Trans fats, or trans-unsaturated fatty acids, trans fatty acids, are a type of unsaturated fats that are uncommon in nature but became commonly produced industrially from vegetable fats for use in margarine, snack food, packaged baked goods and frying fast food starting in the 1950s. Trans fat has been shown to consistently be associated, in an intake-dependent way, with increased risk of coronary heart disease, the worldwide leading cause of death.
Fats contain long hydrocarbon chains, which can either be unsaturated, i.e. have double bonds, or saturated, i.e. have no double bonds. In nature, unsaturated fatty acids generally have cis as opposed to trans configurations. In food production, liquid cis-unsaturated fats such as vegetable oils are hydrogenated to produce saturated fats, which have more desirable physical properties, e.g. they melt at a desirable temperature (30–40 °C). Partial hydrogenation of the unsaturated fat converts some of the cis double bonds into trans double bonds by an isomerization reaction with the catalyst used for the hydrogenation, which yields a trans fat. Although trans fats are edible, consumption of trans fats has shown to increase the risk of coronary heart disease in part by raising levels of the lipoprotein LDL (so-called “bad cholesterol”), lowering levels of the lipoprotein HDL (“good cholesterol”), increasing triglycerides in the bloodstream and promoting systemic inflammation. 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. Most artificial trans fats are chemically different from natural trans fats. Two Canadian studies have shown that the natural trans fat vaccenic acid, found in beef and dairy products, could actually be beneficial compared to hydrogenated vegetable shortening, or a mixture of pork lard and soy fat, by lowering total and LDL and triglyceride levels. A study by the US Department of Agriculture showed that vaccenic acid raises both HDL and LDL cholesterol, whereas industrial trans fats only raise LDL without any beneficial effect on HDL. In light of recognized evidence and scientific agreement, nutritional authorities consider all trans fats as equally harmful for health and recommend that consumption oftrans fats be reduced to trace amounts
Trans (Elaidic Acid)
Elaidic acid is the principal trans unsaturated fatty acid often found in partially hydrogenated vegetable oils.
Cis (Oleic Acid)
Oleic acid is a cis unsaturated fatty acid making up 55–80% of olive oil
Saturated (Stearic Acid)
Stearic acid is a saturated fatty acid found in animal fats and is the intended product in full hydrogenation. Stearic acid is neither cis nor trans because it has no carbon-carbon double bonds.
Presence in food
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. Natural trans fats, 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 atrans-fatty acid.
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.
Partially hydrogenated oils have been used in food for many reasons. Hydrogenation increases product shelf life and decreases refrigeration requirements. Many baked foods require semi-solid fats to suspend solids at room temperature; partially hydrogenated oils have the right consistency to replace animal fats such as butter and lard at lower cost. They are also an inexpensive alternative to other semi-solid oils such as palm oil.
Up to 45% of the total fat in those foods containing artificial trans fats formed by partially hydrogenating plant fats may be transfat. Baking shortenings, in general, contain 30% trans fats compared to their total fats, whereas animal fats from ruminants such as butter contain up to 4%. Margarines not reformulated to reduce trans fats may contain up to 15% trans fat by weight
