Trans fatty acid

Article By:

Holub, Bruce J. Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.

Last reviewed:December 2019

DOI:https://doi.org/10.1036/1097-8542.704370

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• Trans fatty acids, published October 2008:Download PDF Get Adobe Acrobat Reader

An unsaturated fatty acid that contains a trans (rather than a cis) configuration at the unsaturation sites within its chemical structure. Trans fatty acids (TFAs) are a significant health concern because their levels in diets have increased markedly in many countries. This has led to a ban of artificial (industrially produced) TFAs in foods in the United States and numerous European countries, including Denmark, Norway, Switzerland, Austria, Iceland, and Hungary. Unlike naturally occurring monounsaturated (monounsaturates) and polyunsaturated fatty acids (polyunsaturates) as found in many liquid nonhydrogenated vegetable oils, which have cis double bonds at their unsaturation sites, TFAs have trans double bonds at the unsaturation sites within their structure. [Unsaturated acids can be converted to saturated acids by the addition of hydrogen. Hydrogenation is the chemical binding of hydrogen to the double bonds of unsaturated fatty acids, carried out in the presence of hydrogen, pressure, and typically nickel as a metal catalyst. In cis bonds, adjacent carbons are on the same side of the molecule; in trans bonds, they are on opposite sides (see illustration).] Whereas "natural" monounsaturates and polyunsaturates have curvilinear structures and are liquid at room temperatures, the "industrial" TFAs are typically linear structures that are solid fats at room temperatures due to their much higher melting points. Thus, TFAs approach saturated fats in many of their physical-chemical properties. See also: Fat and oil; Fat and oil (food); Food; Food engineering; Food manufacturing; Hydrogenation

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