Trans fat
From Free net encyclopedia
A trans fatty acid (commonly shortened to trans fat) is an unsaturated fatty acid whose molecules contain trans double bonds between carbon atoms, which makes the molecules less kinked compared with those of 'cis fat'. Research suggests a correlation between diets high in trans fats and diseases like atherosclerosis and coronary heart disease. The US National Academy of Sciences recommended in 2002 that dietary intake of trans fatty acids should be totally eliminated.
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History
Hydrogenation of edible oils was invented by the German chemist Wilhelm Normann, who patented the process in 1902. In 1909 Procter & Gamble in Cincinnati acquired the US rights to the Normann patent and in 1911 they began marketing Crisco, the first hydrogenated shortening, which contained a large amount of partially hydrogenated cottonseed oil. Further success came from the marketing technique of giving away free cookbooks with every recipe calling for Crisco. Hydrogenation strongly stimulated whaling, as it made it possible to stabilize whale oil for human consumption.
Ironically, public campaigns against saturated fat have caused increased consumption of trans fat. The Center for Science in the Public Interest (CSPI) campaigned against fast foods using saturated fats starting in 1984. When fast food companies replaced the saturated fat with trans fat, CSPI's campaign against them ended. CSPI defended trans fats in their 1987 Nutrition Action newsletter. By 1992 CSPI began to speak against trans fats and is currently strongly against their use.[1]
Food presence
The majority of trans fats are formed during the manufacture of processed foods (see below for details). In unprocessed foods, most unsaturated bonds in fatty acids are in the cis configuration.
Though some trans fats are found naturally — primarily in dairy products, some meat, and other animal-based foods (in the milk and body fat of ruminants such as cows and sheep), such as conjugated linoleic acid or CLA. These conjugated systems with trans linkages are not counted as trans fat for the purposes of nutritional regulations and labeling in the United States. As a complication, note that some researchers claim that these naturally occurring fats are "good" trans fatty acids. Often, these are nutritionally categorized as saturated fats, categorizing trans fats as just fats that have undergone the hydrogenation process.
Trans fat from partially hydrogenated vegetable oils has displaced natural solid fats and liquid oils in many areas, especially in the fast food industry.
Partial hydrogenation increases the shelf life and flavor stability of foods containing trans fats. These benefits for food manufacturers come at a high cost to the consumer's health. Rather than preventing the sale of trans fats, as advocated by consumer advocacy groups, the FDA in the US, as of January 2006, requires that the quantity of trans fat be listed on nutrition labels. These labeling requirements do not apply to restaurants. A benefit of trans fats for food manufacturers is the ability to design trans fat content so that fat will melt at body temperature, but not at room temperature. Partial hydrogenation raises the melting point of the fat, producing a semi-solid material, which is much more desirable than liquid oils for use in baking. Partially hydrogenated vegetable oils are much less expensive than the fats traditionally favored by bakers, such as butter or lard.
In the US, snack foods, fried foods, baked goods, and other processed foods are likely to contain trans fats, as are vegetable shortenings and margarines. Laboratory analysis can determine the amount of fat contained in a product. Outside the US, trans fats have been largely phased out of retail margarines and shortenings. US food manufacturers are now also phasing out trans fats, but at present, most US margarines still have more trans fat than butter. In the 1950s, advocates said that the trans fats of margarine were healthier than the saturated fats of butter, but this has been proven incorrect. See the saturated fats page for details. One example of the effects of trans fats vs saturated fats came from the "Walter Willett Nurses Study" (Professor of Medicine, Harvard Medical School). The 14-year study of 80,082 women who were 34 to 59 years of age concluded that a 2% increase in trans fats, compared to the same increase in carbohydrates, increased a woman's risk of heart disease by 19.3%, while the same study found that a 5% increase in saturated fats increased heart disease risk by 17% compared with the same increase in carbohydrates. [2]
Chemistry
Trans fatty acids are made when manufacturers add hydrogen to vegetable oil, in the presence of small amounts of catalyst metals such as nickel, palladium, platinum or cobalt -- in a process described as partial hydrogenation. If the hydrogenation process were allowed to go to completion, there would be no trans fatty acids left, but the resulting material would be too solid for practical use. A claimed exception to this is The J.M. Smucker Company's new trans fat free Crisco which contains the wax-like fully hydrogenated cottonseed oil blended with liquid vegetable oils to yield a shortening much like the previous Crisco which was made from partially hydrogenated vegetable oil. In a natural fatty acid, the hydrogen atoms are usually on the same side of the double bonds of the carbon chain. However, partial hydrogenation reconfigures most of the double bonds that do not become chemically saturated, so that the hydrogen atoms end up on different sides of the chain. This type of configuration is called trans (which means "across" in Latin). The structure of a trans unsaturated chemical bond is shown in the diagram.
