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 "unsaturated". Cis and trans are terms that refer to the arrangement of chains of carbon atoms across the double bond. In the cis arrangement, the chains are on the same side of the double bond, resulting in a kink. In the trans arrangement, the chains are on opposite sides of the double bond, and the chain is straight.
The process of hydrogenation adds hydrogen atoms to cis-unsaturated fats, eliminating double bonds and making them into partially or completely saturated fats. However, partial hydrogenation converts a part of cis-isomers into trans-unsaturated fats instead of hydrogenating them completely. Trans fats also occur naturally to a limited extent: 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.
Unlike other dietary fats, trans fats are not essential, and they do not promote good health. The consumption of trans fats increases the risk of coronary heart disease by raising levels of "bad" LDL cholesterol and lowering levels of "good" HDL cholesterol. Health authorities worldwide recommend that consumption of trans fat be reduced to trace amounts. Trans fats from partially hydrogenated oils are more harmful than naturally occurring oils.
Health risks
