaus J. Wahle, Susan Moir, and Steven D. Heys. "Conjugated Linoleic Acid Reduces Breast Tumor Growth Both by P53-dependent and P53-independent Pathways." Journal of Nutrition 131 (November 2001): 3140S.
Van Egmond, Andreas W.A., Michael R. Kosorok, Rebecca Koscik, Anita Laxova, and Philip M. Farrell. "Effect of Linoleic Acid Intake on Growth of Infants with Cystic Fibrosis." American Journal of Clinical Nutrition 63 (1996): 746–52.
[Article by: Melissa C. McDade; Rebecca J. Frey, PhD]
| Sports Science and Medicine: linoleic acid |
A yellow oily polyunsaturated fatty acid. Linoleic acid is an essential fatty acid. It is a component of lecithin and may be used to synthesize arachidonic acid and linolenic acid. It was once known as vitamin F, but is no longer regarded as a vitamin.
| Veterinary Dictionary: linoleic acid |
An essential fatty acid; contains 18 carbons and 2 double bonds at carbons 9, 10 and 12,13; precursor of n-6 or omega 6 fatty acids; the major unsaturated fatty acid found in vegetable oils.
- l. acid deficiency — dry, scaling skin and alopecia have been reported in cats deficient in linoleic acid. Dietary deficiency occurs in cats fed diets low in fat, containing rancid fat, or with little or no animal-source fats.
| Wikipedia: Linoleic acid |
Not to be confused with linolenic acid.
| Linoleic acid | |
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| IUPAC name |
cis, cis-9,12-octadecadienoic acid.[1]
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| Identifiers | |
| CAS number | 60-33-3  |
| SMILES |
CCCCC/C=C\C/C=C\CCCCCCCC(=O)O
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| Properties | |
| Molecular formula | C18H32O2 |
| Molar mass | 280.45 g mol−1 |
| Density | 0.9 g/cm3 |
| Melting point |
-5 °C |
| Boiling point |
229°C |
| Solubility in methanol | methanol 3.22 M [2] |
| (what is this?) (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Linoleic acid (LA) is an unsaturated omega-6 fatty acid. It is a colorless liquid. In physiological literature, it is called 18:2(n-6). Chemically, linoleic acid is a carboxylic acid with an 18-carbon chain and two cis double bonds; the first double bond is located at the sixth carbon from the omega end.
The word linoleic comes from the Greek word linon (flax). Oleic means of, relating to, or derived from oil or olive or of or relating to oleic acid since removing the omega-6 double bond produces oleic acid.
Contents |
In Physiology
Linoleic acid (LA) is a polyunsaturated fatty acid used in the biosynthesis of arachidonic acid (AA) and thus some prostaglandins. It is found in the lipids of cell membranes. It is abundant in many vegetable oils, especially safflower and sunflower oils.
Linoleic acid is a member of the group of essential fatty acids called omega-6 fatty acids, so called because they are an essential dietary requirement for all mammals. The other group of essential fatty acids is the omega-3 fatty acids, for example Alpha-linolenic acid. Omega-6 deficiency symptoms include dry hair, hair loss,[3] and poor wound healing.[4]
Metabolism and Eicosanoids
The first step in the metabolism of Linoleic Acid (LA) is performed by Δ-6-desaturase, which converts LA into gamma-Linolenic acid (GLA).