Increasing the pressure at which an oil is hydrogenated reduces trans fat formation. Researchers at the United States Department of Agriculture applied 1400 kPa (200 psi) of pressure to soybean oil in a 2-litre vessel while heating it to between 140°C and 170°C. In a standard 140 kPa (20 psi) process of hydrogenation, the result is about 39.7% trans fat by weight compared to 16.6 to 17.9% using the high pressure method.
Blended with pure soybean oil, the high pressure processed oil produced margarine containing 5 to 6% trans fat which could qualify for a label of zero grams of trans fat. (Eller, et al., 2005)
Biochemistry
Although synthetically created trans fatty acids have been a significant part of the human diet for just over 100 years, the biochemistry of trans fatty acids is poorly understood. Little is known about how trans fatty acids are incorporated into the developing fetal brain tissue, cell membranes, and arterial plaque. Some clinical studies suggest a possible association of trans fatty acids with obesity, metabolic syndrome and diabetes. It is unclear whether the naturally present trans fatty acids in beef, mutton and dairy products (created through fermentation processes in the stomach of ruminant animals) pose the same risks.
Human metabolism requires some essential fatty acids which are destroyed by the hydrogenation process. This may be a particular concern with omega-3 fatty acids, which are thought to be in short supply in the typical Western diet.
The destruction of some of the essential fatty acids is one of the intended goals of hydrogenation, since reducing the proportion of unsaturated fatty acids which are at risk of oxidation creates shortening that is less likely to turn rancid. For example, a typical candy bar might have a shelf life of 30 days without use of hydrogenated oils, while the same product with hydrogenated oils can last up to 18 months.
Trans fat behaves like saturated fat by raising the level of low-density lipoprotein in the blood (LDL or "bad cholesterol") which increases the risk of coronary heart disease (CHD). It has the additional effect of decreasing levels of HDL, the "good" lipoprotein which helps remove cholesterol from arteries.
The majority of clinical research reports have suggested that trans fats may be worse for the body than saturated fats; in fact, the 2002 summary statement by the Institute of Medicine on trans fatty acids concluded that there was no safe level of trans fatty acids in the human diet.
A confounding issue may arise from the cooking process itself, in that trans-fats are often associated with high temperature cooking processes which also favor the formation of Advanced Glycation End Products (AGEs) and oxidation products. It appears some of the studies have not controlled for these AGEs and oxidation products. It has been suggested that, "given the prominence of this type of food in the human diet, the deleterious effects of high-fat foods may be in part due to the high content in glycotoxins, above and beyond those due to oxidized fatty acid derivatives." (Koschinsky, 1997) The glycotoxins, as he called them, are more commonly called AGEs.
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. [3]
Grazing animals also have a naturally-occurring trans fatty acid, absorbed from their feed, Conjugated Linoleic Acid (CLA) [4] that may be beneficial to human health.
Public response
United States
In May 2003, 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. This suit was very effective at bringing the trans fat controversy to public attention.
Prior to 2006, consumers in the United States could not easily determine the presence (or quantity) of trans fats in food products. This information could only be inferred by reading the ingredient list on the food label. If the ingredients included the words "shortening," "partially hydrogenated vegetable oil," or "hydrogenated vegetable oil," the food probably contained trans fat. Because ingredients are listed in descending order of predominance, smaller amounts are present when the ingredient is close to the end of the list.
