Trans fat

Trans fats occur naturally in the fats of products made from ruminant animals, such as cheese or butter. Some trans fats are the result of food processing, especially when applied to cooking oils and margarine.

Image:Trans-vaccenic acid.svg

Trans fats occur in meat and dairy products from ruminants. For example, butter contains about 3% trans fat by weight.{{Cite web |date=2019-04-01 |title=Butter, salted |url=https://fdc.nal.usda.gov/fdc-app.html#/food-details/173410/nutrients |access-date=2024-10-11 |website=FoodData Central}} These naturally occurring trans fats include conjugated linoleic acid (CLA) and vaccenic acid. They arise from the action of bacteria in the rumen. Polyunsaturated fats are toxic to the rumen-based bacteria, which detoxify the fats by changing some cis-double bonds to trans-double bonds. In contrast to industrially produced trans fats, this bacterial process produces only a few specific isomers. As industrial sources of trans fats are eliminated, increased attention focuses on ruminant derived trans fats.{{cite journal |doi=10.1002/lipd.12324|title=Trans-10 18:1 in ruminant meats: A review |year=2021 |last1=Alves |first1=Susana P. |last2=Vahmani |first2=Payam |last3=Mapiye |first3=Cletos |last4=McAllister |first4=Tim A. |last5=Bessa |first5=Rui J. B. |last6=Dugan |first6=Michael E. R. |journal=Lipids |volume=32 |issue=6 |pages=539–562 |pmid=34608647 |s2cid=238356805 }}

Small amounts of trans fats occur in meat and milk fat.

{{main|Fat hydrogenation}}

Trans fat can be an unintentional byproduct of the industrial processing of oils. Unlike naturally derived trans fats, the trans fats that result from hydrogenation consist of many isomers. In food production, liquid cis-unsaturated fats such as vegetable oils are hydrogenated to produce more saturated fats, which have desirable properties:

• The shelf life of fats correlates with the degree of saturation: polyunsaturated fats are prone to autoxidation whereas saturated fats, being virtually inert in air, have very long shelf lives.
• Saturated fats tend to be more solid at room temperature. This property is important for margarine, one of the original uses for fat hydrogenation.

However, an isomerization side reaction during fat hydrogenation can convert remaining unsaturated fats to the thermodynamically-favored trans isomer.

File:FatHydrogenation.svg

A number of old and new ingredients are available to replace partially-hydrogenated oil containing significant levels of trans fat. These include partially-hydrogenated oil made with improved processes, plant oils rich in monounsaturated fats and saturated fats, and a mix of fats combined with interesterification.{{cite journal | last1 = Teresa Tarrago-Trani | first1 = Maria | last2 = Phillips | first2 = Katherine M. | last3 = Lemar | first3 = Linda E. | last4 = Holden | first4 = Joanne M. | year = 2006 | title = New and Existing Oils and Fats Used in Products with Reduced Trans-Fatty Acid Content | url = https://www.ars.usda.gov/ARSUserFiles/80400525/Articles/JADA106_867-880.pdf| journal = Journal of the American Dietetic Association | volume = 106 | issue = 6| pages = 867–880 | doi = 10.1016/j.jada.2006.03.010 | pmid = 16720128 }} The technology has improved such that a 2021 review indicates that trans fat from hydrogenated fats is no longer a problem in modern countries.

When heated (cooked), some unsaturated fats change from their normal geometry to trans. The rate of isomerization is accelerated by free radicals.{{cite web |title=About Trans Fat and Partially Hydrogenated Oils |url=https://www.cspinet.org/sites/default/files/media/documents/resource/trans_q_a.pdf |publisher=Center for Science in the Public Interest}}{{cite web|url=https://www.federalregister.gov/articles/2013/11/08/2013-26854/tentative-determination-regarding-partially-hydrogenated-oils-request-for-comments-and-for |title=Tentative Determination Regarding Partially Hydrogenated Oils |publisher=Federal Register |date=8 November 2013 |access-date=8 November 2013 |id=2013-26854, Vol. 78, No. 217 |archive-url=https://web.archive.org/web/20140406185048/https://www.federalregister.gov/articles/2013/11/08/2013-26854/tentative-determination-regarding-partially-hydrogenated-oils-request-for-comments-and-for |archive-date=6 April 2014 |url-status=live }}

There were suggestions in the scientific literature as early as 1956 that trans fats could cause an increase in coronary artery disease.{{cite journal|vauthors=Ascherio A, Stampfer MJ, Willett WC |title=Trans fatty acids and coronary heart disease|journal=The New England Journal of Medicine|year=1999|volume=340|issue=25|pages=1994–1998|doi=10.1056/NEJM199906243402511|pmid=10379026|url=https://www.hsph.harvard.edu/reviews/transfats.html|access-date=14 September 2006|archive-url=https://web.archive.org/web/20060903061226/http://www.hsph.harvard.edu/reviews/transfats.html|archive-date=3 September 2006}} Studies in the early 1990s brought renewed scrutiny and confirmation of the negative health impact of trans fats. In 1994, it was estimated that trans fats caused at least 20,000 deaths annually in the U.S. from heart disease.{{cite journal | vauthors = Willett WC, Ascherio A | title = Trans fatty acids: are the effects only marginal? | journal = American Journal of Public Health | volume = 84 | issue = 5 | pages = 722–4 | date = May 1994 | pmid = 8179036 | pmc = 1615057 | doi = 10.2105/AJPH.84.5.722 }} In the 1990s, activists such as the Center for Science in the Public Interest(CSPI) that had promoted trans fat safety began arguing that trans fats should be disclosed on product labels and menus.{{refn|References:

• {{cite web | author=Centre for Science in the Public Interest | title=Health Advocates Tell Top Restaurants 'Get an Oil Change' | url=https://www.cspinet.org/new/oilchange.html | date=1999 | access-date=22 July 2023}}
• {{cite magazine |last=Jacobson |first= Michael F |date=2004 |issue=31 |title=Good riddance to Trans! |magazine=Nutrition Action Healthletter |publisher=Center for Science in the Public Interest}} Cited in.{{cite journal | vauthors = Schleifer D | title = The perfect solution: How trans fats became the healthy replacement for saturated fats | journal = Technology and Culture | volume = 53 | issue = 1 | pages = 94–119 | date = January 2012 | doi = 10.1353/tech.2012.0018 | jstor = 41475458 | pmid = 22530389 | s2cid = 26343964 }}
• {{cite web | author=Centre for Science in the Public Interest | title=Artificial Trans Fat: A Timeline | url= https://www.cspinet.org/resource/artificial-trans-fat-timeline | date=2018 | access-date=22 July 2023}}}} Several lawsuits were launched against high-visibility restaurants and food manufacturers with the objective of supporting a broader phase-out of trans fats.{{cite news|url=http://edition.cnn.com/2003/LAW/05/14/oreo.suit/|title=Lawsuit dropped as Oreo looks to drop the fat|publisher=CNN|date=14 May 2003|access-date=14 July 2011}}{{cite web|url=https://www.cspinet.org/news/cspi-withdraws-lawsuit-after-kfc-cuts-trans-fat-20061030|title= CSPI withdraws from lawsuit after KFC cuts trans fat|publisher=Centre for Science in the Public Interest|date=2006|access-date=22 July 2023}}

Mandatory food labeling was introduced in several countries{{cite journal| title=Approaches to removing trans fats from the food supply in industrialized and developing countries|journal=European Journal of Clinical Nutrition|volume=63|pages=S50–7|year=2009|doi=10.1038/ejcn.2009.14|issue=Suppl 1| vauthors = L'Abbé MR, Stender S, Skeaff CM, Tavella M |url=http://sedici.unlp.edu.ar/handle/10915/82697|doi-access=free|pmid=19190645 |pmc=2830089}} and Denmark was first to mandate limits on industrially-produced trans fats in 2004.{{cite web|url=https://www.who.int/publications/i/item/9789240021105|title=Information Sheet: REPLACE trans fat: an action package to eliminate industrially produced trans-fatty acids |publisher=World Health Organization|date=2021|access-date=22 July 2023}} In January 2007, faced with the prospect of an outright ban on the sale of their product, Crisco was reformulated to meet the U.S. Food and Drug Administration (FDA) definition of "zero grams trans fats per serving" (that is less than one gram per tablespoon, or up to 7% by weight; or less than 0.5 grams per serving size)Regulation: 21 CFR 101.9 (c)(2)(ii). {{cite web|last=Food and Drug Administration|title=21 CFR Part 101. Food labeling; trans fatty acids in nutrition labeling; consumer research to consider nutrient content and health claims and possible footnote or disclosure statements; final rule and proposed rule|publisher=National Archives and Records Administration|date=11 July 2003|url=http://www.cfsan.fda.gov/~acrobat/fr03711a.pdf|access-date=18 January 2007|archive-url=https://web.archive.org/web/20070103035701/http://www.cfsan.fda.gov/~acrobat/fr03711a.pdf|archive-date=3 January 2007}}{{cite web| title=FDA acts to provide better information to consumers on trans fats|website=Food and Drug Administration|url=https://www.fda.gov/oc/initiatives/transfat/|access-date=26 July 2005|archive-url=https://web.archive.org/web/20050625032556/https://www.fda.gov/oc/initiatives/transfat/|archive-date=25 June 2005}}{{cite web|url=https://www.newswise.com/articles/view/541842/|title=Newswise: most consumers misinterpret meaning of trans fat information on Nutrition Facts panel|access-date=19 June 2008}}{{cite news |last=Shockman |first=Luke |title=Trans fat: 'Zero' foods add up |newspaper=Toledo Blade |date=5 December 2005 |url=http://toledoblade.com/apps/pbcs.dll/article?AID=/20051205/NEWS32/512030320 |access-date=18 January 2007 |archive-url=https://web.archive.org/web/20090621150507/http://toledoblade.com/apps/pbcs.dll/article?AID=%2F20051205%2FNEWS32%2F512030320 |archive-date=21 June 2009 }} by boosting the saturation and then diluting the resulting solid fat with unsaturated vegetable oils. Noting that elimination of industrially produced trans fat is feasible and achievable, the World Health Organization (WHO) has set a goal to make the world free from industrially produced trans fat by the end of 2023. By the end of 2021, the WHO announced that 40 countries had implemented industrial trans fat elimination policies that "are protecting 1.4 billion people from this deadly food compound" but that 10 of the 15 countries suffering the highest health impacts from trans fats had not yet adopted a policy.

