OVER the last few years the term trans fat has become a dirty word in the fast-food industry and many packaged foods now proudly proclaim themselves to be trans fat free. Well, great, you might think. However, you’d be wrong …
The processing technique that creates trans fat is called partial hydrogenation. If you partially hydrogenate soy oil, you’ll get trans fats. If you partially hydrogenate canola oil, you’ll get trans fats. So, the blend doesn’t really tell us much. The big question is how is the blend processed?
This is where a potential problem lies – a technique called interesterification. Over the past few years, foods prepared with partially hydrogenated oils have come to be known far and wide as a health threat, linked to higher risk of heart disease and cancer. Most of us really want trans fat free foods. But food manufacturers and restaurant managers have balked at turning away from the convenience of partially hydrogenated oils. That’s why many of them have started to use oils processed by a new method: interesterification – yum, that sounds healthier already! Then they market them as trans fat free.
Like partially hydrogenated oils, interesterified oils have a long shelf life, which makes them just about as appealing to restaurants and food manufacturers as oils with trans fats. But there is one little catch: interesterified fats may be classed a trans fat free, but they are nearly as bad for you as trans fats.
From bad to trans fat free worse
Nutrition and Metabolism published a study that compared the effects of three oils: interesterified soybean oil, partially hydrogenated soybean oil and palm oil. Three different diets were prepared in which 30 percent of calories came from one of the three oils. Thirty subjects followed each of the diets over the course of three study phases. Each phase lasted four weeks. Two key results stood out:
HDL cholesterol levels dropped on the interesterified fat diet. Insulin levels dropped 10 percent on the partially hydrogenated soybean oil diet, but dropped more than TWICE as much on the interesterified fat diet, causing average blood sugar to rise by an alarming 20 percent
More research will be needed to confirm these results. Hopefully that research is underway, because one of the study authors, Dr. K.C. Hayes of Brandeis University, said: “interesterification is probably the number-one process that will replace trans fats.”
In the meantime, Dr. Hayes offered a very useful tip on how to determine if a food product contains interesterificated oil. Just check the nutrition panel and look for the words ‘fully hydrogenated’. Fully? Partially? Personally, I think it’s time call the whole hydrogenated thing off.