There is evidence suggesting that infants lack Δ-6-desaturase of their own, and must acquire it through breast milk. Studies show that breast-milk fed babies have higher concentrations of GLA than formula-fed babies, while formula-fed babies have elevated concentrations of LA. [5]
GLA is converted to Dihomo-gamma-linolenic acid (DGLA), which in turn is converted to Arachidonic acid (AA). One of the possible fates of AA is to be transformed into a group of metabolites called eicosanoids, a class of paracrine hormones. The three types of eicosanoids are prostaglandins, thromboxanes, and leukotrienes. Eicosanoids are only produced from AA and tend to be pro-inflammatory. [6] For example, both Thrombaxane and LeukotrieneB4 are proaggretory and vasoconstrictive eicosanoids. Another important clinical effect is that the oxidized metabolic products of linolenic acid such as 9--hydroxyoctadecanoic acid and 13-hydroxyoctadecanoic acid have also been shown to activate TRPV1, the capsaicin receptor and through this might play a major role in hyperalgesia and allodynia.[7]
An increased intake of Omega 3 fatty acids with a decrease in Omega 6 fatty acids has been shown to attenuate inflammation due to reduced production of these eicosanoids.[8]
One study monitoring two groups of survivors of myocardial infarction concluded that “the concentration of alpha-linolenic acid was increased by 68%, in the experimental group, and that of linoleic acid reduced by 7%...the survivors of a first myocardial infarction, assigned to a Mediterranean alpha-linolenic acid rich diet, had a markedly reduced rate of recurrence, other cardiac events and overall mortality.” [9]
Possible Roles in Disease
Cancer Prevention
A study in mice has shown that dietary intake of Conjugated Linoleic Acid (CLA) can help prevent cancer in mice. The study looked at a specific isomer of LA and studied its effect on cancer induced by dimethylbenz(a)anthracene. The study suggested a significant effect of CLA intake on the reduction of carcinogenesis. [10]
Cystic fibrosis
Since children with cystic fibrosis suffer from Essential Fatty Acid Deficiency due to malabsorption, it was hypothesized that high doses of LA might aid in their growth. The study looked at two groups of infants with cystic fibrosis on diets with two different levels of LA. It was shown that supplementary LA, indeed, has a positive effect on the growth of infants with cystic fibrosis, especially between 6 and 9 months of age.[11]
Dermatitis
Dermatitis is one of the first signs of an Essential Fatty Acid deficiency in both humans and animals. Until 1955, one of the most widely applied treatments for atopic eczema was a high dose of GLA. [12]
Diabetes
A number of studies have shown that diabetics require higher than normal intakes of LA. Because diabetics have consistently been shown to have above normal levels of LA while having lower than normal levels of GLA, it is believed that diabetics have impaired Δ-6-desaturase activity. Increased intakes of LA have been shown to attenuate diabetic complications in numerous studies.[13]
Industrial uses
Linoleic acid is used in making soaps, emulsifiers, and quick-drying oils. Reduction of linoleic acid yields linoleyl alcohol. Linoleic acid has become increasingly popular in the beauty products industry because of its beneficial properties on the skin. Research points to linoleic acid's anti-inflammatory, acne reductive, and moisture retentive properties when applied topically on the skin.[14][15][16]
Dietary Sources
| Name | % LA† | ref. |
|---|---|---|
| Safflower Oil | 78% | |
| Grape Seed Oil | 73% | |
| Poppy Seed Oil | 70% | |
| Sunflower Oil | 68% | |
| Hemp Oil | 60% | |
| Corn Oil | 59% | |
| Wheat Germ Oil | 55% | |
| Cottonseed Oil | 54% | |
| Soybean Oil | 51% | |
| Walnut Oil | 51% | |
| Peanut Oil | 48% | |
| Sesame Oil | 45% | |
| Rice Bran Oil | 39% | |
| Pistachio Oil | 32.7% | |
| Canola Oil | 21% | |
| Egg Yolk | 16% | |
| Linseed oil | 15% | |
| Lard | 10% | |
| Olive Oil | 10% | |
| Palm Oil | 10% | |
| Cocoa Butter | 3% | |
| Macadamia Oil | 2% | |
| Butter | 2% | |
| Coconut Oil | 2% | |
| †average val | ||
See also
- alpha-Linolenic acid
- Conjugated linoleic acid
- Essential fatty acids
- Essential fatty acid interactions
- Eicosanoids
- Essential nutrients
- Linolein
References
- ^ Beare-Rogers (2001). "IUPAC Lexicon of Lipid Nutrition" (pdf). http://www.iupac.org/publications/pac/2001/pdf/7304x0685.pdf. Retrieved 2006-02-22.
