Foods Rich in Trans Fatty Acids


Trans fatty acids (TFA) are unwanted lipid molecules because they are recognized as harmful.

They are naturally present in some foods (especially milk, derivatives and some meats), but in absolutely reduced concentrations compared to those of industrial products containing hydrogenated fats. Moreover, some studies differentiate the health risks of those obtained industrially or transformed by cooking, from those naturally present in food (for example vaccenic acid); the latter would be harmless or even beneficial to health.

Hydrogenation Process

Without dwelling on the topic (which has already been extensively covered in the various dedicated articles), let's try to give an understandable meaning to the term “hydrogenated fat”: it is an unsaturated lipid (with one or more double bonds, therefore initially of a liquid consistency) artificially saturated (breaking the double bonds by adding the missing hydrogens, therefore transformed into a solid) through a chemical-physical process called hydrogenation; this artifact is performed at the request of the food industries which, based on the needs of the various preparations (brioches, breadsticks, etc.) choose the specific consistency of the hydrogenated fat (there are different levels of hydrogenation).

Use: there are many hydrogenated fats and they differ from each other by various characteristics: starting fatty acids, saturation level (one, two or more hydrogenated double bonds), concentration of trans fatty acids (obtained involuntarily from hydrogenation) etc.

To know more:
Hydrogenated fats

Trans Fatty Acids

In organic chemistry a fatty acid is defined trans when, from a “geometrical” point of view, the hydrogen (H) normally bonded to a carbon (C) is placed in a direction mirror opposite to the cis form. Apparently the molecule does not change, except for a small detail, well, this very little detail makes a trans fat a potentially harmful element.

They are quite common trans fatty acids: myristelaidic acid, palmitelaidic acid, petroselaidic acid, elaidic acid, vaccenic acid, cetelaidic acid, brassidic acid and linolelaidic acid.

Food Sources

Trans fatty acids are present mainly in hydrogenated fats, therefore in foods that contain margarines or in those fried in semi-hydrogenated oils/fats; but not only. Even simple excessive thermal exposure favors the cis/trans mutation, as occurs for example during excessive frying and/or exceeding the smoke point; furthermore, following peroxidation and rancidity (due to bacteria, light, oxygen, high temperatures, etc.) a further increase in these unwanted molecules is observable.

However, there are also many natural foods that themselves contain trans fatty acids; this is the case of dairy products and meat obtained from the slaughter of some animals. This phenomenon is linked to the gastrointestinal physiology of ruminants which, during the digestive process, undergo bacterial fermentation of the digestive contents; during this process, microorganisms determine the conversion of some cis fatty acids into trans fatty acids which are then absorbed at the intestinal level, secreted in milk and/or accumulated in meat. Let's be clear, we are talking about concentrations that range from 1/7 to 1/30 of those referring to margarines, therefore (in my opinion) hardly relevant, even if worthy of note.

The foods that contain the greatest amount of trans fatty acids are: margarines, brioches, sweet snacks, pretzels, frozen French fries, donuts, butter, stock cubes, soup mixes, fast food, frozen fish in breadcrumbs, bagged popcorn, mature cheeses, etc.

Side Effects and Dangers

According to the most important international research institutes, there is no quantity of trans fats that our body can tolerate without experiencing negative effects.

Eating mainly, or even frequently, foods rich in trans fats is harmful to your health. Not only that, the consumption of hydrogenated or partially hydrogenated oils, even just a small percentage in the daily diet, is sufficient to create alterations in the body.

The substantial problem that our organism shows towards these fatty acids probably consists in the fact that it does not possess the specific enzyme (lipase) to regulate their metabolic transformation.

Trans fatty acids are linked by numerous scientific studies to: alterations in lipid and glucose metabolism, changes in the functionality of the cell membranes of neurons (nervous system cells), obesity, carcinogenesis, hormonal and fertility problems.

A diet characterized by foods rich in trans fats is mainly correlated with excessive weight, an increased risk of hypercholesterolemia and diabetes, therefore vascular diseases (atherosclerosis and stroke), and nervous degeneration such as Alzheimer's disease.

More specifically, trans fatty acids:

  • they worsen the transport of fats in the blood by lipoproteins; they determine a reduction in cholesterol transporters from the periphery to the liver (HDL) and increase cholesterol carriers from the liver to the periphery (LDL). In the long term, this unwanted mechanism can determine the accumulation of oxidized LDL within the vascular walls and subsequently (also thanks to inflammatory processes) the formation of atherosclerotic plaques with an increased risk of mortality (atherosclerosis).

Use: In the USA alone, trans fats are estimated to be implicated in the deaths of several tens of thousands of people per year from coronary heart disease and cancer. However, it is difficult to correlate a disease of multiple etiology with a single factor, which is why these numbers could be lower or even higher.

  • they worsen cellular efficiency and functionality, interfering in the liquid mosaic of cellular membranes and causing a relative “stiffening” with consequent limitation of the potential for energy production, absorption and communication with other cells. Furthermore, trans fatty acids enter into competition with the essentials in the constitution of cell membranes; even a significant intake of omega 3 and omega 6 can therefore be nullified by an overall incorrect diet.
  • they also negatively affect the integrity of the central nervous system; the brain of a person who frequently eats trans fats ages more quickly, is more predisposed to degenerative diseases such as senile dementia and reacts badly to depressive disorders”.

Use: from 12/13/2014 the expression “totally or partially hydrogenated”, depending on the case, must appear on the label if the oils or fats present in the food product have been hydrogenated. It is also mandatory to specify the specific vegetal origin of the oils that make up the blend of vegetable fats (e.g. palm oil, coconut oil, etc.).

Safety Limit

The World Health Organization and the Food and Agriculture Organization of the United Nations recommend reducing trans fat intake to below 1% of total calories. The European Food Safety Authority (EFSA) suggests taking as little as possible.


  • Manual of oils and fats – P. Capella, E. Fedeli, G. Bonaga, G. Lerker – New techniques –12.3
  • Clinical nutrition manual – R. Mattei – Maedi-Care – pages 37-38


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