Interesterifed Oils – What Are They Doing in My Food?

Evil Oils?

“Trans fat free” – that’s a good thing, right?  It sure is. But are trans-fat replacements any better?  Not always.

Interesterified oil is one such example. To understand what it is, let’s recall why trans-fatty oils were such a hit to begin with. Some food applications require  the presence of fats that are solid in room temperature. For this reason, lard and butter were used for centuries in baked goods and to spread on bread. Then we learned, in the Sixties and Seventies, that butter and lard were unhealthy. Liquid oils were not good enough at room temperature, because, well, they were liquid.

And so a  process called hydrogenation was invented, and it enabled food manufacturers to firm up the liquid oils by bombarding them with hydrogen molecules and altering the state of the fatty acids comprising the fat molecules.

All oils and fats are composed of fatty acids. Fatty acids are molecules with a mix of carbon, oxygen, and hydrogen atoms. Some fatty acids are “saturated” and others are “unsaturated.” The main difference between the two types of fats is the amount of hydrogen atoms they contain. Saturated fatty acids have much more hydrogen atoms in them. It hardens them into a more solid substance.

The more you hydrogenate an oil, the harder it gets. Fully hydrogenated oils are too hard, but if you only partially hydrogenate an oil, you get the desired consistency.

Trans-fats are the result of partially hydrogenating oils to reach a semi solid state at room temperature. Unfortunately, science has determined that trans-fats cause serious heart health issues.

Manufacturers needed a replacement. What did they do? They mixed fully hydrogenated oils with non-hydrogenated oils. Thre result is called … Interesterified oil.

Is interesterified oil healthy or dangerous? Not enough research has been conducted on these fats to really know. Some studies show it’s fine, others not. In any case, no long term research has been conducted. Which leads us to our fundamental recommendation – don’t turn yourself or your kids into lab rats for the food industry: Try to avoid foods with interesterified  oils and fats.



Hayes KC, Pronczuk A. Replacing trans fat: the argument for palm oil with a cautionary note on interesterification. J Am Coll Nutr. 2010;29:253S-284S.

Sundram K, Karupaiah T, Hayes KC.  Stearic acid-rich interesterified fat and trans-rich fat raise the LDL/HDL ratio and plasma glucose relative to palm olein in humans. Nutr Metab. 2007;4:3.

Berry SE.  Triacylglycerol structure and interesterification of palmitic and stearic acid-rich fats: an overview and implications for cardiovascular disease. Nutr Res Rev. 2009;22(1):3-17.

  • Violet

    Great info! Thanks!

  • Carol

    Correction: “The main difference between the two types of saturated fat…” I think you mean “the two types of fat.”
    Note: hydrogenation goes back 100+ years. Crisco was introduced in 1911; it was the first vegetable shortening (from hydrogenated oil). It wasn’t developed for health reasons, but for longer shelf life and lower cost.

    • Fooducate

      Yes, thanks for the correction.

  • Michelle Schulp

    Except now they’ve found butter, lard, coconut oil, etc. are much better for you than nearly all of the vegetable oils we’ve tried to use in their place…

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