See Fatty acidsTrans fatty acids are unsaturated fatty acids present in the diet that are derived from ruminant meats or dairy and through conversion of liquid to semisolid or solid fats by the industrial process of partial hydrogenation.
Fat hydrogenation is the process of combining fat, typically, vegetable oils , with hydrogen, in order to make it more saturated.
The process is typically carried out at very high pressure, with the help of a nickel catalyst.
Partial hydrogenation reduces most, but not all, of these carbon-carbon double bonds.
Hydrogenation is controlled by restricting the amount of hydrogen, reaction temperature and time, and the catalyst.
Dietary trans fats are associated with an increase in total and low density lipoprotein cholesterol levels, and an increase risk of cardiovascular disease.
The goal is to turn liquid oils into solid or semi-solid fats that can replace butter and shortening in spreads, candies, baked good, and other products.
Partial hydrogenation of a typical plant oil to a typical component of margarine.
When the C=C double bonds are removed by hydrogenation the melting point is elevated.
Hydrogenation converts liquid vegetable oils into
Solid or semi-solid fats are preferred for baking because the way the fat mixes with flour produces a more desirable texture in the baked product.
Partially hydrogenated vegetable oils are cheaper than animal fats.
Partially hydrogenated vegetable oils are available in a wide range of consistencies, and have other desirable characteristics: increased oxidative stability and longer shelf life, and they are the predominant fats used as shortening in most commercial baked goods.
Full hydrogenation results in a molecule containing the maximum amount of hydrogen.
Trans double bonds induce a linear conformation to the molecule, favoring its rigid packing as in plaque formation, contributing to coronary artery disease.
Full hydrogenation results in the conversion of an unsaturated fatty acid into a saturated one.
Partial hydrogenation results in the addition of hydrogen atoms at some of the empty positions, with a corresponding reduction in the number of double bonds.
Commercial hydrogenation tries to obtain a mixture of fats that is solid at room temperature, but melts during baking, or consumption.
A side effect of incomplete hydrogenization is the isomerization of some of the remaining unsaturated carbon bonds to their trans isomers.
Trans fats that results from partial hydrogenation have been implicated in circulatory diseases including heart disease.
The conversion from cis to trans bonds is chemically favored because the trans configuration has lower energy than the natural cis one.
The food industry has moved away from partially hydrogenated fats, trans fats, and towards fully hydrogenated fats and interesterified fats in response to bad publicity about trans fats, labeling requirements, and removal of trans fats from the FDA list of foods Generally Recognized as Safe.
Complete hydrogenation produce trans fats to give saturated fats.
Replacing trans fats and saturated fats with cis monounsaturated and polyunsaturated fats is beneficial for health.
Consuming trans fats has been shown to increase the risk of coronary artery disease in part by raising levels of low-density lipoprotein (LDL). lowering levels of high-density lipoprotein (HDL), increasing triglycerides in the bloodstream and promoting systemic inflammation.
The primary health risk identified for trans fat consumption is an elevated risk of coronary artery disease (CAD).
On a per-calorie basis, trans fats appear to increase the risk of CAD more than any other macronutrient.
Trans fats confers substantially increased risk of CAD at low levels of consumption at 1 to 3% of total energy intake.
The Nurses’ Health Study – a cohort study that has been following 120,000 female nurses since its inception in 1976, determined that a nurse’s CAD risk roughly doubled for each 2% increase in trans fat calories consumed, instead of carbohydrate calories.
For each 5% increase in saturated fat calories, instead of carbohydrate calories, there was a 17% increase in CAD risk.
Replacing saturated fat or trans unsaturated fat by cis, unhydrogenated, unsaturated fats was associated with larger reductions in risk than an isocaloric replacement by carbohydrates.
Replacing 2% of food energy from trans fat with non-trans unsaturated fats more than halves the risk of CAD (53%).
Another study considered deaths due to CAD, with consumption of trans fats being linked to an increase in mortality, and consumption of polyunsaturated fats being linked to a decrease in mortality.
Trans fat has been found to act like saturated in raising the blood level of LDL but, unlike saturated fat, it also decreases levels of HDL.
Hydrogenation of fats allows margarine, unlike butter, to be taken out of a refrigerator and immediately spread on bread.
Hydrogenated fat provides superior baking properties compared to lard.
Hydrogenated fats can replace butter and lard in baking bread, pies, cookies, and cakes.
Its primary health risk identified for trans fat consumption is an elevated risk of coronary artery disease (CAD).
On a per-calorie basis, trans fats appear to increase the risk of CAD more than any other macronutrient, conferring substantially increased risk of CAD at low levels of consumption at 1 to 3% of total energy intake.
Transfats in human breast milk fluctuate with maternal consumption of transfat, and that the amount of trans fats in the bloodstream of breastfed infants fluctuates with the amounts found in their milk.
A study found a strong relation between dietary trans fat acids and self-reported behavioral aggression and irritability, suggesting but not establishing causality.
Trans fatty acid consumption is linked to worse word memory in adults during years of high productivity, adults age <45.
Trans fats are one of several components of Western diets which promote acne, along with carbohydrates with high glycemic load such as refined sugars or refined starches, milk and dairy products, and saturated fats, while omega-3 fatty acids, which reduce acne, are deficient in Western diets.
Intake of dietary trans fat perturbs the body’s ability to metabolize essential fatty acids (EFAs, including Omega-3) leading to changes in the phospholipid fatty acid composition of the arterial walls, thereby raising risk of coronary artery disease.
US food companies were required to removed partially hydrogenated oils from products by 2018 decreasing industrial trans fat content in the food supply.