Trans-fatty acids, which became ubiquitous in baked goods, processed foods and restaurant cooking decades ago because of their shelf life and other properties, are now being abandoned by many producers of commercial products such as cookies, crackers, pies, doughnuts, and French fries because they raise LDL ("bad") cholesterol, lower HDL ("good") cholesterol and contribute to heart disease.
The Malaysian-Brandeis collaboration compared trans-rich and interesterified fats with an unmodified saturated fat, palm olein, for their relative impact on blood lipids and plasma glucose. Thirty human volunteers participated in the study, which strictly controlled total fat and fatty acid composition in the subjects' diet. Each subject consumed all three diets in random rotation during four-week diet periods. This study further confirmed previous studies in animals and humans, indicating once again that trans fats negatively affect LDL and HDL cholesterol. Surprisingly, the interesterified fat had a similar, though weaker impact on cholesterol.
"In this study we discovered that trans fat also has a weak negative influence on blood glucose. The newer replacement for trans, so-called interesterified fat, appears even worse in that regard, raising glucose 20 percent in a month," said Hayes.
"This is the first human study to examine simultaneously the metabolic effects of the two most common replacement fats for a natural saturated fat widely incorporated in foods. As such, it is somewhat alarming that both modified fats failed to pass the sniff test for metabolic performance relative to palm olein itself," noted Sundram.