A fatty acid is characterized as either saturated or unsaturated based on the respective absence or presence of C=C double bonds in its backbone. If the molecule contains no double C=C bonds, it is said to be saturated; otherwise, it is unsaturated to some degree.{{cite book|title=Food lipids: chemistry, nutrition, and biotechnology|pages=1–2|isbn=978-0-8247-0749-1|editor1=Casimir C. Akoh |editor2=David B. Min.|year=2002|publisher=M. Dekker|location=New York}}{{cite book|chapter-url=http://goldbook.iupac.org/F02330.html|chapter="fatty acid"|title=IUPAC Gold book|year=2014 |publisher=International Union of Pure and Applied Chemistry|doi=10.1351/goldbook.F02330 }}

The C=C double bond is rotationally rigid. If the hydrogen bonded to each of the carbons in this double bond are on the same side, this is called cis, and leads to a bent molecular chain. If the two hydrogens are on opposite sides, this is called trans, and leads to a straight chain.

Because trans fats are more linear, they crystallize more easily, allowing them to be solid (rather than liquid) at room temperatures. This has several processing and storage advantages.

In nature, unsaturated fatty acids generally have cis configurations as opposed to trans configurations.{{cite journal |vauthors=Martin CA, Milinsk MC, Visentainer JV, Matsushita M, de-Souza NE |date=June 2007 |title=Trans fatty acid-forming processes in foods: a review |journal=Anais da Academia Brasileira de Ciências |volume=79 |issue=2 |pages=343–50 |doi=10.1590/S0001-37652007000200015 |pmid=17625687 |doi-access=free}} Saturated fatty acids (those without any carbon-carbon double bonds) are abundant (see tallow), but they also can be generated from unsaturated fats by the process of fat hydrogenation. In the course of hydrogenation, some cis double bonds convert into trans double bonds. Chemists call this conversion an isomerization reaction.Udo Erasmus; Fats that heal, Fats that Kill, Alive books, 1993 edition, Pages 13-19.

Any molecule with a C=C double bond can be either a trans or a cis fatty acid depending on the configuration of the double bond. For example, oleic acid and elaidic acid are both unsaturated fatty acids with the chemical formula C₉H₁₇C₉H₁₇O₂. They both have a double bond located midway along the carbon chain. It is the geometry of this bond that sets oleic and elaidic acids apart. They have distinct physical-chemical properties of the molecule. For example, the melting point of elaidic acid is 45 °C higher than that of oleic acid.{{cite book|title=Handbook of chemistry and physics|url=http://www.hbcpnetbase.com|access-date=19 November 2007|edition=88th|series=2007–2008|year=2007|publisher=Taylor and Francis|chapter=Section 7: Biochemistry|chapter-url=http://www.hbcpnetbase.com/articles/07_05_86.pdf|archive-date=24 July 2017|archive-url=https://web.archive.org/web/20170724011402/http://www.hbcpnetbase.com/}} This notably means that it is a solid at human body temperatures.

{{main|Fat hydrogenation}}

The hydrogenation process was widely adopted by the food industry in the early 1900s; first for the production of margarine, a replacement for butter and shortening,{{cite encyclopedia | last1=Gormley | first1=James J. | last2=Juturu | first2=Vijaya | chapter=Partially Hydrogenated Fats in the US Diet and Their Role in Disease | encyclopedia=Modern Dietary Fat Intakes in Disease Promotion | date=2010 | publisher=Humana Press | veditors = De Meester F, Zibadi S, Watson RR | location=Totowa, NJ | isbn=978-1-60327-571-2 | series=Nutrition and Health | pages=85–94 | language=en | doi=10.1007/978-1-60327-571-2_5 }} and eventually for various other fats used in snack food, packaged baked goods, and deep fried products.

Full hydrogenation of a fat or oil produces a fully saturated fat. For food purposes, hydrogenation generally is not allowed to go to completion. The main target is a specific melting point and hardness, and this fine-tuning requires that some unsaturation (C=C bonds) remain. This partial hydrogenation turns some of the cis double bonds into trans bonds by an isomerization reaction.{{cite book | last1=Hill | first1=John W. | last2=Kolb | first2=Doris K | name-list-style = vanc | isbn=978-0-13-605449-8 | title=Chemistry for changing times | publisher=Pearson / Prentice Hall | year=2007}} This side reaction accounts for most of the trans fatty acids consumed today, by far.{{cite book | last1=Ashok | first1=Chauhan | last2=Ajit | first2=Varma | name-list-style = vanc | date=2009 | page = 181 | chapter=Chapter 4: Fatty acids | title=A Textbook of Molecular Biotechnology | publisher=I. K. International Pvt | isbn=978-93-80026-37-4}}

The standard 140 kPa (20 psi) process of hydrogenation produces a product of about 40% trans fatty acid by weight, compared to about 17% using higher pressures of hydrogen. Blended with unhydrogenated liquid soybean oil, the high-pressure-processed oil produced margarine containing 5 to 6% trans fat. Based on current U.S. labeling requirements (see below), the manufacturer could claim the product was free of trans fat.{{cite journal | vauthors = Eller FJ, List GR, Teel JA, Steidley KR, Adlof RO | title = Preparation of spread oils meeting U.S. Food and Drug Administration Labeling requirements for trans fatty acids via pressure-controlled hydrogenation | journal = Journal of Agricultural and Food Chemistry | volume = 53 | issue = 15 | pages = 5982–4 | date = July 2005 | pmid = 16028984 | doi = 10.1021/jf047849+ | bibcode = 2005JAFC...53.5982E }} The level of trans fat may also be altered by modification of the temperature and the length of time during hydrogenation.

The trans fat levels can be quantified using various forms of chromatography.{{cite journal |doi=10.1021/cr4002287|title=Lipid Geometrical Isomerism: From Chemistry to Biology and Diagnostics |year=2014 |last1=Chatgilialoglu |first1=Chryssostomos |last2=Ferreri |first2=Carla |last3=Melchiorre |first3=Michele |last4=Sansone |first4=Anna |last5=Torreggiani |first5=Armida |journal=Chemical Reviews |volume=114 |issue=1 |pages=255–284 |pmid=24050531 |doi-access=free }}

Trans fatty acids (TFAs) occur in small amounts in meat and milk of ruminants (such as cattle and sheep),{{cite journal | vauthors = Kuhnt K, Baehr M, Rohrer C, Jahreis G | title = Trans fatty acid isomers and the trans-9/trans-11 index in fat containing foods | journal = European Journal of Lipid Science and Technology | volume = 113 | issue = 10 | pages = 1281–1292 | date = October 2011 | pmid = 22164125 | pmc = 3229980 | doi = 10.1002/ejlt.201100037 }}{{cite book|first1=Fred August |last1=Kummerow |first2=Jean M. |last2=Kummerow|title=Cholesterol Won't Kill You, But Trans Fat Could|publisher=Trafford|year=2008|isbn=978-1-4251-3808-0}} typically 2–5% of total fat.{{cite book|isbn=0-662-43689-X|author=Trans Fat Task Force|title=TRANSforming the Food Supply|date=June 2006|publisher=Trans Fat Task Force |url=http://www.hc-sc.gc.ca/fn-an/nutrition/gras-trans-fats/tf-ge/tf-gt_rep-rap_e.html|access-date=7 January 2007}} Natural TFAs, which include conjugated linoleic acid (CLA) and vaccenic acid, originate in the rumen of these animals. CLA has two double bonds, one in the cis configuration and one in trans, which makes it simultaneously a cis- and a trans-fatty acid.{{Cite web|url=https://mejorandomishabitos.es/dieta-detox/|title=DIETA DETOX ✅ QUÉ ES Y SUS 13 PODEROSOS BENEFICIOS|date=October 24, 2019}}

A type of trans fat occurs naturally in the milk and body fat of ruminants (such as cattle and sheep) at a level of 2–5% of total fat.{{cite book|isbn=0-662-43689-X|author=Trans Fat Task Force|title=TRANSforming the Food Supply|date=June 2006|publisher=Trans Fat Task Force |url=https://www.canada.ca/en/health-canada/services/nutrients/fats/task-force-trans-fat/transforming-food-supply-report.html|access-date=7 January 2007}}

The US National Dairy Council has asserted that the trans fats present in foods of animal origin are of a different type than those in partially hydrogenated oils, and do not appear to exhibit the same negative effects.{{cite web| author=National Dairy Council|title=comments on 'Docket No. 2003N-0076 Food Labeling: Trans Fatty Acids in Nutrition Labeling'|website=Food and Drug Administration |date=18 June 2004|url=https://www.fda.gov/ohrms/dockets/dailys/04/June04/062304/03N-0076-emc00228-01.pdf|access-date=7 January 2007}} A scientific review agrees with the conclusion (stating that "the sum of the current evidence suggests that the Public health implications of consuming trans fats from ruminant products are relatively limited") but cautions that this may be due to the low consumption of trans fats from animal sources compared to artificial ones.

