What are interesterified fats and why are they used?

Interesterified fats are used as replacements for partially hydrogenated oils to help reduce or eliminate trans fats while maintaining the taste, texture, and flavor of manufactured foods. Interesterified fats are typically created by blending solid fats (e.g., fully hydrogenated soybean oil, palm oil) with liquid oils (e.g., soybean oil, canola oil) then using a process to interchange the fats in order to achieve specific functional attributes in foods such as texture, mouth feel, and structure. Interesterified fats are solid or semi-solid at room temperature.

How long have interesterified fats been in use?

Interesterified fats were first introduced as food ingredients in the US in the1950s, in Europe in the 1920s and have been used extensively in Europe for 15 years to replace partially hydrogenated oils.

What products contain interesterified fats? 

Interesterified fats work best in products where a solid or semi-solid “fat” is used such as margarines, spreads and shortenings, and in confections and baked goods where they contribute to texture, mouth feel, structure, and aeration.

Didn’t a recent study show that interesterified fats have a negative health impact?

The study showed that subjects following a diet containing either a trans fat-containing, partially hydrogenated soybean oil or an interesterified soybean oil had lower HDL (“good”) cholesterol levels compared to subjects following a diet containing palm oil, which contains mostly saturated fats. In addition, the subjects following the diet with the interesterified fat had higher blood sugar levels and metabolized blood sugar more slowly. However, it’s important to note that the interesterified fat used in the study contained an unusually high amount of saturated fat (59%)—much higher than is typically used in food products. In addition, Walter Willet of the Harvard School of Public Health stated in a Science News article about the study that "The fatty acid composition of the three diets was very different, so it’s difficult to distinguish the effects of interesterification from the effects of the fatty acids." For the results to be meaningful, the study should be replicated with typical formulations of interesterified fats in realistic amounts. (Study cited: Nutrition & Metabolism January 2007 http://www.nutritionandmetabolism.com/content/4/1/3)

Is there other research on the health effects of interesterified fats and, if so, what does it show?

Yes. The literature contains many studies examining the impact of interesterified fats on health effects in humans. When compared to fats containing trans fats, interesterified fats tend to decrease LDL (“bad”) cholesterol. Specifically, numerous studies in humans have demonstrated than interesterified fats appear not to change LDL cholesterol, glucose, or insulin levels compared to non-interesterified fats. (Study Cited: Lipids July 2001 http://www.springerlink.com/content/r77882888u287123/?p=a0d737e8d75b43718633ad076fa70f59&pi=0)

How can consumers tell whether a product contains interesterified fats?

You know for sure that a product contains interesterified fats when the term "interesterified" appears on the product's ingredient list. However, the use of this term is optional. When “fully hydrogenated vegetable oil,” “palm oil,” and/or “palm kernel oil” are listed, the product may or may not contain interesterified fat.