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Trans Fats: Health Risks, Sources and How to Avoid Them

Trans fat is a form of unsaturated fat that has been hydrogenated in order to make it more saturated. As a result, trans fat is more solid and stable at room temperature and less susceptible to spoilage than original unsaturated fat.

Fats and oils are made up of glycerol (three-carbon sugar alcohol that forms the backbone of fatty acids) and fatty acids (long molecular chains of carbon, hydrogen and oxygen). They are stored in the body as triglycerides (esters derived from glycerol and fatty acids), which also circulate in the blood. There are three major types of fat: saturated fats, unsaturated fats and trans fats. The type of a fat is determined by the number of hydrogen atoms attached to carbon atoms in the fatty acid molecular chain.

When there is the maximum possible number of hydrogen atoms attached to each carbon atom in the fatty acid molecular chain, we speak of saturated fat, because all bonds between carbon atoms are single (i.e., saturated). An unsaturated fat has one pair of hydrogen atoms in the chain missing. This leaves two carbon atoms connected by a double bond instead of a single bond. Fatty acids that have only one double bond in the chain are called monounsaturated, while those that have more than one pair of hydrogen atoms in the chain missing, and, therefore, more than one double bond, are called polyunsaturated.

Trans fats are unsaturated fats that have undergone hydrogenation. During this process, hydrogen is added to monounsaturated and polyunsaturated fats, typically a vegetable oil. In most unsaturated fats, hydrogen atoms are located at double bonds on the same side of a carbon chain (this type of configuration is known as “cis” or cis double bond). But, hydrogenation reconfigures some bonds so that hydrogen atoms end up on different sides of the chain. Then we speak of “trans” configuration. Most of the time, hydrogenation is partial, leaving the fat between 5-60% saturated. The end result is known as a trans fatty acid.

Health Effects of Trans Fats

Hydrogenation of unsaturated fats has several benefits. It turns liquid oils into solid fat, such as margarine, and extends their shelf-life by preventing rancidity. However, hydrogenating a fat makes it less healthy. Consuming trans fats causes an increase in both total cholesterol levels and the levels of low-density lipoprotein (LDL) – or so-called “bad” – cholesterol. In addition, trans fats also cause a drop in the levels of high-density lipoprotein (HDL) – or so-called “good” – cholesterol.

Cholesterol is a waxy, soft, fat-like substance in the blood. High levels of cholesterol in the blood can accelerate the build-up of cholesterol deposits on blood vessel walls, which can result in atherosclerosis. Hence, the increased levels of blood cholesterol are a major contributing factor to coronary artery disease. Research shows that ounce for ounce trans fats are far more likely to cause coronary heart disease than saturated fats. However, a typical westerner eats between four and five times more saturated fats than trans fats, which makes saturated fats a bigger health threat.

Sources of Trans Fats

Hydrogenated vegetable oil is the main source of trans fatty acids. Good examples of foods that frequently contain hydrogenated fats include margarines, baked goods, cakes, cookies, crackers, fast food and snack foods (e.g., French fries, deep-fried chips), peanut butter and vegetable shortening.

Pork, lamb, beef, milk, butter and cheese also naturally contain small amounts of trans fatty acids. However, animal foods also contain many vital nutrients. Therefore, it is primarily the trans fats from processed foods and hydrogenated oils that should be eliminated from the diet.

Many foods rich in trans fats also have high levels of saturated fats. This makes them doubly bad for a person’s health. In addition, some dietary supplements, such as energy and nutrition bars, also contain trans fatty acids.

Reducing Intake of Trans Fats

It is not recommended to completely eliminate trans fats from the diet. In any case, this would be largely impractical, because trans fats are present in too many foods, such as animal foods, that are important to overall nutrition. Eliminating trans fats entirely may result in inadequate intake of certain necessary nutrients and cause health risks. However, people should consume as little trans fat as possible.

People are urged to check the content of trans fats in the Nutrition Facts panel to help them avoid foods high in trans fat. In general, it is recommended to replace trans and saturated fats with unsaturated fats. For example, unsaturated fats can be found in canola, olive, soybean, sunflower and corn oils.

Where to Find More Information: Ban Trans Fats – an older website that is still worth reading