Despite this concern, the NAS dietary recommendations have not included eliminating trans fat from the diet. This is because trans fat is naturally present in many animal foods in trace quantities, and thus its removal from ordinary diets might introduce undesirable side effects and nutritional imbalances if proper nutritional planning is not undertaken. The NAS has, thus, "recommended that trans fatty acid consumption be as low as possible while consuming a nutritionally adequate diet".{{cite book|last=Food and nutrition board, institute of medicine of the national academies|title=Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients)|publisher=National Academies Press|year=2005|page = 424|url=http://darwin.nap.edu/books/0309085373/html/424.html}}{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes}} Like the NAS, the World Health Organization has tried to balance public health goals with a practical level of trans fat consumption, recommending in 2003 that trans fats be limited to less than 1% of overall energy intake.

A meta-analysis showed that all trans fats, regardless of natural or artificial origin equally raise LDL and lower HDL levels. Other studies though have shown different results when it comes to animal based trans fats like conjugated linoleic acid (CLA). Although CLA is known for its anticancer properties, researchers have also found that the cis-9, trans-11 form of CLA can reduce the risk for cardiovascular disease and help fight inflammation.{{cite journal | vauthors = Tricon S, Burdge GC, Kew S, Banerjee T, Russell JJ, Jones EL, Grimble RF, Williams CM, Yaqoob P, Calder PC | display-authors = 6 | title = Opposing effects of cis-9,trans-11 and trans-10,cis-12 conjugated linoleic acid on blood lipids in healthy humans | journal = The American Journal of Clinical Nutrition | volume = 80 | issue = 3 | pages = 614–20 | date = September 2004 | pmid = 15321800 | doi = 10.1093/ajcn/80.3.614 | doi-access = free }}

Some trans fatty acids occur in natural fats and traditionally processed foods. Vaccenic acid occurs in breast milk, and some isomers of conjugated linoleic acid (CLA) are found in meat and dairy products from ruminants. Butter, for example, contains about 3% trans fat.{{cite web | url=https://ndb.nal.usda.gov/ndb/foods/show/1?fgcd=&manu=&lfacet=&format=&count=&max=50&offset=50&sort=default&order=asc&qlookup=butter&ds=&qt=&qp=&qa=&qn=&q=&ing= | title=National Nutrient Database for Standard Reference Release 28 | publisher=United States Department of Agriculture}}{{dead link|date=October 2022|bot=medic}}{{cbignore|bot=medic}}

The U.S. National Dairy Council has asserted that the trans fats present in animal foods are of a different type than those in partially hydrogenated oils, and do not appear to exhibit the same negative effects.{{cite web | author=National Dairy Council | title=comments on 'Docket No. 2003N-0076 Food Labeling: Trans Fatty Acids in Nutrition Labeling' | website=Food and Drug Administration | date=18 June 2004 | url=https://www.fda.gov/ohrms/dockets/dailys/04/June04/062304/03N-0076-emc00228-01.pdf |archive-url=https://web.archive.org/web/20050516010336/http://www.fda.gov/ohrms/dockets/dailys/04/June04/062304/03N-0076-emc00228-01.pdf |archive-date=2005-05-16 | access-date=7 January 2007}} A review agrees with the conclusion (stating that "the sum of the current evidence suggests that the Public health implications of consuming trans fats from ruminant products are relatively limited") but cautions that this may be due to the low consumption of trans fats from animal sources compared to artificial ones.

In 2008 a meta-analysis found that all trans fats, regardless of natural or artificial origin equally raise LDL and lower HDL levels. Other studies though have shown different results when it comes to animal-based trans fats like conjugated linoleic acid (CLA). Although CLA is known for its anticancer properties, researchers have also found that the cis-9, trans-11 form of CLA can reduce the risk for cardiovascular disease and help fight inflammation.{{cite journal | vauthors = Zulet MA, Marti A, Parra MD, Martínez JA | title = Inflammation and conjugated linoleic acid: mechanisms of action and implications for human health | journal = Journal of Physiology and Biochemistry | volume = 61 | issue = 3 | pages = 483–94 | date = September 2005 | pmid = 16440602 | doi = 10.1007/BF03168454 | s2cid = 32082565 }}

File:Triglyceride Hydrogenation&Isomerization V.1.png

Partially hydrogenated vegetable oils were an increasingly significant part of the human diet for about 100 years, especially after 1950 as processed food rose in popularity.{{cite journal | vauthors = Valenzuela A, Morgado N | title = Trans fatty acid isomers in human health and in the food industry | journal = Biological Research | volume = 32 | issue = 4 | pages = 273–87 | year = 1999 | pmid = 10983247 | doi = 10.4067/s0716-97601999000400007 | doi-access = free }}

Animal-based fats were once the only trans fats consumed, but by far the largest amount of trans fat consumed today is created by the processed food industry as a side effect of partially hydrogenating unsaturated plant fats (generally vegetable oils). These partially hydrogenated fats have displaced natural solid fats and liquid oils in many areas, the most notable ones being in the fast food, snack food, fried food, and baked goods industries.{{cite book |last1=Ashok |first1=Chauhan |last2=Ajit |first2=Varma |date=2009 |page = 181 |chapter=Chapter 4: Fatty acids |title=A Textbook of Molecular Biotechnology |publisher=I. K. International Pvt |isbn=978-93-80026-37-4}}

Up to 45% of the total fat in those foods containing human-made trans fats formed by partially hydrogenating plant fats may be trans fat. An analysis of some industrialized foods in 2006 found up to 30% "trans fats" in artificial shortening, 10% in breads and cake products, 8% in cookies and crackers, 4% in salty snacks, 7% in cake frostings and sweets, and 26% in margarine and other processed spreads. Another 2010 analysis however found only 0.2% of trans fats in margarine and other processed spreads.{{cite news | title=Heart Foundation: Butter has 20 times the trans fats of marg {{!}} Australian Food News | url=http://www.ausfoodnews.com.au/2010/09/28/heart-foundation-butter-has-20-times-the-trans-fats-of-marg.html | work=www.ausfoodnews.com.au}}

Foods containing higher amounts of trans fat is associated with fast food restaurants. They are consumed in greater quantities by people who lack access to a diet consisting of fewer partially-hydrogenated fats, or who often consume fast food. A diet high in trans fats can contribute to obesity, high blood pressure, and higher risk for heart disease. Trans fat is also implicated in Type 2 diabetes.{{cite journal| first = Ulf | last = Riserus |title=Trans fatty acids, insulin sensitivity and type 2 diabetes|journal=Scandinavian Journal of Food and Nutrition|volume=50 |issue=4 |pages=161–165|year=2006|doi=10.1080/17482970601133114|doi-access=free}}

Shortenings, because they are widely used, are of particular concern. Baking shortenings, unless reformulated, contain around 30% trans fats compared to their total fats. High-fat dairy products such as butter contain about 4%. Margarines not reformulated to reduce trans fats may contain up to 15% trans fat by weight,{{cite journal| vauthors = Hunter JE | year=2005|title=Dietary levels of trans fatty acids" basis for health concerns and industry efforts to limit use|journal=Nutrition Research|volume=25|pages=499–513|doi=10.1016/j.nutres.2005.04.002|issue=5}} but some reformulated ones are less than 1% trans fat. Shortenings for deep-frying in restaurants can be used for longer than most conventional oils before becoming rancid. In the early 21st century, non-hydrogenated vegetable oils that have lifespans exceeding that of the frying shortenings became available.{{cite web|last=NYC Board of Health |title=Board of Health Approves Regulation to Phase Out Artificial Trans Fat: FAQ |url=http://www.nyc.gov/html/doh/html/cardio/cardio-transfat-healthcode-faq.shtml#7 |access-date=7 January 2007 |archive-url=https://web.archive.org/web/20061006022908/http://www.nyc.gov/html/doh/html/cardio/cardio-transfat-healthcode-faq.shtml |archive-date=6 October 2006}} In fast-food chains, trans fat levels in fast food can vary with location. For example, an analysis of samples of McDonald's French fries collected in 2004 and 2005 found that fries served in New York City contained twice as much trans fat as in Hungary, and 28 times as much as in Denmark, where trans fats are restricted. At KFC, the pattern was reversed, with Hungary's product containing twice the trans fat of the New York product. Even within the U.S. there was variation, with fries in New York containing 30% more trans fat than those from Atlanta.{{cite news|title=What's in that french fry? Fat varies by city|publisher=NBC News|date=12 April 2006|url=https://www.nbcnews.com/id/wbna12287818|access-date=7 January 2007}}{{dead link|date=August 2024|bot=medic}}{{cbignore|bot=medic}} AP story concerning {{cite journal | pmid = 16611965 | doi=10.1056/NEJMc052959 | volume=354 | title=High levels of industrially produced trans fat in popular fast foods | date=April 2006 | journal=N. Engl. J. Med. | pages=1650–2 | last1 = Stender | first1 = S | last2 = Dyerberg | first2 = J | last3 = Astrup | first3 = A| issue=15 | doi-access=free }}

File:Margaryn 022.jpg , a common product that can contain trans fatty acids]]

File:Crisco Cookbook 1912.jpg cookbook, 1912. Crisco was made by hydrogenating cottonseed oil. The formula was revised in the 2000s and now has only a small amount of trans fat.]]

