In the third part of The Early Show's Healthy Heart series, we examine trans fatty acids and why this commonly used product is under such intense scrutiny.
Trans fats are commonly found in vegetable shortenings, some margarines, crackers, candies, cookies, snack foods, fried foods, baked goods and other processed foods made with partially hydrogenated vegetable oil. A small amount of trans fat is found naturally, primarily in dairy products, some meat and other animal-based foods.
The Early Show medical correspondent Dr. Emily Senay shares the facts about the product.
Trans fat is made when manufacturers add hydrogen to vegetable oil -- a process called hydrogenation. Hydrogenation increases the shelf life and flavor stability of foods containing these fats.
In the early 1900s, a German scientist found a way to convert oils into solids, which was called "margarine." Soon after, margarine was found in the United States. Senay explains there was a lot of resistance to it at first from the dairy and meat industry. But it soon caught on because it didn't soften the same way butter did and it was cheap.
Margarine really became popular when saturated fats -- contained in butter and lard products -- were said to cause heart disease. On the other hand, margarine, which was filled with trans fats, was promoted as "cholesterol-free" and good for you.
Over the years, several scientists cautioned consumers about the risks of trans fats. But it wasn't until recently that people began to heed those warnings, says Senay.
Scientific evidence shows that consumption of saturated fat, trans fat, and dietary cholesterol raises low-density lipoprotein (LDL), or "bad" cholesterol, levels. This increases the risk of coronary heart disease. It also lowers high-density lipoprotein (HDL) or "good" cholesterol – causing a double whammy.
According to the National Heart, Lung, and Blood Institute of the National Institutes of Health, more than 12.5 million Americans have coronary heart disease, and more than 500,000 die each year. That makes coronary heart disease one of the leading causes of death in the United States.
The American Heart Association says although numbers for the intake of trans fatty acids in the United States exist, they are only estimates.
The FDA estimates that the average daily intake of trans fat in the U.S. population is about 5.8 grams for persons 20 years of age and older.
Senay says there is a lot of controversy around trans fats. In Denmark, products must be labels and there is a limit on how much trans fats manufacturers can put in foods. But in the U.S., health officials do not believe the substance requires that type of regulation.
The FDA's website says, "According to experts, eliminating trans fat completely from the diet would require such extraordinary dietary changes (e.g., elimination of foods, such as dairy products and meats that contain trans fatty acids) that eliminating trans fat could cause an inadequate intake of some nutrients and create health risks."
The agency does acknowledge the research by the Institute of Medicine of National Academies of Science, the national cholesterol education program, and the USDA, which has established a relationship between trans fat and an increased risk of coronary heart disease.
Citing this research, the FDA is requiring manufacturers of conventional foods and some dietary supplements to list trans fat on their labels. Food manufacturers have until January 1, 2006, to list trans fat on the nutrition label.
Senay says since the labeling policy does not take effect for a couple of years, you may not know if your food contains trans fats. One good hint is if the food contains hydrogenated or partially-hydrogenated oil, which indicates it has trans fat.
As an alternative to food with trans fat, look for foods made with mono and polyunsaturated fats, which do not raise LDL (or "bad" cholesterol). Such alternatives are olive oil, canola oil, soybean, corn, sunflower oils.
Senay says the United States does not have a recommended daily allowance of trans fats. However, the American Heart Association's nutrition committee "strongly advises that healthy Americans over age 2 limit their intake of saturated fat and trans fat to less than 10 percent of total calories." They go on to say, "Minimize trans fat intake. If you limit your daily intake of fats and oils to 5-8 teaspoons, you aren't likely to get an excess of trans fatty acids."