Trans Fats and Other Processed Foods

"Convenience is the enemy of nutrition"

Many forms of food processing reduce the quantity of omega 3 (n-3) PUFAs in our food, replacing them with much less beneficial compounds.

Why are foods processed?

Foods are processed to:

What happened to the natural ingredients that went into my food?

The food products that we buy in the shops often bear little resemblance to the natural ingredients that were used to make them.

Here are some types and elements of processed food that you may want to avoid:
When you consider buying a food product think about the transformations it has experienced on its way to your shopping basket. Understand precisely how it has been changed and what loss of nutritional value has occurred.

Food Philosophy: Transform your food and your health by using the best quality ingredients in their most natural state and by turning the everyday business of preparing and eating food into an important - but usually informal - ritual. Allocate more time to planning, presenting and enjoying your meals.

What happens to the PUFAs when oils are processed?

The processing of oils and fats results in degraded nutritional quality through:


Caused by drying, cooking and refining. Oxidation is promoted by heat, light and exposure to air. The hydrocarbon chain is broken, destroying the PUFA and resulting in the formation of less beneficial compounds.


Caused by de-hulling, bleaching, refining and deodorization. Triglycerides are broken down when they react with water. This creates free fatty acids, which are more prone to oxidation.


Caused by bleaching and hydrogenization. Trans fats are created while the PUFAs are lost.

Loss of tocopherols

Caused by refining and deodorization. Tocopherols, a form of vitamin E, are important anti-oxidants. They are required both pre and post-consumption of EPA and DHA to prevent oxidation and the resulting damage to cell membranes.

What are trans fats (trans-fatty acids)?

The creation of trans-fatty acids

In their normal (cis) form PUFA molecules are bent at the sites of their double bonds as the two hydrogen atoms, due to their proximity, repel each other. The angular shape of the molecule allows it to perform certain important physiological functions.

Trans-fatty acids form during hydrogenation, when a fatty acid molecule becomes twisted at the site of one or more of its double bonds so that the two hydrogen atoms end up on opposite sides of the carbon chain. This straightens the molecule because the two hydrogen atoms are no longer close enough to repel each other. The molecule now resembles a saturated fat in shape.

Naturally produced trans-fatty acids

Some trans-fatty acids form naturally in small quantities in the rumen (stomach) of ruminant animals such as cows and sheep during biohydrogenation.

Conjugated linoleic acid (CLA) is a trans-fatty acid produced by biohydrogenation and is therefore found in meat and dairy products. Unlike most trans-fatty acids, it is considered to have significant health benefits. These stem from its potential to combat atherosclerosis and cancer.

Artificially produced trans-fatty acids

By far the largest quantities of trans-fatty acids (up to 90%-95%) are created by industrial hydrogenation during the commercial processing of vegetable oils.

The harmful effects of trans-fatty acids

Trans-fatty acids disrupt the normal functioning of cell membranes. Because they use desaturase and elongase enzymes they also interfere with the conversion of EFAs into their derivative PUFAs via their metabolic pathways.

Trans-fatty acids increase harmful LDL cholesterol levels and reduce beneficial HDL cholesterol levels. They therefore increase the risk of cardiovascular disease (CVD) via atherosclerosis. They are also believed to increase the risk of cancer.

Common food sources of trans-fatty acids

The two largest food sources of trans-fatty acids are margarines and the shortenings that are used extensively in baked goods.

Find out about metabolic pathways

Hydrogenated oils

Why are oils hydrogenated?

Hydrogenation allows oils that are liquid in their original state to be used in solid food products like margarine. Commercial hydrogenation of vegetable oils creates products that:

How are oils hydrogenated?

Hydrogenated oils are manufactured by allowing natural oils to react with hydrogen under conditions of high temperature and pressure.

Oils that have been completely hydrogenated are fully saturated and do not contain any trans-fatty acids. They are chemically stable and have a long shelf life.

The harmful effects of partial hydrogenation

Partial hydrogenation produces trans-fatty acids and other harmful substances. The process is unpredictable in terms of the resulting chemical compounds and their physiological impact.

Hydrogenation transforms n-3 and n-6 PUFAs by changing their double bonds in the following ways:

Common food sources of hydrogenated oils

The main food sources of hydrogenated oils are margarines, shortenings and manufactured vegetable oils.