File:Triglyceride Hydrogenation&Isomerization V.1.png

High levels of TFAs have been recorded in popular "fast food" meals. An analysis of samples of McDonald's French fries collected in 2004 and 2005 found that fries served in New York City contained twice as much trans fat as in Hungary, and 28 times as much as in Denmark, where trans fats are restricted. For Kentucky Fried Chicken products, the pattern was reversed: the Hungarian product containing twice the trans fat of the New York product. Even within the United States, there was variation, with fries in New York containing 30% more trans fat than those from Atlanta.{{cite news | title=What's in that french fry? Fat varies by city | work=NBC News | date=12 April 2006 | url=https://www.nbcnews.com/id/12287818 | archive-url=https://web.archive.org/web/20151017191934/http://www.nbcnews.com/id/12287818/ | url-status=dead | archive-date=October 17, 2015 | access-date=7 January 2007}} AP story concerning {{cite journal | pmid = 16611965 | doi=10.1056/NEJMc052959 | volume=354 | title=High levels of industrially produced trans fat in popular fast foods | date=April 2006 | journal=N. Engl. J. Med. | pages=1650–2 | last1 = Stender | first1 = S | last2 = Dyerberg | first2 = J | last3 = Astrup | first3 = A| issue=15 | doi-access=free }}

It has been established that trans fats in human breast milk fluctuate with maternal consumption of trans fat, and that the amount of trans fats in the bloodstream of breastfed infants fluctuates with the amounts found in their milk. In 1999, reported percentages of trans fats (compared to total fats) in human milk ranged from 1% in Spain, 2% in France, 4% in Germany, and 7% in Canada and the U.S.{{cite journal | vauthors = Innis SM, King DJ | title = trans Fatty acids in human milk are inversely associated with concentrations of essential all-cis n-6 and n-3 fatty acids and determine trans, but not n-6 and n-3, fatty acids in plasma lipids of breast-fed infants | journal = The American Journal of Clinical Nutrition | volume = 70 | issue = 3 | pages = 383–90 | date = September 1999 | pmid = 10479201 | doi = 10.1093/ajcn/70.3.383 | doi-access = free }}

{{main | Trans fat regulation}}

In the last few decades, there has been substantial amount of regulation in many countries, limiting trans fat contents of industrialized and commercial food products.

In light of recognized evidence and scientific agreement, nutritional authorities consider all trans fats equally harmful for health and recommend that their consumption be reduced to trace amounts. In 2003, the WHO recommended that trans fats make up no more than 0.9% of a person's diet and, in 2018, introduced a 6-step guide to eliminate industrially-produced trans-fatty acids from the global food supply.{{cite press release | title=WHO plan to eliminate industrially-produced trans-fatty acids from global food supply | url=https://www.who.int/news-room/detail/14-05-2018-who-plan-to-eliminate-industrially-produced-trans-fatty-acids-from-global-food-supply | publisher=World Health Organization | date=14 May 2018}}

The National Academy of Sciences (NAS) advises the U.S. and Canadian governments on nutritional science for use in public policy and product labeling programs. Their 2002 Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids{{cite book | last=Food and nutrition board, institute of medicine of the national academies | title=Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) | publisher=National Academies Press | year=2005 | page=i | url=http://darwin.nap.edu/books/0309085373/html/R1.html | archive-url=https://web.archive.org/web/20060918061042/http://darwin.nap.edu/books/0309085373/html/R1.html | archive-date=18 September 2006}} contains their findings and recommendations regarding consumption of trans fat.[http://www.nap.edu/openbook/0309085373/html/423.html Summary] {{Webarchive|url=https://web.archive.org/web/20070625193000/http://www.nap.edu/openbook/0309085373/html/423.html|date=2007-06-25}}.

Their recommendations are based on two key facts. First, "trans fatty acids are not essential and provide no known benefit to human health",{{cite book|last=Food and nutrition board, institute of medicine of the national academies|title=Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients)|publisher=National Academies Press|year=2005|pages=[https://archive.org/details/isbn_9780309085250/page/423 423]|url=https://archive.org/details/isbn_9780309085250/page/423|doi=10.17226/10490|isbn=978-0-309-08525-0}} whether of animal or plant origin.{{cite book | last=Food and nutrition board, institute of medicine of the national academies | title=Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) | publisher=National Academies Press | year=2005 | page = 447 | url=http://darwin.nap.edu/books/0309085373/html/447.html}}{{dead link | date=January 2018 | bot=InternetArchiveBot | fix-attempted=yes}} Second, given their documented effects on the LDL/HDL ratio, the NAS concluded "that dietary trans fatty acids are more deleterious with respect to coronary artery disease than saturated fatty acids". A 2006 review stated "from a nutritional standpoint, the consumption of trans fatty acids results in considerable potential harm but no apparent benefit."

Because of these facts and concerns, the NAS has concluded there is no safe level of trans fat consumption. There is no adequate level, recommended daily amount or tolerable upper limit for trans fats. This is because any incremental increase in trans fat intake increases the risk of coronary artery disease.

Despite this concern, the NAS dietary recommendations have not included eliminating trans fat from the diet. This is because trans fat is naturally present in many animal foods in trace quantities, and thus its removal from ordinary diets might introduce undesirable side effects and nutritional imbalances. The NAS has, thus, "recommended that trans fatty acid consumption be as low as possible while consuming a nutritionally adequate diet".{{cite book | last=Food and nutrition board, institute of medicine of the national academies | title=Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) | publisher=National Academies Press | year=2005 | page = 424 | url=http://darwin.nap.edu/books/0309085373/html/424.html}}{{dead link | date=January 2018 | bot=InternetArchiveBot | fix-attempted=yes}} Like the NAS, the WHO has tried to balance public health goals with a practical level of trans fat consumption, recommending in 2003 that trans fats be limited to less than 1% of overall energy intake.

While trans fatty acids (popularly called "trans fats") are edible, they have been implicated in many health problems.{{cite journal | vauthors = Menaa F, Menaa A, Menaa B, Tréton J | title = Trans-fatty acids, dangerous bonds for health? A background review paper of their use, consumption, health implications and regulation in France | journal = European Journal of Nutrition | volume = 52 | issue = 4 | pages = 1289–302 | date = June 2013 | pmid = 23269652 | doi = 10.1007/s00394-012-0484-4 | s2cid = 206968361 }}

The primary health risk identified for trans fat consumption is an elevated risk of coronary artery disease (CAD).[https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/fats-and-cholesterol/ "Fats and Cholesterol"] {{Webarchive|url=https://web.archive.org/web/20161118054242/https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/fats-and-cholesterol/ |date=2016-11-18 }}, Harvard School of Public Health. Retrieved 02-11-16.Government of the United Kingdom (1996): "[http://www.legislation.gov.uk/uksi/1996/1499/schedule/7/made Schedule 7: Nutrition labelling] {{Webarchive|url=https://web.archive.org/web/20130317110033/http://www.legislation.gov.uk/uksi/1996/1499/schedule/7/made |date=2013-03-17 }}". In [http://www.legislation.gov.uk/uksi/1996/1499/contents/made Food Labelling Regulations 1996] {{Webarchive|url=https://web.archive.org/web/20130921164025/http://www.legislation.gov.uk/uksi/1996/1499/contents/made |date=2013-09-21 }}. Accessed on 2020-08-09.{{cite web | author=Trans Fat Task Force | title=TRANSforming the Food Supply, Appendix 9iii | date=June 2006 |url=http://www.hc-sc.gc.ca/fn-an/nutrition/gras-trans-fats/tf-ge/tf-gt_app9iii_e.html | access-date=9 January 2007 | archive-url=https://web.archive.org/web/20070225021532/http://www.hc-sc.gc.ca/fn-an/nutrition/gras-trans-fats/tf-ge/tf-gt_app9iii_e.html | archive-date=25 February 2007}} (Consultation on the health implications of alternatives to trans fatty acids: Summary of Responses from Experts) A 1994 study estimated that over 30,000 cardiac deaths per year in the United States are attributable to the consumption of trans fats. By 2006 upper estimates of 100,000 deaths were suggested.{{cite journal | vauthors = Zaloga GP, Harvey KA, Stillwell W, Siddiqui R | title = Trans fatty acids and coronary heart disease | journal = Nutrition in Clinical Practice | volume = 21 | issue = 5 | pages = 505–12 | date = October 2006 | pmid = 16998148 | doi = 10.1177/0115426506021005505 }}

