New kind of fat,
new kind of problem

A ban on trans fats in New York City restaurants in December has ignited a search for a different kind of modified fat. However, according to research from Brandeis University in Waltham, Mass., the alternative may not be an improvement.

Trans-fatty acids, found commonly in baked goods, processed foods, and restaurant cooking, have come under attack because they raise LDL cholesterol and lower HDL ("good") cholesterol, contributing to heart disease. The most popular alternative is interesterified fats, a process that unnaturally rearranges the fat molecules after hydrogenation to generate stearic acid--a saturated fat that doesn't spike levels of LDL ("bad") cholesterol.

Yet according to research published online in Nutrition and Metabolism, interesterified fats do raise blood glucose and depress insulin (both common precursors to diabetes) when compared to natural saturated fats like palm oil. What's more, the new fat still lowered the amount of beneficial HDL cholesterol.

"One of the most interesting aspects of these findings is the implication that our time-honored focus on fat saturation may tell only part of the story," explained biologist and nutritionist K.C. Hayes online in the publication. "Now it appears that the actual structure of the individual fat molecule is critical." Hayes collaborated with Dr. Kalyana Sundram, nutrition director for palm oil research at the Malaysian Palm Oil Board in Kuala Lampur. Both helped develop Smart Balance butter spreads, a vegetable oil butter alternative that improves the ratio of good to bad cholesterol.

In the study 30 people ate all three diets (trans fats, interesterified fats and natural unmodified fats) in rotation for four weeks each. While trans fats also adversely affected glucose levels, interesterified fats were worse, raising blood sugar 20% in just one month.

"Whether this reflects the amount of test fat consumed, underlying genetics of the specific population examined, or some unknown factor, requires further study because the apparent adverse impact on insulin metabolism is a troubling finding," Sundram said.