A Guide To Trans Fats

Updated: Jan 28

No other constituent of food has been vilified in recent times more than trans fats. Trans fats have been linked to an array of illnesses and diseases, and in countries such as the USA, their use in food manufacturing has been banned. What exactly are trans fats though?

Trans fats are either naturally occurring or, more commonly, manufactured from unsaturated fats. Fats contain long hydrocarbon chains which are either unsaturated (contain a double bond) or saturated (contain no double bonds). The prefix trans- refers to the orientation of the double bond in unsaturated fats where the carbon chain extends from the same side of the double bond, leaving a straighter molecule, and in a cis- orientation - more commonly found in nature - the carbon chain extends from the opposite side of the double bond, leaving a bent molecule.

In nature, trans fats are produced by ruminant animals via a process of biohydrogenation of plant fats performed by bacteria in the animal’s gut. This is a natural process catalysed by bacterial enzymes (1). Humans also produce a type of trans fat - conjugated linoleic acid (CLA) - in our gut microbiota by certain strains of probiotic bifidobacteria. CLA is a type of trans fat in the sense that it is both a trans- and cis- fat, and has been linked to potential health benefits which will be explored later. The most common occurrence of trans fats, however, occurs from the partial hydrogenation of unsaturated fats, namely vegetable oils. The partial hydrogenation process transforms the oils into a semi-solid product. Full hydrogenation would turn the unsaturated fats to saturated fats which cannot be trans- fats as they contain no double bonds.

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The process of hydrogenation, which is integral to the manufacturing process of trans fats, was first developed in the 1890’s by French chemist Paul Sabatier. In 1902, German chemist Wilhelm Normann patented the hydrogenation of liquid oils and went on to build a fat-hardening facility in Germany. During that time, another fat-hardening plant was built in Warrington, England which, in 1909, went on to begin manufacturing hardened fat. Also, in 1909, American company Procter & Gamble acquired the United State rights to the Normann patent and, in 1911, began selling Crisco - the first hydrogenated shortening. In the early 20th century, soy beans began to be imported into the United States. A byproduct of soybean processing, soybean oil, provided a potential answer to the shortage of butterfat plaguing the public at the time and, thanks to the newly discovered hydrogenation process and recent invention of refrigeration, a new type of margarine was developed. One of the unique features hydrogenated fats provide to margarine is the ability for it to be taken out of the fridge and remain spreadable - a quality butters, and other natural fats, lack.

Although there was some scientific suggestion as early as the mid 1950’s towards the negative health impact of trans-fats, animal fats earned the stigma of “most concerning fat source” until the early 1990’s. In 1994 the American Journal of Public Health recommended “Federal regulations should require manufacturers to include trans fatty acid content in food labels and should aim to greatly reduce or eliminate the use of partially hydrogenated vegetable fats.” (2)

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Health effects

As previously mentioned, the negative health effects of artificial trans fats have been known for a while. This study of 1997 increased plasma levels of “bad” low-density lipoproteins whilst simultaneously decreasing plasma levels of “good” high-density lipoproteins which correlates to an increased risk of coronary artery disease. Other possible health effects include (3):

- Interfere with essential fatty acid (EFA) metabolism. Trans fatty acids (TFA) compete with EFA’s for enzyme systems involved in the metabolism of EFA’s and, in animal models at least, have been shown to negatively influence EFA metabolism.

- Potential increase in risk of breast cancer. There is conflicting evidence for a correlation between trans fats and breast cancer, especially in post-menopausal European women.

- Potential increase in risk of colon cancer. In a study of 2001, scientists demonstrated correlations between trans fatty acid intake and an increased risk of developing colon cancer in those aged over 67. At a particular risk were postmenopausal females not taking hormone replacement and those not using NSAID’s (4).

- Diabetes and obesity. Studies carried out by the National Institute of Nutrition in Hyderabad, India showed that trans fatty acids increased insulin resistance by decreasing ones sensitivity to insulin. This action has implications in an increased risk of developing type-2 Diabetes and obesity.

Almost all recent studies looking in to the health effects of trans fat consumption conclude that it would be wise to reduce, if not eliminate, dietary consumption of trans fats.

Where are they found?

As previously mentioned, some trans fats are found in nature in the stomach of ruminants. These trans fats are produced by the biohydrogenation of plant oils in the gut of the animal by bacteria. The predominant trans isomers produced by ruminants are vaccenic acid and conjugated linoleic acid , whereas industrially produced trans fats are predominantly elaidic acid. While consumption of artificially produced trans fats have been shown to produce negative health effects, consumption of ruminant trans fats has been linked with several health benefits, most notably due to an improvement in blood lipid levels and inflammatory markers (CLA) (5). Cows which fed on pastures and had no supplemental feed - grass-fed cows - had 5x the amount of CLA in their milk compared to those fed typical dairy diets (6).

Ruminant trans fat sources:

- Dairy such as milk, cheese, yoghurts etc.

- Meat such as beef, lamb, goat and other ruminant animals.

Remember, grass-fed animals will have a higher amount of CLA than animals consuming a diet more commonly used in farming (notice how I didn’t say “normal diet”)

Industrially produced trans fat sources:

- Vegetable shortening

- Margarine

- Baked goods - Pastries, doughnuts, pies etc

- Microwave popcorn

- Fried fast foods

- Non-dairy coffee creamers

How to avoid them

Looking at the sources above, if you are following a healthy diet you should be avoiding trans fats by default. By simply aiming to eat foods which are as close to how nature intended them to be as possible, you pretty much eliminate the risk of consuming trans fats in your diet. If, for whatever reason, you still consume pre-made or pre-packaged foods, be sure to look for foods containing “partially hydrogenated -” and “trans-” in their ingredient list.

There is, however, a slight issue with this. In the UK, and other countries, there is no legislation restricting trans fat usage. This means there is no legal requirement to list trans fats in food packaging which renders the whole “look at the label” thing a bit pointless. Some honest food companies clearly state on their food packaging that they do not use trans fats (we salute you!) and with an increasing pressure from health bodies to ban the use of industrially produced trans fats (7), we might begin to see laws change around the world pretty soon.


Artificially produced trans fats have been linked to a plethora of side-effects which negatively impact our health and lack evidence of potential health benefits. The majority of health bodies urge the restriction, and ban, of trans fats. In 2018, the United States officially banned the use of trans fats, and the World Health Organisation has launched an initiative to ban the use of trans fats worldwide by 2023 (8). By following a natural, unprocessed, whole food diet you virtually eliminate the risk of consuming artificial trans fats.

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John Maitland

John Maitland is the co-founder of 'The Evolved Way.’ A personal trainer with over 10 years’ experience, he has worked alongside a wide range of leading CEOs, entrepreneurs and medical professionals. John is a keen athlete and holds a black belt in Shaolin Kung fu. A fan of the great outdoors, he can often be found exploring the British countryside and mountains...or breaking pine boards with his fingers.

Samson Hodin

Co-founder of 'The Evolved Way', and experienced personal trainer, Samson practices what he preaches. His own healthy lifestyle, which informs this site, is based on understanding the right way to eat and exercise, not excluding of course going out and enjoying life knowing you can still feel and look good.

#HealthyEating #AntiNutrients #Health



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