Major evidence for the effect of trans fat on CAD comes from the Nurses' Health Study – a cohort study that has been following 120,000 female nurses since its inception in 1976. In this study, Hu and colleagues analyzed data from 900 coronary events from the study's population during 14 years of followup. He determined that a nurse's CAD risk roughly doubled (relative risk of 1.93, CI: 1.43 to 2.61) for each 2% increase in trans fat calories consumed (instead of carbohydrate calories). By contrast, for each 5% increase in saturated fat calories (instead of carbohydrate calories) there was a 17% increase in risk (relative risk of 1.17, CI: 0.97 to 1.41). "The replacement of saturated fat or trans unsaturated fat by cis (unhydrogenated) unsaturated fats was associated with larger reductions in risk than an isocaloric replacement by carbohydrates." Hu also reports on the benefits of reducing trans fat consumption. Replacing 2% of food energy from trans fat with non-trans unsaturated fats more than halves the risk of CAD (53%). By comparison, replacing a larger 5% of food energy from saturated fat with non-trans unsaturated fats reduces the risk of CAD by 43%.

Another study considered deaths due to CAD, with consumption of trans fats being linked to an increase in mortality, and consumption of polyunsaturated fats being linked to a decrease in mortality.{{cite journal | vauthors = Oh K, Hu FB, Manson JE, Stampfer MJ, Willett WC | title = Dietary fat intake and risk of coronary heart disease in women: 20 years of follow-up of the nurses' health study | journal = American Journal of Epidemiology | volume = 161 | issue = 7 | pages = 672–9 | date = April 2005 | pmid = 15781956 | doi = 10.1093/aje/kwi085 | doi-access = free }}

Consuming trans fats has been shown to increase the risk of coronary artery disease in part by raising levels of low-density lipoprotein (LDL, often termed "bad cholesterol"), lowering levels of high-density lipoprotein (HDL, often termed "good cholesterol"), increasing triglycerides in the bloodstream and promoting systemic inflammation.{{cite book | last=Food and nutrition board, institute of medicine of the national academies | title=Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients) | publisher=National Academies Press | year=2005 | page = 504 | url=http://darwin.nap.edu/books/0309085373/html/504.html}}{{dead link | date=September 2017 | bot=InternetArchiveBot | fix-attempted=yes}}

Trans fat has been found to act like saturated in raising the blood level of LDL ("bad cholesterol"); but, unlike saturated fat, it also decreases levels of HDL ("good cholesterol"). The net increase in LDL/HDL ratio with trans fat, a widely accepted indicator of risk for coronary artery disease, is approximately double that due to saturated fat.{{cite journal | vauthors = Ascherio A, Katan MB, Zock PL, Stampfer MJ, Willett WC | title = Trans fatty acids and coronary heart disease | journal = The New England Journal of Medicine | volume = 340 | issue = 25 | pages = 1994–8 | date = June 1999 | pmid = 10379026 | doi = 10.1056/NEJM199906243402511 | s2cid = 30165590 }}{{cite journal | vauthors = Mensink RP, Katan MB | title = Effect of dietary trans fatty acids on high-density and low-density lipoprotein cholesterol levels in healthy subjects | journal = The New England Journal of Medicine | volume = 323 | issue = 7 | pages = 439–45 | date = August 1990 | pmid = 2374566 | doi = 10.1056/NEJM199008163230703 | url = http://library.wur.nl/WebQuery/wurpubs/13110 | doi-access = free }}{{cite journal | vauthors = Mensink RP, Zock PL, Kester AD, Katan MB | title = Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials | journal = The American Journal of Clinical Nutrition | volume = 77 | issue = 5 | pages = 1146–55 | date = May 2003 | pmid = 12716665 | doi = 10.1093/ajcn/77.5.1146 | doi-access = free }} One randomized crossover study published in 2003 comparing the effect of eating a meal on blood lipids of (relatively) cis and trans-fat-rich meals showed that cholesteryl ester transfer (CET) was 28% higher after the trans meal than after the cis meal and that lipoprotein concentrations were enriched in apolipoprotein(a) after the trans meals.{{cite journal | vauthors = Gatto LM, Sullivan DR, Samman S | title = Postprandial effects of dietary trans fatty acids on apolipoprotein(a) and cholesteryl ester transfer | journal = The American Journal of Clinical Nutrition | volume = 77 | issue = 5 | pages = 1119–24 | date = May 2003 | pmid = 12716661 | doi = 10.1093/ajcn/77.5.1119 | doi-access = free }}

The citokyne test is a potentially more reliable indicator of CAD risk, although is still being studied. A study of over 700 nurses showed that those in the highest quartile of trans fat consumption had blood levels of C-reactive protein (CRP) that were 73% higher than those in the lowest quartile.{{cite journal | vauthors = Lopez-Garcia E, Schulze MB, Meigs JB, Manson JE, Rifai N, Stampfer MJ, Willett WC, Hu FB | display-authors = 6 | title = Consumption of trans fatty acids is related to plasma biomarkers of inflammation and endothelial dysfunction | journal = The Journal of Nutrition | volume = 135 | issue = 3 | pages = 562–6 | date = March 2005 | pmid = 15735094 | doi = 10.1093/jn/135.3.562 | doi-access = free }}

Intake of dietary trans fat perturbs the body's ability to metabolize essential fatty acids (EFAs, including omega-3) leading to changes in the phospholipid fatty acid composition of the arterial walls, thereby raising risk of coronary artery disease.{{cite journal | vauthors = Kummerow FA, Zhou Q, Mahfouz MM, Smiricky MR, Grieshop CM, Schaeffer DJ | title = Trans fatty acids in hydrogenated fat inhibited the synthesis of the polyunsaturated fatty acids in the phospholipid of arterial cells | journal = Life Sciences | volume = 74 | issue = 22 | pages = 2707–23 | date = April 2004 | pmid = 15043986 | doi = 10.1016/j.lfs.2003.10.013 }}

There are two accepted tests that measure an individual's risk for coronary artery disease, both blood tests. The first considers ratios of two types of cholesterol, the other the amount of a cell-signalling cytokine called C-reactive protein. The effect of trans fat consumption has been documented on each as follows:

• Cholesterol ratio: This ratio compares the levels of LDL to HDL. Trans fat behaves like saturated fat by raising the level of LDL, but, unlike saturated fat, it has the additional effect of decreasing levels of HDL. The net increase in LDL/HDL ratio with trans fat is approximately double that due to saturated fat. (Higher ratios are worse.) One randomized crossover study published in 2003 comparing the effect of eating a meal on blood lipids of (relatively) cis and trans fat rich meals showed that cholesteryl ester transfer (CET) was 28% higher after the trans meal than after the cis meal and that lipoprotein concentrations were enriched in apolipoprotein(a) after the trans meals.{{cite journal | vauthors = Gatto LM, Sullivan DR, Samman S | title = Postprandial effects of dietary trans fatty acids on apolipoprotein(a) and cholesteryl ester transfer | journal = The American Journal of Clinical Nutrition | volume = 77 | issue = 5 | pages = 1119–24 | date = May 2003 | pmid = 12716661 | doi = 10.1093/ajcn/77.5.1119 | doi-access = }}
• C-reactive protein (CRP): A study of over 700 nurses showed that those in the highest quartile of trans fat consumption had blood levels of CRP that were 73% higher than those in the lowest quartile.

The mechanisms through which trans fatty acids contribute to coronary artery disease are fairly well understood. The mechanism for their effects on diabetes is still under investigation. They may impair the metabolism of long-chain polyunsaturated fatty acids (LCPUFAs).{{cite journal | vauthors = Mojska H | title = Influence of trans fatty acids on infant and fetus development | journal = Acta Microbiologica Polonica | volume = 52 Suppl | pages = 67–74 | year = 2003 | pmid = 15058815 }} However, maternal pregnancy trans fatty acid intake has been inversely associated with LCPUFAs levels in infants at birth thought to underlie the positive association between breastfeeding and intelligence.{{cite journal | vauthors = Koletzko B, Decsi T | title = Metabolic aspects of trans fatty acids | journal = Clinical Nutrition | volume = 16 | issue = 5 | pages = 229–37 | date = October 1997 | pmid = 16844601 | doi = 10.1016/s0261-5614(97)80034-9 }}

Trans fats are processed by the liver differently than other fats. They may cause liver dysfunction by interfering with delta 6 desaturase, an enzyme involved in converting essential fatty acids to arachidonic acid and prostaglandins, both of which are important to the functioning of cells.{{cite journal | vauthors = Mahfouz M | title = Effect of dietary trans fatty acids on the delta 5, delta 6 and delta 9 desaturases of rat liver microsomes in vivo | journal = Acta Biologica et Medica Germanica | volume = 40 | issue = 12 | pages = 1699–1705 | year = 1981 | pmid = 7345825 }}

Intake of dietary trans fat disrupts the body's ability to metabolize essential fatty acids (EFAs, including Omega-3) leading to changes in the phospholipid fatty acid composition of the arterial walls, thereby raising risk of coronary artery disease.

