Trans Fat Facts

Trans fatty acids, or trans fats, are unsaturated fatty acids that have at least one double bond in the trans configuration. Most dietary trans fats are a byproduct of the hydrogenation of vegetable oils, when the oil is heated in the presence of a metal catalyst and hydrogen. These fatty acids are more saturated than natural vegetable oils and able to pack together more tightly. As a result, trans fatty acids are more solid at room temperature and behave more like saturated fatty acids. 


Health Implications

Overwhelming scientific evidence indicates that trans fatty acids—like saturated fats and dietary cholesterol—raise LDL (or "bad") cholesterol. Because of the heart health risks, the U.S. Food and Drug Administration issued a trans fatty acid labeling rule, Trans Fatty Acids in Nutrition Labeling, Nutrient Content Claims and Health Claims" on July 11, 2003 (68 FR 41434 at 41468-41470). The rule stated that, beginning January 1, 2006, labels on food sold in the U.S. must list the amount of trans fatty acids in the product if it is more than one half a gram per serving.


The primary source of trans fats is partially hydrogenated soybean oil, which has long been popular among U.S. food manufacturers for its low cost and its flexibility in meeting the demands of a wide variety of applications. Partially hydrogenated soybean oil was developed to replace saturated fats, such as butter and lard, in food formulations.Food manufacturers continue to search for satisfactory alternatives to hydrogenated oils in order to reduce trans fat levels as far as practicable (a small amount of trans fat occurs naturally in a number of foods including some meats).

Trans Fat Alternatives

When removing partially hydrogenated soybean oil (a common ingredient in everything from snack crackers to salad dressings), food manufacturers have had two basic options.  The first is to replace the soybean oil with another type of oil.  The palm oil industry has been very active in trying to convince food makers to use the oil of the palm fruit for this purpose, since it does not need to be hydrogenated to fulfill the requirements for many applications. The U.S. has dramatically increased imports of palm oil since 2005, mostly in response to the trans fat labeling regulations.  Some canola and sunflower oils have also been substituted for hydrogenated vegetable oils in food products; notably, Frito Lay made a high profile switch by announcing in May of 2006 that its Lay’s and Ruffles snack chip lines would be made with NuSun brand sunflower oil.The second approach, favored by the American soybean industry, has been to reformulate the soybean oil itself (or to create soybeans that contain a more stable oil) to avoid giving up market share for soybean producers. ADM’s NovaLipid oils are one example of this. Rather than being hydrogenated, NovaLipid oils are given the same functional properties in a process called interesterification, using an enzyme created for this process by Novozymes A/S.The United Soybean Board has funded research into creating soybeans that require little or no hydrogenation. The primary focus of this research and development has been creating a soybean the oil of which is low in linolenic acid. This reduces or eliminates the need for hydrogenation and thus does not contain trans fats. Monsanto Company and Pioneer Hi-Bred have both developed such soybeans (with between 2.5 and 3 percent linolenic acid) and made strategic agreements with major soy crushers to process the beans.  A small Iowa firm called Asoyia markets an ultra-low linolenic (about one percent) soybean variety.Many other efforts to develop marketable solutions to the trans fat dilemma are underway but as yet commercially unrealized.

Additional Resources

American Oil Chemists’ Society:
American Palm Oil Council:
European Society for the Science and Technology of Lipids:
The Institute of Shortening and Edible Oils:
National Sunflower Association:
United Soybean Board:

Content for the Trans Fat page provided by Soyatech