crispy potato chips

Trans fats are hydrogenated fats often used in potato chips and other snack foods.

Trans Fat

Also Known As Trans Fatty Acids

What are Trans Fats?

Trans fat is a kind of unsaturated fat. What differentiates trans fat from other unsaturated fats is that some double bonds in trans fat are in trans configuration, rather than the cis configuration of the other fats.


There are two sources of trans fat.1 It can be produced naturally in the guts of some grazing animals such as cattle and sheep. Meat and milk have this kind. It can also be created during the partial hydrogenation process to produce partially hydrogenated oils (PHOs) from vegetable oils, which formerly were often used in foods like frozen pizza, grain-based desserts, ready-to-use frostings, refrigerated dough products, vegetable shortening and stick margarine.

The chemical structure of trans fat.

The chemical structure of trans fat.


Trans fat can increase the risk of developing cardiovascular disease.1 It increases the level of low-density lipoprotein cholesterol and decreases the level of high-density lipoprotein cholesterol in the blood. The Dietary Guidelines for Americans recommends keeping the intake of trans fat as low as possible.


Trans fat is a component of PHOs. The partial hydrogenation process introduces hydrogen to the double bonds of vegetable oils and converts some unsaturated fatty acids to saturated fatty acids. This process solidifies the oil, increases its resistance to rancidity, and changes its function. PHOs impart a very smooth, creamy, desirable texture to food products that require tenderization and moisture.2 It is also a process for producing shortenings and margarines.2

The double bonds in vegetable oils are in the cis configuration. During the partial hydrogenation process, the cis configuration may convert to a trans configuration, which creates trans fat. This conversion cannot be controlled or avoided when partial hydrogenation is applied.


To eliminate trans fat, PHOs produced from the former partial hydrogenation method have to be replaced. Palm kernel oil is the most prevalent substitute for PHOs.2 New methods have been used to produce shortenings and margarines, like blending fully hydrogenated oils with other oils, or interesterification.2

FDA regulation

The primary dietary source of artificial trans fat in processed foods, PHOs, are not GRAS for use in food, as regulated by the FDA on June 16, 2015.3 By June 18, 2018, manufacturers must ensure their products no longer contain PHOs for uses that have not been authorized by the FDA.4 Because trans fat cannot be totally eliminated from foods, the amount of it has to be labelled.5 If the food contains less than 0.5 g of trans fat per serving, 0 g of trans fat can be declared in the Nutrition Facts Label.1


  1. U.S. Food & Drug Administration. “Trans Fat.”, Accessed 24 Sept. 2017.
  2. Bakerpedia. “Partially Hydrogenated Oil | Baking Ingredients.” Accessed 24 Sept. 2017.
  3. U.S. Food & Drug Administration. “Constituent Updates – FDA Takes Step to Remove Artificial Trans Fats from Processed Foods.” U S Food and Drug Administration Home Page, Center for Food Safety and Applied Nutrition, 16 June 2015,
  4. U.S. Food & Drug Administration. “Food Additives & Ingredients – Final Determination Regarding Partially Hydrogenated Oils (Removing Trans Fat).” U S Food and Drug Administration Home Page, Center for Food Safety and Applied Nutrition, 20 June 2017, Accessed 24 Sept. 2017.
  5. U.S. Food & Drug Administration. “Labeling & Nutrition – Changes to the Nutrition Facts Label.” U S Food and Drug Administration Home Page, Center for Food Safety and Applied Nutrition, 19 June 2017, Accessed 24 Sept. 2017.