What Are Trans Fats? - Definition, Sources & Examples

Instructor: Wendy McDougal

Wendy has taught high school Biology and has a master's degree in education.

The majority of trans fats are artificial fats created by adding hydrogen to liquid vegetable oil to make it into a solid. Once found in many different foods, the use of trans fats has been drastically reduced. Learn more about these fats and take a quiz at the end.

What are Trans Fats?

Have you ever used shortening for cooking or baking? Perhaps your mom or grandma relied heavily on the large can of thick, greasy fat. Today the popularity of shortening has dwindled. In fact, the very mention of this type of fat often creates uproar in health-conscious communities. This is because shortening is an example of a trans fat. Once considered a great alternative to oils and butter, trans fats are now deemed one of the most unhealthy substances on earth. But what exactly are these fats and why are they being run out of town?

Shortening, the Quintessential Trans Fat
can of crisco

Trans fats are a type of fatty acid. This is just a fancy way of saying that they are part of a fat molecule. Trans fats are found naturally in very small amounts in some meat and dairy products. However, the majority of trans fats are artificially created by a chemical process known as hydrogenation. In short, hydrogenation turns a liquid oil into a solid fat. In this lesson, learn more about trans fats and gain a better understanding of why they exist and how they affect our health.

How and Why are Trans Fats Made?

This is a day and age in which people have been trained to read nutrition labels on food containers. You have probably seen the ingredient, partially hydrogenated vegetable oil on a cracker box. If you are health-conscious, you might recoil with horror and immediately return the product to the shelf. If this ingredient is listed, then that means it contains trans fats. So what does that term actually mean? Let's take a closer look at a fat molecule to better understand.

A fat molecule is made up of one glycerol molecule bonded to three fatty acids. The fatty acids are made of a carbon backbone bonded to hydrogen atoms. Some fatty acid chains have the maximum number of hydrogen atoms attached onto their carbon skeletons. This means that they're saturated, meaning it's full. Do you recognize the term saturated fat? You probably saw it in the nutrition facts of many snacks. Most animal fats are examples of saturated fat, and they're solid at room temperature. These are typically the unhealthy fats.

Structure of a Fat Molecule
fat molecule

If a fatty acid chain does not have the maximum number of hydrogen atoms attached, then it's unsaturated, meaning it's not full. You undoubtedly recognize this term as well. Unsaturated fats are usually plant-based, and are typically liquid oils at room temperature. Examples of foods containing unsaturated fats are olive oil and avocados.

Saturated vs. Unsaturated Fatty Acids
fatty acids

Now how does this relate to trans fats? It's because of those available spaces in the fatty acid chain that scientists made their brilliant discovery in the early 1900s. Scientists realized that they could add hydrogen atoms to fill up most of the spaces on an unsaturated fatty acid. By this process of hydrogenation, they were able to create a solid, more saturated fat that looked like butter and lard but was much cheaper.

This man-made fat, or trans fat, also had a much longer shelf life. Companies that produced the masses of cookies, crackers, doughnuts and fried foods jumped at the chance to use this product in order to save money and increase shelf life of these foods.

The Problem With Trans Fat

As consumption of these foods grew in popularity, unfortunately so did the waistlines of those consumers. The obesity rate grew, as did incidents of heart disease and high cholesterol. By the 1990s, it was clear that products with trans fats were contributing greatly to these problems. And by then studies had shown that trans fats were a double whammy. They not only increased the bad cholesterol, but also decreased the good cholesterol.

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