Trans fatty acids are unsaturated fatty acids that have at least one double bond in trans configuration. While trans fatty acids occur in nature only in small quantities in ruminants, they are formed in larger quantities mainly during fat hardening in the food industry. Consumption of trans fatty acids above a certain percentage level leads to an increase in LDL cholesterol and a decrease in HDL cholesterol, with all the associated health risks such as atherosclerosis and coronary heart disease.
What are trans fatty acids?
Saturated fatty acids are carboxylic acids with hydrocarbon chains of varying lengths – usually unbranched. Their molecular formula is CnH2n+1COOH. If there are one or more double bonds between two carbon atoms, the fatty acid is monounsaturated or polyunsaturated. In the case of unsaturated fatty acids, a so-called cis-trans configuration isomerism exists. A cis- or Z-isomerism exists when both carbon atoms with a double bond have their substituents on the same side. In trans or E isomerism, the two substituents are on opposite sides. Although the chemical formula for both isomers does not change, the two forms differ considerably in their physical and biochemical properties. Their effects within the metabolism also differ considerably. Naturally occurring unsaturated fatty acids occur almost exclusively in the cis form. Only in the rumen of ruminants do anaerobic bacteria produce unsaturated fatty acids in the trans configuration, so that milk from ruminants and cheese made from it also contain small amounts of trans fatty acids. Natural vegetable fats and oils consist exclusively of fatty acids in the cis form, which is important for metabolism. Trans fatty acids, also known simply as trans fats, are produced on a large scale during the industrial processing of foods, especially during fat hardening to achieve a certain consistency. The proportion of trans fatty acids is alarmingly high in many deep-fried potato products (French fries, potato chips), in convenience foods and in certain industrially produced baked goods, as well as in some nut-nougat creams. Even on the home stove, harmful trans isomers can form from valuable cis-vegetable oils when heated to over 130 degrees Celsius as is the case when polyunsaturated vegetable oils are used for frying.
Increased risk of stroke as a result
Trans fats are considered to have an impact on cholesterol metabolism. Trans fats in the diet lead to an increase in the LDL (low density lipoprotein) fraction with a simultaneous decrease in the HDL (high density lipoprotein) fraction within the total cholesterol fraction. Since cholesterol is essential for the structure of all cell membranes and for the synthesis of steroid hormones, but is also virtually insoluble in water, it requires transport agents known as lipoproteins. In gross simplification of the metabolic processes involved, it can be stated that LDLs in the blood transport the cholesterol to the membranes of the cells, while HDLs take over the return transport of unneeded cholesterol to the liver. This has led to LDL being colloquially referred to as “bad” cholesterol and HDL as “good” cholesterol. An imbalance in the ratio between HDL and LDL in favor of the LDL fraction leads to an excess of cholesterol in the membranes of arterial blood vessels, especially in the coronary arteries, thus promoting the formation of atherosclerosis. Triggered by arteriosclerotic changes in the arterial vessel walls, constrictions (stenoses) or even blockages of the arteries develop. Conglomerates of erythrocytes (thrombi) can also form at the narrow points, triggering a stroke if they are carried with the bloodstream to the brain, where they cause an arterial blockage. If the proportion of trans fats ingested exceeds one percent of the daily energy intake required as an energy source, the risk of stroke and the risk of suffering coronary heart disease increase dramatically.
Beware of hidden trans fatty acids
In the U.S., the health problems that eating foods containing artificial trans fats can cause have already led to consequences at the Food and Drug Administration (FDA). In European countries, there are still no uniform regulations governing the content of trans fats in food. At present, there are still isolated national regulations, such as those in Austria and Denmark, which restrict the permissible levels of trans fatty acids in certain foods. Corresponding EU directives, which must be implemented by all EU member countries, are in preparation. The issue has also been present in Europe since 1999, when the FDA published an extensive study on the content of trans fats in foods. The only indication German consumers receive about the presence of trans fats in a particular product is merely the mandatory declaration “contains hydrogenated fats.” Ultimately, this means that there is still no target-oriented mandatory declaration of the proportion of trans fats in products. At present, it can still be assumed that industrially manufactured convenience products such as French fries, chips of all kinds, fast food products and some baked goods contain trans fatty acids in questionable quantities. Whenever “hydrogenated” or “partially hydrogenated” fats play a role in the manufacture of the products, caution is advised. In the manufacture of finished products, the industry relies on “hardening” unsaturated fatty acids by hydrogenation using high temperatures of up to 200 degrees and pressure, or giving the fatty acids the desired and necessary consistency. The aim is to produce saturated fatty acids from unsaturated fatty acids. Because the process is not complete, unsaturated fatty acids in trans configuration are also produced as undesirable by-products. For this reason, restraint is generally advised when using artificially produced spreads and also spreads.
Why an “oil change” makes sense
Trans fatty acids from industrial production are a problem because they are not classified as foreign by the body’s metabolism. Instead, they are further processed like natural cis fatty acids and incorporated into body substances without showing the expected metabolic reactions there. Also, the effect of trans fats on increasing LDL concentration while decreasing the HDL fraction gives reason to substitute foods containing more than two percent trans fatty acids in their total fat content with foods containing natural unsaturated fatty acids in cis configuration, i.e., to perform an “oil change” in these cases. It is very likely that in a few years’ time EU member states will impose rigorous restrictions on the permitted proportion of trans fatty acids in foods, following the example of the USA. A natural proportion of trans fatty acids occurs, for example, in dairy products from ruminants. These are almost exclusively conjugated linoleic acids, in which the two double bonds are always found on two adjacent carbon atoms. There is controversy among experts as to whether conjugated linoleic acid, which always occurs in trans configuration, has a positive health effect in contrast to artificial trans fats. Studies to date do not necessarily support this conclusion; however, no negative health effects have been demonstrated to date either.
Prefer to prepare your own
A safe alternative to convenience foods, ready-to-eat pizzas, French fries, which are “blessed” with a fair amount of trans fats, is offered by home-prepared meals, which should consist exclusively of natural ingredients. They not only protect against the unwanted consumption of trans fats with all the associated health risks, but also ensure a natural taste experience. Consumption of animal products derived from ruminants contains conjugated linoleic acid, a naturally occurring unsaturated fatty acid in trans form. According to current knowledge, conjugated linoleic acid is not associated with health risks, but it also shows no demonstrable positive effects.