On July 9, 2003, the United States Food and Drug Administration issued a regulation (21 CFR 101.9 (c)(2)(ii)) requiring manufacturers to list trans fatty acids, or trans fat, on the Nutrition Facts panel of foods and some dietary supplements. This new information must appear below the listing of saturated fat content, which was already required. The regulation allows trans fat levels of less than 0.5 grams per serving to be labeled as 0 grams per serving, or trans fat free. (In this case, manufacturers may use the synonyms "free", "without," "no" and "zero" in their packaging claims.) The FDA defines trans fatty acids as containing one or more trans linkages that are not in a conjugated system.
The new labeling rule took effect January 1, 2006. The FDA created a process where companies may petition for an extension that will be reviewed on a case-by-case basis. Extensions will be granted until January 1, 2008. The FDA estimates that by 2009, trans fat labeling will have prevented from 600 to 1,200 cases of coronary heart disease and 250 to 500 deaths each year. This benefit is expected to result from consumers choosing alternative foods lower in trans fatty acids as well as manufacturers reducing the amount of trans fatty acids in their products.
While the FDA regulation was strictly a labeling directive, many food manufacturers used the 2006 deadline as a target date to reduce or eliminate trans fats from their products. This required some experimentation with alternative oils in an attempt to preserve the flavor and "mouth feel" of the food while maximizing shelf life. The solution for some products was a return to the saturated fats and tropical oils abandoned 20 years earlier, when saturated fats were a high-profile health concern. Another solution was the use of new soybean varieties and processing methods, which produce oils with many of the desirable characteristics of hydrogenated oils without requiring hydrogenation.
Some U.S. restaurant chains have also announced plans to reduce or eliminate their use of hydrogenated oils. New York City has asked all its restaurants to eliminate trans fat from their offerings, on a voluntary basis. In May 2005, Tiburon, California became the first city in the world where all restaurants cook with trans fat-free oils.
Denmark
Denmark became the first country to introduce laws strictly regulating the sale of many foods containing trans fats in March 2003, a move which effectively bans partially hydrogenated oils. Naturally present trace amounts of trans fatty acids in dairy and meat products are unaffected by these bills.
Canada
Canada's food regulator, Health Canada, started mandatory Nutrition Facts labels in 2003 (for gradual introduction over several years); from the beginning, they have required the listing of the amount of trans fats in the food described.
In November 2004, an opposition day motion seeking a ban similar to Denmark's was introduced by Pat Martin of the New Democratic Party, and passed through the Canadian House of Commons by an overwhelming 193-73 vote. [5]
United Kingdom
The UK has been slower than Denmark and Canada in acting on this issue. In October 2004, the Food Standards Agency (FSA) has asked for better labelling in the UK. [6] Some companies such as Nestle have voluntarily removed or reduced trans fats from their products.
See also
References
- Template:Cite journal
- Template:Cite web
- {{cite press release
| publisher = Department of Health and Human Services | date = July 9, 2003 | url = http://www.hhs.gov/news/press/2003pres/20030709.html | title = HHS to Require Food Labels to Include Trans Fat Content }}
- {{cite news
| url = http://www.newscientist.com/article.ns?id=mg18424721.900 | title = Fears raised over the safety of trans fats | publisher = New Scientist }}
- {{cite journal
| author=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 | year=2005 | pages=5982-4 | id=PMID 16028984 }}
External links
- Ban Trans Fats
- Trans Fats or Hydrogenated Oil
- United States Food and Drug Administration (July 11, 2003). Trans Fatty Acids in Nutrition Labeling regulation.
- Chemical Structure of Fats and Fatty Acids
- Research on the Safety of Hydrogenated Vegetable Oils
- Tips on following a low trans fat diet
- Know Your Fatsda:Transfedtsyre
de:Transfettsäuren es:Ácido graso trans hu:Transz-zsírsav fi:Transrasvahappo nl:Transvet zh:反式脂肪 zh-min-nan:Tùi-hoán-pêng lâ-sng