- ^ Solubility of linoleic acid in methanol
- ^ Cunnane S, Anderson M (01 Apr 1997). "Pure linoleate deficiency in the rat: influence on growth, accumulation of n-6 polyunsaturates, and (1-14C) linoleate oxidation". J Lipid Res 38 (4): 805–12. PMID 9144095. http://www.jlr.org/cgi/reprint/38/4/805. Retrieved 2007-01-15.
- ^ Ruthig DJ & Meckling-Gill KA. (01 Oct 1999). "Both (n-3) and (n-6) fatty acids stimulate wound healing in the rat intestinal epithelial cell line, IEC-6". Journal of Nutrition 129 (10): 1791–8. PMID 10498749. http://jn.nutrition.org/cgi/content/full/129/10/1791. Retrieved 2007-01-15.
- ^ David F. Horrobin (1993).“Fatty acid metabolism in health and disease: the role of Δ-6-desaturase.” American Journal of Clinical Nutrition. 57: 732S-7S.
- ^ Piomelli, Daniele (2000). "Arachidonic Acid". Neuropsychopharmacology: The Fifth Generation of Progress. http://www.acnp.org/g4/GN401000059/Default.htm. Retrieved on 4/16/09.
- ^ Patwardhan AM, Scotland PE, Akopian AN, Hargreaves KM. (2009). Activation of TRPV1 in the spinal cord by oxidized linoleic acid metabolites contributes to inflammatory hyperalgesia. Proc Natl Acad Sci U S A. 2009 Nov 3;106(44):18820-4. PMID 19843694
- ^ John E. Kinsella, Belur Lokesh, and Richard A. Stone (1990) “Dietary n-3 polyunsatruated fatty acids and amelioration of cardiovascular disease: possible mechanisms.” American Journal of Clinical Nutrition. 52: 1-28.
- ^ Michel de Lorgeril, and Serge Renaud (6/11/94). “Mediterranean alpha-linolenic acid-rich diet in secondary prevention of coronary heart disease.” Lancet 343: 8911.
- ^ Mammary Cancer Prevention by Conjugated Dienoic Derivative of Linoleic Acid Cancer Research 51, 6118-6124, November 15, 1991
- ^ Effect of linoleic acid intake on growth of infants with cystic fibrosis, The American Journal of Clinical Nutrition, 1996, vol. 63, no5, pp. 746-752.
- ^ David F. Horrobin (1993).“Fatty acid metabolism in health and disease: the role of Δ-6-desaturase.” American Journal of Clinical Nutrition. 57: 732S-7S.
- ^ David F. Horrobin (1993).“Fatty acid metabolism in health and disease: the role of Δ-6-desaturase.” American Journal of Clinical Nutrition. 57: 732S-7S.
- ^ "Plant oils: Topical application and anti-inflammatory effects (croton oil test)". Dermatol. Monatsschr 179: 173. 1993.
- ^ Letawe,; Letawe C, Boone M, Pierard GE (March 1998). "Digital image analysis of the effect of topically applied linoleic acid on acne microcomedones". Clinical & Experimental Dermatology 23 (2): 56–58. doi:. PMID 9692305 : 9692305. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=9692305&itool=iconabstr&query_hl=17&itool=pubmed_docsum.
- ^ Darmstadt, G L; Darmstadt GL, Mao-Qiang M, Chi E, Saha SK, Ziboh VA, Black RE, Santosham M, Elias PM (2002). "Impact of topical oils on the skin barrier: possible implications for neonatal health in developing countries". Acta Paediatrica 91 (5): 546–554. doi:.
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Mentioned in
- palmitolic
- safflower oil (materials)
- arachis oil
- essential fatty acid
- safflower meal
- linoxin
- linseed oil
- polyunsaturated acid (organic chemistry)
- cotton oil (materials)
- Omega-6 Fatty Acids
