Trans Fat

Trans fat is the common name for unsaturated fat with trans-isomer (E-isomer) fatty acid(s). Because the term refers to the configuration of a double carbon-carbon bond, trans fats are sometimes monounsaturated or polyunsaturated, but never saturated. Trans fats do exist in nature but also occur during the processing of polyunsaturated fatty acids in food production.

The consumption of trans fats increases the risk of coronary heart disease by raising levels of LDL cholesterol and lowering levels of "good" HDL cholesterol. There is an ongoing debate about a possible differentiation between trans fats of natural origin and trans fats of vegetable origin but so far no scientific consensus was found. Two Canadian studies, that received funding by the Alberta Livestock and Meat Agency and the Dairy Farmers of Canada, have shown that the natural trans fat vaccenic acid, found in beef and dairy products, may have an opposite health effect and could actually be beneficial compared to hydrogenated vegetable shortening, or a mixture of pork lard and soy fat, e.g. lowering total and LDL cholesterol and triglyceride levels. In lack of recognized evidence and scientific agreement, nutritional authorities consider all trans fats as equally harmful for health and recommend that consumption of trans fats be reduced to trace amounts.

Unsaturated fat is a fat molecule containing one or more double bonds between the carbon atoms. Since the carbons are double-bonded to each other, there are fewer bonds connected to hydrogen, so there are fewer hydrogen atoms, hence the name, 'unsaturated'. Cis and trans are terms that refer to the arrangement of the two hydrogen atoms bonded to the carbon atoms involved in a double bond. In the cis arrangement, the hydrogens are on the same side of the double bond. In the trans arrangement, the hydrogens are on opposite sides of the double bond.

The process of hydrogenation adds hydrogen atoms to unsaturated fats, eliminating double bonds and making them into partially or completely saturated fats. However, partial hydrogenation, if it is chemical rather than enzymatic, converts a part of cis-isomers into trans-unsaturated fats instead of hydrogenating them completely. Trans fats also occur naturally in a limited number of cases: Vaccenyl and conjugated linoleyl (CLA) containing trans fats occur naturally in trace amounts in meat and dairy products from ruminants, although the latter also constitutes a cis fat.