"Interesterified" fats poised to replace trans fats

January 19, 2007 Shelley Wood

Kuala Lumpur, Malaysia - A new modified fat made through a process called interesterification is shaping up to be the chief contender to substitute for the trans fats being banished from processed foods and restaurants. But researchers who compared the effects of different fats in human diets are warning that interesterified fats may be just as bad as the trans fats they are poised to replace [1].

Writing in a paper published online January 15, 2007 in Nutrition & Metabolism, Dr Kalyana Sundram (Malaysian Palm Oil Board, Kuala Lumpur) and colleagues report that compared with a diet high in palm olein (a saturated fat), diets high in either trans fats or interesterified fats significantly raise both LDL/HDL ratio and fasting blood glucose while significantly reducing fasting insulin levels.

The study was supported by the Malaysian Palm Oil Board, which has a major stake in the ongoing fat wars and the hunt for a healthful, stable fat with a long shelf life.



Meddling with Mother Nature's molecules
In an interview with heartwire, senior author on the study, Dr KC Hayes (Brandeis University, Waltham, MA), explained that interesterification grew out of the observation that stearic acid, the fatty acid predominant in chocolate and cocoa butter, unlike other saturated fatty acids, did not appear to raise cholesterol levels. "People got the idea, hmm, let's just take the saturated fatty acid stearic acid out of different oils . . . and put it into an oil like soybean oil. Why not? There's three fatty acids hanging off of soybean oil, why not replace one of the polyunsaturated fatty acids, which makes it an oil, with a neutral saturated fatty acid, and you harden or solidify the product. . . . This is the coming rage in replacing trans fats."


But Hayes, who says he's "been looking at fats and oils for 35 years," is concerned about the physiological effects of meddling with fat molecules. His own research has suggested that replacing a polyunsaturated fatty-acid molecule in vegetable oil with stearic acid might pose problems if that stearic acid is placed in the middle fatty-acid position on a fat molecule, since it is not as easily metabolized.

"That's not the way nature set it up. If you look at cocoa butter, which is this nice neutral fat, all of the stearic-acid molecules are on the outside, they are in the one and three positions, they're almost never in the middle. So now when I artificially put my stearic acid in I get about equal amounts [of saturated fatty acid] in positions one, two, and three."




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