The major evidence for the effect of trans fat on CAD comes from the Nurses' Health Study – a cohort study that has been following 120,000 female nurses since its inception in 1976. In this study, Hu and colleagues analyzed data from 900 coronary events from the study's population during 14 years of followup. He determined that a nurse's CAD risk roughly doubled (relative risk of 1.93, CI: 1.43 to 2.61) for each 2% increase in trans fat calories consumed (instead of carbohydrate calories). By contrast, for each 5% increase in saturated fat calories (instead of carbohydrate calories) there was a 17% increase in risk (relative risk of 1.17, CI: 0.97 to 1.41). "The replacement of saturated fat or trans unsaturated fat by cis (unhydrogenated) unsaturated fats was associated with larger reductions in risk than an isocaloric replacement by carbohydrates."{{cite journal | vauthors = Hu FB, Stampfer MJ, Manson JE, Rimm E, Colditz GA, Rosner BA, Hennekens CH, Willett WC | display-authors = 6 | title = Dietary fat intake and the risk of coronary heart disease in women | journal = The New England Journal of Medicine | volume = 337 | issue = 21 | pages = 1491–9 | date = November 1997 | pmid = 9366580 | doi = 10.1056/NEJM199711203372102 | doi-access = free }} Hu also reports on the benefits of reducing trans fat consumption. Replacing 2% of food energy from trans fat with non-trans unsaturated fats more than halves the risk of CAD (53%). By comparison, replacing a larger 5% of food energy from saturated fat with non-trans unsaturated fats reduces the risk of CAD by 43%.

Another study considered deaths due to CAD, with consumption of trans fats being linked to an increase in mortality, and consumption of polyunsaturated fats being linked to a decrease in mortality.

Scientific studies have examined other negative effects of industrial trans fat beyond cardiovascular disease, with the next most studied area being type-2 diabetes.

• Alzheimer's disease: A study published in Archives of Neurology in February 2003 suggested that the intake of both trans fats and saturated fats promote the development of Alzheimer disease,{{cite journal | vauthors = Morris MC, Evans DA, Bienias JL, Tangney CC, Bennett DA, Aggarwal N, Schneider J, Wilson RS | display-authors = 6 | title = Dietary fats and the risk of incident Alzheimer disease | journal = Archives of Neurology | volume = 60 | issue = 2 | pages = 194–200 | date = February 2003 | pmid = 12580703 | doi = 10.1001/archneur.60.2.194 | doi-access = }} although not confirmed in an animal model. It has been found that trans fats impaired memory and learning in middle-age rats. The trans-fat eating rats' brains had fewer proteins critical to healthy neurological function and inflammation in and around the hippocampus, the part of the brain responsible for learning and memory. These are the exact types of changes normally seen at the onset of Alzheimer's, but seen after six weeks, even though the rats were still young.{{cite journal | vauthors = Granholm AC, Bimonte-Nelson HA, Moore AB, Nelson ME, Freeman LR, Sambamurti K | title = Effects of a saturated fat and high cholesterol diet on memory and hippocampal morphology in the middle-aged rat | journal = Journal of Alzheimer's Disease | volume = 14 | issue = 2 | pages = 133–45 | date = June 2008 | pmid = 18560126 | pmc = 2670571 | doi = 10.3233/JAD-2008-14202 }} A systematic review of five articles based on four prospective cohort studies of individuals did not find a robust association between their intake of trans fatty acids and development of Alzheimer's disease (or several other forms of dementia). The review based this conclusion on finding that 4 of the 5 reports appeared biased and therefore recommended more well-designed prospective studies to clarify this issue.{{cite journal | vauthors = Nwaru BI, Dierkes J, Ramel A, Arnesen EK, Thorisdottir B, Lamberg-Allardt C, Söderlund F, Bärebring L, Åkesson A | title = Quality of dietary fat and risk of Alzheimer's disease and dementia in adults aged ≥50 years: a systematic review | journal = Food & Nutrition Research | volume = 66 | date = 2022 | pmid = 35950105 | pmc = 9338447 | doi = 10.29219/fnr.v66.8629 }}
• Cancer: In 2007 the American Cancer Society stated that a relationship between trans fats and cancer "has not been determined."{{cite web|last=American Cancer Society|title=Common questions about diet and cancer|url=https://www.cancer.org/docroot/ped/content/ped_3_2x_common_questions_about_diet_and_cancer.asp|access-date=9 January 2007|archive-date=13 April 2010|archive-url=https://web.archive.org/web/20100413182919/http://www.cancer.org/docroot/PED/content/PED_3_2X_Common_Questions_About_Diet_and_Cancer.asp|url-status=dead}} One study has found a positive connection between trans fat and prostate cancer.{{cite journal| vauthors = Chavarro J, Stampfer M, Campos H, Kurth T, Willett W, Ma J |title=A prospective study of blood trans fatty acid levels and risk of prostate cancer|journal=Proc. Amer. Assoc. Cancer Res.|volume=47|date=1 April 2006|url=http://www.aacrmeetingabstracts.org/cgi/content/abstract/2006/1/943|access-date=9 January 2007|issue=1|page = 943}} However, a larger study found a correlation between trans fats and a significant decrease in high-grade prostate cancer.{{cite journal | vauthors = Brasky TM, Till C, White E, Neuhouser ML, Song X, Goodman P, Thompson IM, King IB, Albanes D, Kristal AR | display-authors = 6 | title = Serum phospholipid fatty acids and prostate cancer risk: results from the prostate cancer prevention trial | journal = American Journal of Epidemiology | volume = 173 | issue = 12 | pages = 1429–39 | date = June 2011 | pmid = 21518693 | pmc = 3145396 | doi = 10.1093/aje/kwr027 }} An increased intake of trans fatty acids may raise the risk of breast cancer by 75%, suggest the results from the French part of the European Prospective Investigation into Cancer and Nutrition.{{cite press release|url=https://www.iarc.who.int/ENG/Press_Releases/pr184a.html |title=Breast cancer: a role for trans fatty acids? |work=World Health Organization |date=11 April 2008 |archive-url=https://web.archive.org/web/20080413023008/http://www.iarc.fr/ENG/Press_Releases/pr184a.html |archive-date=13 April 2008}}{{cite journal | vauthors = Chajès V, Thiébaut AC, Rotival M, Gauthier E, Maillard V, Boutron-Ruault MC, Joulin V, Lenoir GM, Clavel-Chapelon F | display-authors = 6 | title = Association between serum trans-monounsaturated fatty acids and breast cancer risk in the E3N-EPIC Study | journal = American Journal of Epidemiology | volume = 167 | issue = 11 | pages = 1312–20 | date = June 2008 | pmid = 18390841 | pmc = 2679982 | doi = 10.1093/aje/kwn069 }}
• Diabetes: There is a growing concern that the risk of type 2 diabetes increases with trans fat consumption. However, consensus has not been reached. For example, one study found that risk is higher for those in the highest quartile of trans fat consumption.{{cite journal | vauthors = Hu FB, van Dam RM, Liu S | title = Diet and risk of Type II diabetes: the role of types of fat and carbohydrate | journal = Diabetologia | volume = 44 | issue = 7 | pages = 805–17 | date = July 2001 | pmid = 11508264 | doi = 10.1007/s001250100547 | doi-access = free }} Another study has found no diabetes risk once other factors such as total fat intake and BMI were accounted for.{{cite journal | vauthors = van Dam RM, Willett WC, Rimm EB, Stampfer MJ, Hu FB | title = Dietary fat and meat intake in relation to risk of type 2 diabetes in men | journal = Diabetes Care | volume = 25 | issue = 3 | pages = 417–24 | date = March 2002 | pmid = 11874924 | doi = 10.2337/diacare.25.3.417 | doi-access = free }}
• Obesity: Research indicates that trans fat may increase weight gain and abdominal fat, despite a similar caloric intake.{{cite news|last=Gosline|first=Anna |title=Why fast foods are bad, even in moderation|work=New Scientist|date=12 June 2006|url=https://www.newscientist.com/article.ns/?id=dn9318|access-date=9 January 2007}} A 6-year experiment revealed that monkeys fed a trans fat diet gained 7.2% of their body weight, as compared to 1.8% for monkeys on a mono-unsaturated fat diet.{{cite journal |url= https://www.newscientist.com/channel/health/mg19025565.000-six-years-of-fastfood-fats-supersizes-monkeys.html |title=Six years of fast-food fats supersizes monkeys |journal=New Scientist |issue=2556 |date=17 June 2006 |page = 21 }}{{cite journal | vauthors = Kavanagh K, Jones KL, Sawyer J, Kelley K, Carr JJ, Wagner JD, Rudel LL | title = Trans fat diet induces abdominal obesity and changes in insulin sensitivity in monkeys | journal = Obesity | volume = 15 | issue = 7 | pages = 1675–84 | date = July 2007 | pmid = 17636085 | doi = 10.1038/oby.2007.200 | s2cid = 4835948 | doi-access = free }} Although obesity is frequently linked to trans fat in the popular media,{{cite news |url=https://www.hhs.gov/news/speech/2003/030709.html |title=Trans Fat Press Conference | last = Thompson | first = Tommy G |archive-url=https://web.archive.org/web/20060709233042/http://www.hhs.gov/news/speech/2003/030709.html |archive-date=9 July 2006 }}, US Secretary of health and human services this is generally in the context of eating too many calories; there is not a strong scientific consensus connecting trans fat and obesity, although the 6-year experiment did find such a link, concluding that "under controlled feeding conditions, long-term TFA consumption was an independent factor in weight gain. TFAs enhanced intra-abdominal deposition of fat, even in the absence of caloric excess, and were associated with insulin resistance, with evidence that there is impaired post-insulin receptor binding signal transduction."
• Liver dysfunction: Trans fats are metabolized differently by the liver than other fats and interfere with delta 6 desaturase. Delta 6 desaturase is an enzyme involved in converting essential fatty acids to arachidonic acid and prostaglandins, both of which are important to the functioning of cells.
• Infertility in women: One 2007 study found, "Each 2% increase in the intake of energy from trans unsaturated fats, as opposed to that from carbohydrates, was associated with a 73% greater risk of ovulatory infertility...".{{cite journal | vauthors = Chavarro JE, Rich-Edwards JW, Rosner BA, Willett WC | title = Dietary fatty acid intakes and the risk of ovulatory infertility | journal = The American Journal of Clinical Nutrition | volume = 85 | issue = 1 | pages = 231–7 | date = January 2007 | pmid = 17209201 | doi = 10.1093/ajcn/85.1.231 | doi-access = free }}
• Major depressive disorder: Spanish researchers analysed the diets of 12,059 people over six years and found that those who ate the most trans fats had a 48 per cent higher risk of depression than those who did not eat trans fats.{{cite news|title=Trans fats and saturated fats could contribute to depression|url=https://www.smh.com.au/lifestyle/health-and-wellness/food-with-bad-fats-linked-to-depression-study-finds-20110127-1a6vy.html|work=The Sydney Morning Herald|date=28 January 2011|access-date=8 February 2011|first=Shari|last=Roan }} One mechanism may be trans-fats' substitution for docosahexaenoic acid (DHA) levels in the orbitofrontal cortex (OFC). Very high intake of trans-fatty acids (43% of total fat) in mice from 2 to 16 months of age was associated with lowered DHA levels in the brain (p=0.001).{{cite journal | vauthors = Phivilay A, Julien C, Tremblay C, Berthiaume L, Julien P, Giguère Y, Calon F | title = High dietary consumption of trans fatty acids decreases brain docosahexaenoic acid but does not alter amyloid-beta and tau pathologies in the 3xTg-AD model of Alzheimer's disease | journal = Neuroscience | volume = 159 | issue = 1 | pages = 296–307 | date = March 2009 | pmid = 19135506 | doi = 10.1016/j.neuroscience.2008.12.006 | s2cid = 35748183 }} When the brains of 15 major depressive subjects who had committed suicide were examined post-mortem and compared against 27 age-matched controls, the suicidal brains were found to have 16% less (male average) to 32% less (female average) DHA in the OFC. The OFC controls reward, reward expectation, and empathy (all of which are reduced in depressive mood disorders) and regulates the limbic system.{{cite journal | vauthors = McNamara RK, Hahn CG, Jandacek R, Rider T, Tso P, Stanford KE, Richtand NM | title = Selective deficits in the omega-3 fatty acid docosahexaenoic acid in the postmortem orbitofrontal cortex of patients with major depressive disorder | journal = Biological Psychiatry | volume = 62 | issue = 1 | pages = 17–24 | date = July 2007 | pmid = 17188654 | doi = 10.1016/j.biopsych.2006.08.026 | s2cid = 32898004 | url = http://www.biologicalpsychiatryjournal.com/article/S0006-3223(06)01065-1/abstract }}
• Behavioral irritability and aggression: a 2012 observational analysis of subjects of an earlier study found a strong relation between dietary trans fat acids and self-reported behavioral aggression and irritability, suggesting but not establishing causality.{{cite journal | vauthors = Golomb BA, Evans MA, White HL, Dimsdale JE | title = Trans fat consumption and aggression | journal = PLOS ONE | volume = 7 | issue = 3 | pages = e32175 | year = 2012 | pmid = 22403632 | pmc = 3293881 | doi = 10.1371/journal.pone.0032175 | bibcode = 2012PLoSO...732175G | doi-access = free }}
• Diminished memory: In a 2015 article, researchers re-analyzing results from the 1999-2005 UCSD Statin Study argue that "greater dietary trans fatty acid consumption is linked to worse word memory in adults during years of high productivity."{{cite journal | vauthors = Golomb BA, Bui AK | title = A Fat to Forget: Trans Fat Consumption and Memory | journal = PLOS ONE | volume = 10 | issue = 6 | pages = e0128129 | year = 2015 | pmid = 26083739 | pmc = 4470692 | doi = 10.1371/journal.pone.0128129 | bibcode = 2015PLoSO..1028129G | doi-access = free }}
• Acne: According to a 2015 study, trans fats are one of several components of Western pattern diets which promote acne, along with carbohydrates with high glycemic load such as refined sugars or refined starches, milk and dairy products, and saturated fats, while omega-3 fatty acids, which reduce acne, are deficient in Western pattern diets.{{cite journal | vauthors = Melnik BC | title = Linking diet to acne metabolomics, inflammation, and comedogenesis: an update | journal = Clinical, Cosmetic and Investigational Dermatology | volume = 8 | pages = 371–88 | date = 15 July 2015 | pmid = 26203267 | pmc = 4507494 | doi = 10.2147/CCID.S69135 | editor1-last = Weinberg | editor1-first = Jeffrey | doi-access = free }}

