Fatty acids are part of fats and oils. They are basically chains of carbon atoms bonded to hydrogen atoms. They differ in length and shape of the carbon chain as well as the number of double bonds between carbon atoms and the number of hydrogen atoms bound to the carbon atoms. Unsaturated fatty acids in contrast to saturated fatty acids have at least one carbon-to-carbon double bond. Most unsaturated fatty acids are slightly bent at their double bond and are in their so-called cis-configuration. Due to this structure vegetable fats, high in unsaturated fats, e.g. olive oil, are naturally liquid at room temperature. Fatty acids in trans-configuration also have a carbon-to-carbon double bond. Their structure slightly differs in that they are not bent at their double bond and are therefore solid at room temperature.
3D-structure of fatty acids. white: hydrogen atoms, black: carbon atoms bound with a single bond, blue: carbon atoms bound with a double bond. A) saturated fatty acid, b) unsaturated fatty acid in cis-configuration, c) unsaturated fatty acid in trans-configuration (1)
TFA occur naturally in stomachs of ruminant animals and therefore small amounts can be found in cows, goats and sheep milk and meat. The main source of TFA, however, is industrially produced partially hydrogenated oil: Vegetable oils are modified, some of the cis– are converted into trans-fatty acids which hardens the vegetable fats. In the past, these partially hydrogenated oils have been widely used in products like margarine, baked goods, frying fat for industrial use and soup and sauce powders due to economic and also technological advantages. Partially hydrogenated oils have an increased shelf life and are more resistant to repeated heating. They enhance the texture of baked goods. Combinations of oils and partially hydrogenated oils help to achieve semi-solid, spreadable textures e.g. in margarine. Cooking at high temperatures can also trigger the conversion from cis to trans-fatty acids at the consumer level, e.g. homemade deep-fried chips or chicken nuggets. Another rather unknown source of TFAs are mono‐ and diglycerides of fatty acids (E 471) and their salts (E 470a and E 470b). These food additives are widely used as emulsifiers in the food and beverage industry and their TFA content is currently not regulated. A very recent EFSA statement recommended revising the specification of mono-and diglycerides including a maximum limit for TFA.
As opposed to some essential unsaturated cis-configured fatty acids, there is no requirement in the human body for trans-fatty acids. A number of intervention studies show that TFAs are linked to adverse health effects namely an increase of LDL cholesterol and a decrease of HDL-Cholesterol (2). A dose-dependent linear effect of TFA intake and the risk of cardiovascular disease was established and furthermore confirmed in prospective cohort studies. It was estimated that approximately 540,000 deaths worldwide were caused by excess TFA intake in 2010 (3).
Apart from a limitation of TFA in infant formulae, there are no EU-regulations currently regarding the TFA content in foods nor is there a specific requirement for labelling TFA in food products. However, some countries have taken the initiative: in 2003, being the first European country, Denmark introduced a legal limit of TFA in oils and fats of <2%. To date, seven European countries have a national legal limit on TFA in foods. National recommendations for TFA intakes are between <1 and <2% of total energy intake. Some countries e.g. Belgium, Germany, Austria, Nordic countries, Spain and Italy have recently updated their intake recommendations to be as low as possible. In the US, since 2015 the FDA is not recognising partially hydrogenated oils as generally safe anymore and pushed for partially hydrogenated oils to be removed by food manufacturers by June 2018. Labelling trans fatty acids on food products has been mandatory in the US since 2006.
With a newly released action package called REPLACE, the WHO now aims to bring down the dietary intake of TFA to less than 1% of total energy intake worldwide. They have called on governments, especially those where no actions are set in place yet, to fully eliminate and replace industrially produced trans-fatty acids from the food supply by 2023 (4).
In the mid-1990’s the mean intake of TFA in EU countries ranged between 1.2 and 6.7 g per day (5). More recent assessments show that the average TFA intake was decreased considerably since and is on average below 1% of the total energy intake (6). Certain subpopulations are however still exceeding the WHO recommendation of <1% of total energy intake, namely adults aged 18-30 from Croatia and Spain as well as low-income citizens in the UK (based on consumption data from 2003-2005). Despite several voluntary reformulations in the food industry some foods are still found to contain high amounts of TFA (up to 50% of the fat content in products) e.g. popcorn, biscuits, wafers and cakes mainly in Eastern and South Eastern European countries (7).
After the setting of a legal limit of TFA in Denmark, the average content of TFA in foods dropped remarkably and the number of deaths caused by cardiovascular disease declined significantly showing the effectiveness of their policy (8). Given the clear evidence of negative health effects of the intake of TFA all over the world, recent developments and updated statements by national and international governments and organisations are going towards the elimination of industrial TFA. It is therefore only a matter of time that the EU will have to legally limit industrial content of TFA in products as well. EU member states have already voted for an EU-commission proposal towards a TFA limit in industrially produced foods. The regulation is planned to be adopted by spring this year (9).
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