Fried food, fast food, pastries, ready meals: beware of trans fats

Unsaturated fatty acids that can be produced by natural or food technology processes - that sounds fairly harmless at first. But in January 2023, Dr Tedros Adhanom Ghebreyesus had very clear words for these so-called trans fats or trans fatty acids. "Trans fats are toxic substances that kill and have no place in food," said the head of the World Health Organisation (WHO). They are responsible for the premature death of half a million people worldwide every year.

What are trans fatty acids?

Many of your foods contain trans fats: natural and/or artificial. The former are formed in the digestive tract of some animals, by microorganisms that are found in the rumen of cattle, for example, where they process fatty acids from the feed. If food is then obtained from these animals, such as milk or meat, it may contain natural trans fats. The quantities vary greatly depending on the feed, husbandry and animal species.

The second type, artificial trans fats or trans fatty acids, are usually created during industrial processing, in which hydrogen is added to liquid vegetable or fish oils at room temperature. The process is called hydrogenation. "This changes the stability and texture of oils," writes the food industry initiative "Österreich isst informiert".

The oils are technically hardened in order to obtain favourable spreadable fat products that are easy to use in further food production and have a long shelf life. They also give products the desired flavour and consistency.

In addition to hydrogenation, artificial trans fatty acids from the German Society for Nutrition (DGE), artificial trans fatty acids can also be produced during the thermal treatment of vegetable oils - for example, through strong or repeated heating when cooking, frying or deep-frying in oil. This happens not only in restaurants and fast food chains, but also at home on the cooker.

Risky substance: artificial trans fats

"Whether trans fatty acids from natural sources are just as harmful as those from processed oils is scientifically controversial," says Dagmar von Cramm, nutrition expert from the German professional association for ecotrophology.

However, there is consensus on the major problem with industrial trans fatty acids: unlike other fatty acids, they have no positive properties whatsoever. On the contrary.

It has long been known that a high intake of trans fatty acids has a detrimental effect on health. Consumption is particularly dangerous for overweight people and diabetics and with increasing age.

The risk of heart attacks and strokes increases, as can be read in the MSD Manual (an international handbook for medicine). In addition, trans fatty acids can promote inflammatory processes and are even associated with faster brain ageing and poorer cognitive performance. A study with rats showed as early as 2005: Trans fatty acids affected the animals' brains.

Not sufficient protection for the world's population

This is why the US Food and Drug Administration (FDA) made an important finding back in November 2013: Partially hydrogenated oils from industry in food are no longer recognised as generally safe. But even ten years later, harmful trans fatty acids are still found in many foods.

At the beginning of the year, the WHO, which had actually wanted trans fats to disappear from food chains by 2023, had to draw a less than favourable balance: From Australia to Pakistan, currently 9 of the 16 countries with the highest estimated proportion of coronary heart disease deaths attributable to trans fat intake have no best practice strategy to curb the health threat. Overall, more than five billion people worldwide are still not adequately protected from trans fatty acids, which are harmful to health.

Leading by example

The example of Denmark shows that restricting industrial trans fats can actually have a positive impact on people's health. Trans fatty acids were drastically restricted there 20 years ago. According to the WHO, this led to a significant reduction in cardiovascular diseases. According to a study, the number of deaths from coronary diseases also fell by around 700 per year.

The rest of the EU lagged behind for a long time, but followed suit in 2021: since then, only foods containing less than two grams of industrial trans fats per 100 grams of fat have been allowed on the market. In other words, the proportion of trans fatty acids of non-natural origin may not exceed two per cent of the total fat.

And the maximum limit requirements appear to be working: For example, checks carried out by the Lebensmittel- und Veterinärinstitut Braunschweig/Hannover two years ago found only one in 100 samples from the baked goods sector that exceeded the limit. The average content was 0.74 grams per 100 grams of fat. "Compared to previous tests, the levels have reduced significantly," writes the Lower Saxony State Office for Consumer Protection and Food Safety.

In Switzerland, the content of trans fatty acids has also been limited by law - to two per cent of the total fat content, according to a communication from the Federal Council from 2017.

No problem at all?

So everything is fine with trans fatty acids in our part of the world? Not quite. Because they are still contained in many foods and bags that you consume. And even if manufacturers (have to) adhere to the guidelines, the recommended maximum amounts are often quickly exceeded.

All in all, the DGE recommends: "According to the D-A-CH reference values for nutrient intake, the intake of trans fatty acids should account for less than one per cent of food energy." With a daily energy intake of 2,000 kilocalories, this is a maximum of 2.2 grams. And 2.2 grams is not a lot when you consider that even a single croissant can contain up to 1 gram, and a doughnut even up to 2 grams.

Because the substances are found in fried foods, fast food, pastries and ready meals in particular and make these foods particularly crispy and tasty, young people in particular run the risk of consuming too much of them. "Young men in particular belong to the risk group," says nutrition expert Dagmar von Cramm. A burger here, a handful of crisps there: It quickly adds up to an attack on your health. An article in the New England Journal of Medicine warned that just five grams a day increases the risk of cardiovascular disease by 25 per cent.

A balanced diet protects

On average, however, the problem no longer appears to be serious in society. According to a calculation by the German Federal Institute for Risk Assessment, the average level of trans fatty acids consumed in Germany was 0.66 per cent of dietary energy, i.e. below the recommended 1 per cent.

The aforementioned communication from the Swiss Federal Council also contained the results of a nutritional study by Agroscope and the Inselspital Bern, which investigated the effect of natural and industrial trans fatty acids on the risk of cardiovascular disease.

According to the study, the quantities of trans fatty acids consumed in Switzerland today do not pose a health problem, regardless of their origin. For heart-healthy consumers, this means that there is no risk from trans fatty acids if they follow the Swiss dietary recommendations.

Avoid trans fatty acids

A balanced diet offers protection above all. This also includes reducing the consumption of foods that are rich in trans fatty acids. According to the DGE, in addition to pastries made from puff pastry, pizza and confectionery, these are mainly fried (potato) products such as crisps or chips and high-fat ready meals as well as biscuits and nut and nougat creams.

When shopping, you can make sure that not too many trans fatty acids end up in your shopping basket. You can recognise the bad fats by looking for information such as "hydrogenated" or "partially hydrogenated oil" on the ingredients list. In ready meals, trans fatty acids are also listed as "vegetable fat, partially hydrogenated" or "unsaturated fatty acids, contains hydrogenated fats" or as "hydrogenated vegetable fat".

Even in the home kitchen, make sure you only use suitable oils, such as refined, heat-stable vegetable oils like corn oil, sunflower oil, peanut oil, soya oil and rapeseed oil. Lard, coconut oil and ghee, i.e. clarified butter, are also good for high heat. Important: Do not reuse the fat or oil too often and do not heat it too high. This is because cooking, frying and deep-frying change the molecular structures of the fat. Vegetable oils with a high content of unsaturated fatty acids can be converted into trans fatty acids at temperatures as low as 130 degrees.