Trans Fat Substitute May Be Just as Bad

Results from the rush to remove Trans Fats from our foods, may cause new problems.

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].

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.

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."

After four weeks, both the trans-fat and interesterified-fat diets significantly elevated both the LDL/HDL ratio and fasting blood glucose, with the interesterified-fat diet boosting LDL/HDL ratios by almost 20% as compared with the saturated-fat (palm-olein) diet. Fasting insulin at four weeks was 10% lower following the trans-fat diet and 22% lower following the interesterified diet, as compared with the saturated-fat diet. Postprandial glucose on the interesterified diet was also striking higher than on the saturated-fat diet.

According to Hayes, interesterified fats are already on the market, being used primarily as a replacement for trans fats in margarines and baked goods. Unlike trans fats, which are required to be listed on labels, interesterified fats are typically listed as "fully hydrogenated" or even as "interesterified fats." Because there has been little public attention being paid to these new manufactured fats, Hayes worries that people may not be aware of the potential harm.

Indeed, whether or not there is harm to be had in interesterified fats remains to be seen.

He continues, "From my perspective, natural fats are still nature's way of doing it. If nature's fat does something you don't like, try blending it with a natural fat that you do like, and that’s the way to get to the best solution, as opposed to modifying it, as opposed to saying, we'll trick nature and make this partially hydrogenated or fully hydrogenated."

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.

Source: Diabetes In Control: Sundram K, Karupaiah T, Hayes K. 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 Jan. 15, 2007; doi:10.1186/1743-7075-4-3. Available at: http://www.nutritionandmetabolism.com.