Trans fats, or trans-unsaturated fatty acids, trans fatty acids, are a type of unsaturated fat that occur in small amounts in nature but became widely 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, a leading cause of death in Western nations.
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 (often referred to as "bad cholesterol"), lowering levels of the lipoprotein HDL (often referred to as "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 of trans fats be reduced to trace amounts.
| Trans (Elaidic acid) |
Cis (Oleic acid) |
Saturated (Stearic acid) |
| Elaidic acid is the principal trans unsaturated fatty acid often found in partially hydrogenated vegetable oils. |
Oleic acid is a cis unsaturated fatty acid making up 55–80% of olive oil. |
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. |
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| These fatty acids are geometric isomers (structurally identical except for the arrangement of the double bond). |
This fatty acid contains no carbon-carbon double bonds and is not isomeric with the previous two. |
Trans fat contents in various foods, ranked in g per 100 g
| food type |
trans fat content |
| shortenings |
10 to 33 g |
| margarine/spreads |
0.2 to 26 g |
| butter |
2 to 7 g |
| whole milk |
0.07 to 0.1 g |
| breads/cake products |
0.1 to 10 g |
| cookies and crackers |
1 to 8 g |
| salty snacks |
0 to 4 g |
| cake frostings and sweets |
0.1 to 7 g |
| animal fat |
0 to 5 g |
| ground beef |
1 g |
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