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Diet and Nutrition

Trans-Fatty Acids: One of the Bad Guys?

What's all this talk about trans-fatty acids? What are they? Where do you find them?

Hydrogenation is a process used by food manufacturers to make unsaturated fatty acids harder (e.g., when vegetable oil is made into stick or tub margarines). Hydrogenated fats are also less vulnerable to attack by oxygen and, therefore, less prone to rancidity.

A disadvantage of hydrogenation is that it adds hydrogens to unsaturated fats, making them more saturated. Consequently, the health benefits associated with unsaturated fats are lost in the process. Another disadvantage of hydrogenation is the change in structure of the unsaturated fats. During hydrogenation, some of the unsaturated fatty acids become trans-fatty acids (rather than the normally occurring cis-fatty acids). Trans-fatty acids have hydrogens on opposite sides of the carbon chain at the double bonds. This changed configuration affects the fatty acid's functions in the body.

Trans-fatty acids behave more like saturated fats rather than unsaturated fats. Research indicates that trans-fatty acids elevate LDL-cholesterol and lower HDL-cholesterol, raising the risk of heart disease. Epidemiological studies also suggest a relationship between trans-fatty acids and heart disease.

The Institute of Medicine recommends that your intake of trans-fatty acids should be as low as possible. So where do you find trans-fatty acids? Margarines, especially the harder forms, contain trans-fatty acids. However, snack chips, cakes, cookies, doughnuts, pastries, crackers, peanut butter, and deep-fried foods may contribute even more trans-fatty acids to the diet. By limiting your intake of these processed foods, you will control your intake of trans-fatty acids. Replacing both saturated fats and trans-fats with monounsaturated and polyunsaturated fats may be the best dietary strategy for combating heart disease.

All food labels must list the amount of trans-fat (number of grams) in one serving of the food item. Therefore, to increase marketability, many manufacturers have removed trans-fats from their products. So it is important to read labels to decide if a product is "trans-fat free" or not.

If a food is already prepared, you may not know if it contains trans-fat. To ensure that food eaten away from home is trans-free, some states and cities have passed laws to eliminate trans-fat from foods sold in bakeries, restaurants, and schools. If you are unsure of your local laws, you can ask the server or manager if the foods prepared in that establishment are trans-free.

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Last Reviewed: Jan 26, 2011

Bonnie J Brehm, PhD, RD Bonnie J Brehm, PhD, RD
Professor of Nursing
College of Nursing
University of Cincinnati