Palm oil, a natural oil extracted from the fruit of oil palm trees that is semi-solid at room temperature (15–25 degrees Celsius), can potentially serve as a substitute for partially hydrogenated fats in baking and processed food applications, although there is disagreement about whether replacing partially hydrogenated fats with palm oil confers any health benefits. A 2006 study supported by the National Institutes of Health and the USDA Agricultural Research Service concluded that palm oil is not a safe substitute for partially hydrogenated fats (trans fats) in the food industry, because palm oil results in adverse changes in the blood concentrations of LDL and apolipoprotein B just as trans fat does.{{cite journal | vauthors = Vega-López S, Ausman LM, Jalbert SM, Erkkilä AT, Lichtenstein AH | title = Palm and partially hydrogenated soybean oils adversely alter lipoprotein profiles compared with soybean and canola oils in moderately hyperlipidemic subjects | journal = The American Journal of Clinical Nutrition | volume = 84 | issue = 1 | pages = 54–62 | date = July 2006 | pmid = 16825681 | doi = 10.1093/ajcn/84.1.54 | doi-access = free }}{{cite news |url=https://www.sciencedaily.com/releases/2009/05/090502084827.htm |title=Palm oil not a healthy substitute for trans fats, study finds|date=11 May 2009 |work=ScienceDaily |access-date=12 May 2010}}

In May 2003, BanTransFats.com Inc., a U.S. non-profit corporation, filed a lawsuit against the food manufacturer Kraft Foods in an attempt to force Kraft to remove trans fats from the Oreo cookie. The lawsuit was withdrawn when Kraft agreed to work on ways to find a substitute for the trans fat in the Oreo.

The J.M. Smucker Company, then the American manufacturer of Crisco (the original partially hydrogenated vegetable shortening), in 2004 released a new formulation made from solid saturated palm oil cut with soybean oil and sunflower oil. This blend yielded an equivalent shortening much like the prior partially hydrogenated Crisco, and was labelled zero grams of trans fat per 1 tablespoon serving (as compared with 1.5 grams per tablespoon of original Crisco).{{cite web|title=Crisco 0 grams trans fat per serving all-vegetable shortening|url=https://crisco.com/about/prod_info.asp?groupID=17&catId=63&FlavorId=344|access-date=18 January 2007|archive-url=https://web.archive.org/web/20061015192538/http://crisco.com/about/prod_info.asp?groupID=17&catId=63&FlavorId=344|archive-date=15 October 2006}} As of 24 January 2007, Smucker said that all Crisco shortening products in the US had been reformulated to contain less than one gram of trans fat per serving while keeping saturated fat content less than butter."{{cite web|url=https://crisco.com/about/shortening_0gramstransfat_faq.asp|archive-url=https://web.archive.org/web/20070927202746/http://crisco.com/about/shortening_0gramstransfat_faq.asp|title=Crisco Frequently Asked Questions|archive-date=27 September 2007}} The separately marketed trans fat free version introduced in 2004 was discontinued.

