Lenore Greenstein: Determining trans-fat levels may take some detective work

Trans-fats are made from liquid fats or oils by adding hydrogen (thus the term hydrogenated), and were developed in the late 19th century in Germany as a way of manipulating liquid vegetable oil.

The result was partially hydrogenated fats or trans-fats, which became solid at room temperature. They rapidly entered our food supply, largely in the form of solid shortening such as margarine and Crisco, because this process of hydrogenation increases the shelf life and keeps in the flavor of many food products.

Avoiding trans-fats in the diet is an important part of prevention of heart disease, since trans-fats raise blood cholesterol levels, in particular the LDL, or bad cholesterol, increasing the risk of clogged arteries leading to coronary problems. Trans-fats also reduce the HDL, or good cholesterol, and have been shown to increase triglycerides, another lipid or fat in the bloodstream.

Trans-fats are not in favor in terms of other diseases, since they are also involved with increasing the chance of diabetes.

According to Walter Willett, chairman of the department of nutrition at the Harvard School of Public Health, some short-term studies show that trans-fat increases insulin resistance, which is the underlying mechanism that causes Type 2 diabetes.

A recent study published in the Archives of Neurology showed more than 800 people over age 65 who had the highest intake of saturated or trans-fats were at more than twice the risk of Alzheimer's disease as compared with persons with the lowest intake of such fats. A high intake of unsaturated, unhydrogenated fats seemed to offer a slight protection against Alzheimer's, however.

By Jan. 1, 2006, the nutritional facts labels on foods and dietary supplements must contain a line that lists the amount of trans-fat in the product. Currently only some manufacturers' labels contain this information. So until manufacturers are required to put the trans-fat content on nutrition labels, you're going to have to do a little detective work yourself.

Trans-fats are often called "phantom" or "stealth" fats, since they hide in many foods, such as most (but not all) margarines, crackers, cookies, mass-produced pastry products, snack foods, frozen dinners, breads, some cereals, the oil used for deep-frying in fast-food restaurants and in other foods that contain saturated fat.

Here are some other places they often lurk: French fries and fried chicken at fast-food places, commercial baked goods like muffins, cakes and their icing, doughnuts, crackers (even "healthful" whole-wheat ones) pie crusts, biscuit mixes, frozen waffles and popcorn.

How can you learn if the foods you are eating contain trans-fats? One way is to look at the list of ingredients in a food product to see if there is vegetable shortening or vegetable oil described as "partially hydrogenated." That means that there are solid trans-fats in the product. Another method is to look at the total amount of fat on the label, and then add up the amount of saturated, and polyunsaturated or monounsaturated fats that are listed below. The amount that is missing from the total represents the amount of trans-fats.

Example: A product that has a total of 6 grams of fat, consisting of 2 grams of saturated and 2 grams of polyunsaturated, will leave a remainder of 2 grams of trans-fats that are not listed. This means that the total amount of unhealthy fats from both saturated and trans-fats equals two-thirds of the entire product, or 4 grams out of a total of 6 grams of fat. Hardly a recommendation for those who are following heart-healthy diet.

Lenore S. Greenstein is a registered and licensed dietitian in private practice in the Naples area.