Do cooking oils produce trans-fat on repeated usage?

By Harold Gunatillake

 

Dr Chris Pulle of BWFF forum states, “My guess is that Virgin or not, coconut oil must not be re-used, since it might contain “transfats” that are the real killer and give coconut oil (being the most saturated of oils) a bad name”.

Dr Pulle’s comment inspired me to write this article.

We know that trans fats are harmful to the body. On June 16, 2015, the Food and Drug Administration (FDA) came to a decision to ban artificial trans fats in the U.S. food supply. They do occur naturally in some foods, such as meat and dairy products. There
is a difference between naturally occurring trans-fat and artificially produced trans fats, like in Margarine, used for frying, baked goods, confections and as spreads on bread.

Artificially created trans fats are produced through a process of hydrogenation of mostly plant-based vegetable oils and animal fat turned into soft solids such as shortening or margarine. These artificially made trans fats are also referred to as partially
hydrogenated oils.

Naturally occurring trans-fat in meat and other foods pose no health risk, as the amount is so small.

On the contrary the artificial trans fats are very unhealthy and has no health benefits, and further FDA has banned the production for the same reasons.

The question arises whether natural cooking oils do produce trans-fat on repeated usage, though most of the harmful trans fats come from the hydrogenated oils, which involves high temperature, and high pressure and goes through a series of stages, including adding deodorants and carcinogenic chemicals.

It is known that repeated usage of cooking oils does turn into trans-fat and also this depends on what cooking methods are used.

Normal cooking oils can undergo a process of lipid oxidation at high temperatures speeding up the formation of trans fats.

This is more likely in the unsaturated fats where less hydrogen atom linkage exists in them. In saturated fats hydrogen atoms cannot creep in by any process of hydrogenation because all carbon atoms are linked to hydrogen atoms with no
vacancies.

This is where coconut oil scores that it is one oil that can be used repeatedly many a times. Our Ammes (domestics) knew it and they did use the same coconut oil repeatedly in their cooking processes. So, coconut oil has no trans-fat and can never be hydrogenated into a trans-fat.

Why did FDA ban Trans Fat? There is a consensus now that trans fats may contribute to heart disease.

Our bodies cannot differentiate between good fat and trans-fat. When you consume trans-fat through cooking methods or spreads on bread, those fats take the place of normal fat in the cellular walls and the cells of the body that carries on the metabolic processes. Trans fat seems to interfere with normal cellular metabolic activities and plays havoc.

So, remember it is only vegetable oils that can turn into a semi-solid or solid state through the process of hydrogenation.
Food companies and restaurants use trans-fat to improve the taste and texture of food and also increase shelf life of food products.

Trans fats cause high bad cholesterol (LDL) levels in your blood, clogs the vessels and increases the risk of heart disease and stroke.

So, beware those margarine lovers.

Now coming back to cooking oils turning into trans-fat, as we mentioned earlier, depends on the way the oil is used for cooking.
Stir frying used mostly in Chinese cooking increases the amount of trans fatty acids and that oil should be discarded after one usage. High heat and stirring results in trans-fat conversion.

Deep frying used many times in high temperatures also produce some trans-fats. Other forms of cooking methods may not raise trans-fat content in the oil.

The trans fat generated through both stir frying and deep frying in reheated oils may be still within the recommended safe limits, but frequent usage of such re-heated oils may add and exceed the maximum recommended limit.

In Sri Lanka, there are no limits or restrictions introduced by the government not to use re-used oils, and it is quite common to use due to economic saving without realizing the damage they cause.

Fortunately, most homes use coconut oil, and it can be used repeatedly being a saturated fat and cannot be further hydrogenated.
But unfortunately, cheaper canola and other vegetable oils are sold by different brand names, and most people now use these brands, unfortunately.

WE strongly recommend the usage of genuine virgin coconut oil for Asian cuisines.

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