On 22 May 2004, Unilever, the corporate descendant of Joseph Crosfield & Sons (the original producer of Wilhelm Normann's hydrogenation hardened oils) announced that they had eliminated trans fats from all their margarine products in Canada, including their flagship Becel brand.{{cite web|archive-url=https://web.archive.org/web/20070927093711/http://www.fcpc.ca/issues/hal/transfat.html|title=List of Canadian industry actions to reduce transfats|publisher=Food & Consumer Products of Canada (FCPC)|access-date=13 September 2007|archive-date=27 September 2007|url=http://www.fcpc.ca/issues/hal/transfat.html}}

Agribusiness giant Bunge Limited, through their Bunge Oils division, produce an NT product line of non-hydrogenated oils, margarines and shortenings, made from corn, canola, and soy oils.{{cite web|url=http://www.transfatsolutions.com|title=Welcome to TransFatSolutions.com powered by Bunge|publisher=Transfatsolutions.com|access-date=14 July 2011}}

Beginning around 2000, as the scientific evidence and public concern about trans fat increased, major American users of trans fat began to switch to safer alternatives. The process received a large boost in 2003 when the FDA announced it would require trans fat labeling on packaged food starting in 2006. Packaged food companies then faced the choice of either eliminating trans fat from their products, or having to declare the trans fat on their nutrition label. Lawsuits in the U.S. against trans fat users also encouraged its removal.

Major American fast food chains including McDonald's, Burger King, KFC and Wendy's reduced and then removed partially hydrogenated oils (containing artificial trans fats) by 2009. This was a major step toward trans fat removal, as french fries were one of the largest sources of trans fat in the American diet, with a large serving of fries typically having about 6 grams of trans fat until around 2007.{{Cite journal|last=Urban|first=Lorien E.|date=2014|title=Temporal Trends in Fast-Food Restaurant Energy, Sodium, Saturated Fat, and Trans Fat Content, United States, 1996–2013|url=https://www.cdc.gov/pcd/issues/2014/14_0202.htm|journal=Preventing Chronic Disease|volume=11|pages=E229 |doi=10.5888/pcd11.140202|pmid=25551184 |pmc=4283359 |issn=1545-1151}}{{cite web|date=24 March 2010|title=Trans Fat Food Industry Response|url=https://www.news-medical.net/health/Trans-Fat-Food-Industry-Response.aspx|publisher=News-Medical.net}}{{cite press release|title=KFC Sued for Fouling Chicken with Partially Hydrogenated Oil: Lawsuit Aimed at Eliminating, or Disclosing Use of Artery-Clogging Frying Oil|publisher=Center for Science in the Public Interest|date=12 June 2006|url=https://www.cspinet.org/news/kfc-sued-fouling-chicken-partially-hydrogenated-oil-20060612|access-date=18 January 2007}}{{cite web|date=12 June 2006|title=Class action complaint|url=https://www.cspinet.org/sites/default/files/media/documents/resource/final_complaint.pdf|access-date=18 January 2007}}{{cite news|last=Burros|first=Marian|date=14 June 2006|title=KFC Is Sued Over the Use of Trans Fats in Its Cooking|work=The New York Times|url=https://www.nytimes.com/2006/06/14/us/14fat.html?ex=1307937600&en=01d0b7b6b5c00eb6&ei=5088&partner=rssnyt&emc=rss|access-date=18 January 2007}}{{cite press release|title=KFC announces switch to zero trans fat cooking oil following two-year test for same great taste|publisher=KFC|date=30 October 2006|url=http://www.kfc.com/about/pressreleases/103006.asp|archive-url=https://web.archive.org/web/20070119110204/http://www.kfc.com/about/pressreleases/103006.asp|archive-date=19 January 2007|access-date=18 January 2007}}{{cite press release|title=KFC Canada phasing in zero grams trans fat menu in all 786 restaurants nationally early in the new year|publisher=KFC Canada|date=30 October 2006|url=http://www.cnw.ca/en/releases/archive/October2006/30/c5869.html|archive-url=https://web.archive.org/web/20070218113648/http://www.cnw.ca/en/releases/archive/October2006/30/c5869.html|archive-date=18 February 2007|access-date=18 January 2007}}{{cite press release|title=Wendy's Significantly Cuts Trans Fats – Switch to New Cooking Oil Under Way|publisher=Wendy's|date=8 June 2006|url=https://www.wendys.com/about_us/news/index.jsp?news=5|archive-url=https://web.archive.org/web/20061109131923/http://www.wendys.com/about_us/news/index.jsp?news=5|archive-date=9 November 2006|access-date=11 April 2013}}

Two other events were important in the removal of trans fat. First, in 2013 the FDA announced it planned to completely ban artificial trans fat in the form of partially hydrogenated oil. Second, soon after this, Walmart informed its suppliers they needed to remove trans fat by 2015 if they wanted to continue to sell their products at its stores. As Walmart is the largest brick-and-mortar retailer in the U.S., mainstream food brands had little choice but to comply.{{cite news|url=https://www.nbcnews.com/id/wbna16873869|title=McDonald's finally picks trans-fat-free oil|publisher=NBC News|date=30 January 2007}}{{dead link|date=August 2024|bot=medic}}{{cbignore|bot=medic}}

These reformulations can be partly attributed to 2006 Center for Science in the Public Interest class action complaints, and to New York's restaurant trans fat ban, a massive effort led by Minal Amlani under the guidance of Michael Bloomberg, with companies such as McDonald's stating they would not be selling a unique product just for New York customers but would implement a nationwide or worldwide change.{{Cite press release

|date=10 October 2008

|url=https://www.nbcdfw.com/news/health/chick-fil-a-removes-trans-fats-from-menu/1838534/

|publisher=NBC News

|title=Chick-fil-A Removes Trans Fats from Menu}}{{cite press release|title=Burger King to Use Trans-Fat-Free Oil|last=Sainz|first=Adrian |agency=Associated Press|date=6 July 2006|url=https://phys.org/news102934980.html|access-date=6 July 2007|archive-url=https://web.archive.org/web/20070929121102/http://www.physorg.com/news102934980.html|archive-date=29 September 2007}}[http://www.ihop.com/-/media/ihop/PDFs/nutritionalinformation.ashx Nutrition Information] {{webarchive|url=https://web.archive.org/web/20150721121349/http://www.ihop.com/-/media/ihop/PDFs/nutritionalinformation.ashx |date=21 July 2015}}. Ihop.com (2015). Retrieved 22 August 2015.

• Diet and heart disease
• Health crisis
• Interesterified fat
• Hydrogenated fat
• Margarine

{{notelist}}

{{Reflist|colwidth=30em}}

{{refbegin}}

• {{cite book |editor1-last=Dijkstra |editor1-first=Albert |editor2-last=Hamilton |editor2-first=Richard J. |editor3-last=Wolf |editor3-first=Hamm |title=Trans Fatty Acids |publisher=Blackwell |year=2008 |isbn=978-1-4051-5691-2 }}
• {{cite journal|url=http://members.ift.org/NR/rdonlyres/27B49B9B-EA63-4D73-BAB4-42FEFCD72C68/0/crfsfsv4n1p00220030ms20040577.pdf|vauthors=Jang ES, Jung MY, Min DB|title=Hydrogenation for Low Trans and High Conjugated Fatty Acids|journal=Comprehensive Reviews in Food Science and Food Safety|volume=1|year=2005|archive-url=https://web.archive.org/web/20081217185908/http://members.ift.org/NR/rdonlyres/27B49B9B-EA63-4D73-BAB4-42FEFCD72C68/0/crfsfsv4n1p00220030ms20040577.pdf|archive-date=17 December 2008}}

{{refend}}

{{Wiktionary}}

• [http://www.voicemagazine.org/articles/articledisplay.php?ART=5145 "Ban the Trans: These Sorry Lipids Should Go Away"]
• [http://www.cspinet.org/transfat/ Center for Science in the Public Interest Trans Fat Page]
• [https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/fats-and-cholesterol/types-of-fat/transfats/ Harvard School of Public Health webpage on trans-fat]
• {{cite web|url=https://www.fda.gov/regulatory-information/search-fda-guidance-documents/small-entity-compliance-guide-trans-fatty-acids-nutrition-labeling-nutrient-content-claims-and |title=Labeling & Nutrition – Guidance for Industry: Trans Fatty Acids in Nutrition Labeling, Nutrient Content Claims, Health Claims; Small Entity Compliance Guide |date=August 2003 |publisher=Center for Food Safety and Applied Nutrition |access-date=6 April 2014 |archive-url=https://web.archive.org/web/20131026212809/https://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/LabelingNutrition/ucm053479.htm |archive-date=26 October 2013 |url-status=live }}
• [https://www.fda.gov/OHRMS/DOCKETS/98fr/03-17525.htm Federal Register – 68 FR 41433 11 July 2003: Food Labeling: Trans Fatty Acids in Nutrition Labeling, Nutrient Content Claims, and Health Claims]

{{Lipids}}

{{Vascular diseases}}

{{DEFAULTSORT:Trans Fat}}

Category:Lipids

Category:Nutrition

#

Category:Carboxylic acids

Category:Catalysis

Category:Edible oil chemistry