Q I thought I knew a lot about dietary fat, but I saw a phrase I didn't understand. What is an interesterified fat? — C.L.J., Winterville

A With all the latest news about the type of fat being more important than overall fat content of the diet and also on the negative health effects of trans fats, a new generation of fats in food products has been flooding the shelves. The process called interesterifcation, or the rearranging of fatty acids, makes oils, like palm oil, into a solid. The interesterified fats are replacing trans fats in some products. I asked Jessica Sharp, a third-year medical student to tell us about fat in our food. Here is what she learned.

You probably know that trans fats both raise your bad blood cholesterol and lower your good blood cholesterol. Not surprisingly, the new trans fat alternative appears to be following in the footsteps of its predecessor. New research suggests that interesterified fat may actually be worse for you than trans fats.

Since 1993, the FDA has required that saturated fat be listed separately on nutrition labels from unsaturated fat because of its damaging effects on the cardiovascular system. Saturated fat is known to raise the "bad" cholesterol in your blood (LDL) that leads to plaques in your arteries, which can eventually cause heart attacks and strokes. Food manufacturers looked for an alternative fat that would give a food product the similar texture and flavor as butter or lard. They found trans fats.

Unfortunately, researchers discovered that trans fats had the same "bad" cholesterol-raising effects as saturated fats. However, unlike saturated fat, trans fats were also shown to lower the "good" cholesterol (HDL) in your blood. HDL normally serves as a "clean up" molecule by picking up extra cholesterol from your cells and extra fat in your blood stream for transport back to your liver. So consumer advocates pushed the FDA to mandate companies list trans fat separately on the nutrition labels in the same way as saturated fat.

Once again, food companies worked to find "healthier" fat alternatives. Some companies actually try to produce healthier foods. Others appear to be more concerned that their cookies and cakes would not sell if they had nutrition labels with ugly heart-unhealthy fats listed on them. One of the alternative fats, interesterified fat, is proving itself to be yet another disappointment in the search for a healthy way to eat fatty foods.

In a recent study published in Nutrition and Metabolism, 30 volunteers took turns eating each of three controlled diets where the predominant fat source was either unsaturated fat, trans fat, or interesterified fat. Both bad and good cholesterol levels were measured along with blood sugar and insulin levels. Both interesterified fat and trans fat significantly raised LDL, lowered HDL, and elevated blood sugar. The interesterified fats, however, were found to raise blood sugar more than the other fats. This was a small study, but the participants had drastic changes in their blood cholesterol in only four weeks. More research is clearly warranted. In the meantime, if you want to avoid interesterified fats look for "fully hydrogenated oil" on the package's ingredients list. Fats that are less saturated are listed by names you are more familiar with like corn oil or sunflower oil or canola oil. These oils can be considered part of a healthy diet in moderation.

It is important to read labels carefully and to remember that moderation is the key. A box of cookies that is labeled as "healthy" or "low fat," can still be high in calories, sugar or hidden fat. For now, it appears a heart-healthy diet is made of up more whole foods like fruits and vegetables and less sweets and other processed foods.

Professor Kathy Kolasa, a registered dietitian and Ph.D., works with the Family Medicine Center, Brody School of Medicine at ECU. Contact her at kolasaka@ecu.edu, or C/O The Daily Reflector, P.O. Box 1967, Greenville, NC 27835.