The skinny on fats.

The ubiquitous Nutrition Label printed on virtually everything edible, is missing vital information on the types of fats present. It is important to know more than simply the amount of total fat or even the amount of cholesterol and saturated fat in a product. One fat that is particularly powerful in its artery-clogging, coronary-heart disease promoting impact--trans fat or trans fatty acids--isn't even mentioned at all on Nutrition Labels. The Food and Drug Administration may soon require food manufacturers to include information about trans fat content on Nutrition Labels.

Fats are necessary for the essential fatty acids your cells need to carry on the business of life, which is why a healthy diet requires that 20% to 30% of your daily calorie intake comes from fat. But as you know, all fats are not created equal. There are good fats, bad fats, and even worse fats. Fats are generally classified as saturated (those fats come from animal sources like meat and dairy products), monounsaturated (found in olive oil and canola oil), and polyunsaturated (found in flaxseed and certain fish oils). Relatively new to the consumer is another category, the trans fats, which arise when mono-or polyunsaturated fats have hydrogen atoms added to retard spoilage, a process known as hydrogenation. Trans fats do occur naturally in animal products but this source is very small compared to the trans fats found in processed foods.

What makes these fats good or bad? Saturated fats raise artery-clogging total cholesterol and low-density lipoproteins (LDLs). Monounsaturated fats, in general, lower LDL levels without affecting the good, high-density lipoprotein (HDL) levels. Polyunsaturated fats reduce the levels of both LDL and HDL but they have a good side as well: they are the source of omega-3-fatty acids, which have been shown to provide protection against blood clots. Trans fats raise levels of LDL, maybe even more dramatically than saturated fats do, which is why trans fats may be worse than just bad.

Coronary heart disease is still the number one cause of death in the United States. Reducing the consumption of trans fats found in margarine, crackers, fried foods, cookies, doughnuts and many other foods could reduce the incidence of heart disease, and can certainly help health-conscious consumers manage dietary fats. In addition, once forced to come clean with trans fat levels, manufacturers may be inspired to reduce trans fat levels in their products.

For now, your best guess is to suspect high levels of trans fat if "partially hydrogenated oils" are listed as a major ingredient. Best of all, of course, is to reduce saturated fat consumption by cutting back on meats and choosing low-fat dairy. Reduce trans fats by avoiding packaged snack foods, fried foods, "fast" food, and hard margarine; and increase your intake of beneficial fats like olive, canola, flaxseed, and fish oils. (New England Journal of Medicine, 1999, Vol. 340, No. 25, pp. 1933-1940; FDA announcement, November, 1999)