By Dena McDowell, MS, RD

Trans fatty acids, also known as trans fats, are fats that are formed when vegetable oils are hardened into margarine or shortening. Other foods including fried foods like French fries, donuts, cookies, pastries, and crackers contain these artery-clogging fats. Trans fats are popular with food manufacturers because they reduce cost, extend storage life of products, and can improve flavor and texture.

Trans fats are unhealthy

A diet high in trans fats increases your blood levels of "bad" cholesterol (low density lipoprotein or LDL) and decreases your levels of "good” cholesterol (high density lipoprotein or HDL). High levels of LDL and low levels of HDL cholesterol increase your risk of heart disease, which is the leading cause of death among Americans. In addition to heart disease, research has shown that trans fatty acids have many adverse effects on health, increasing the risk of cancer, diabetes, and obesity, as well as compromising your immunity and negatively affecting your reproduction and lactation.

Chose your dietary fats wisely

All food companies are required to list trans fat on nutrition labels. However, there is no upper safety limit recommended for the daily intake of trans fat. The Food and Drug Administration (FDA) has only said that "intake of trans fats should be as low as possible”.

• Check the Nutrition Facts panel. Choose foods that are lower in saturated fat, trans fat, and cholesterol. For saturated fat and cholesterol, keep in mind that 5% of the daily value (%DV) or less is low and 20% or more is high. (There is no %DV for trans fat.)
• Choose alternative fats. Replace saturated and trans fats in your diet with monounsaturated and polyunsaturated fats. These fats do not raise LDL cholesterol levels and have health benefits when eaten in moderation. Sources of monounsaturated fats include olive and canola oils. Sources of polyunsaturated fats include soybean oil, corn oil, sunflower oil and foods like nuts and fish.
• Choose vegetable oils. Vegetable oils (with the exception of coconut and palm kernel oils) and soft margarines (liquid, tub, or spray) are better choices because the amounts of saturated fat, trans fat, and cholesterol are lower than what’s in solid shortenings, hard margarines, and animal fats (including butter).
• Consider fish. Most fish are lower in saturated fat than meat. Some fish—such as mackerel, sardines and salmon—contain omega-3 fatty acids, which may offer protection against heart disease.
• Choose lean meats. Skinless poultry, lean beef and pork (with the visible fat trimmed off) are good dietary choices that can reduce your trans fats. Instead of frying, try baking, grilling or broiling them.
• Ask before ordering. When you’re eating out, it’s a good idea to ask about the fats used in the preparation of your food. In addition, ask for high-fat condiments to be put on the side. Request that your vegetables be steamed or sautéed instead of fried.
• Watch calories. Don't be fooled! Fats are high in calories. All sources of fat contain nine calories per gram, making fat the most concentrated source of calories. By comparison, carbohydrates and protein have only four calories per gram.

Total Fat, Saturated Fat, Trans Fat, and Cholesterol Content Per Serving*
Product	Common Serving Size	Total Fat g	Sat. Fat g	%DV for Sat. Fat	Trans Fat g	Combined Sat. & Trans Fat g	Chol. mg	%DV for Chol.
French Fried Potatoes± (Fast Food)	Medium (147 g)	27	7	35%	8	15	0	0%
Butter**	1 tbsp	11	7	35%	0	7	30	10%
Margarine, stick†	1 tbsp	11	2	10%	3	5	0	0%
Margarine, tub†	1 tbsp	7	1	5%	0.5	1.5	0	0%
Mayonnaise†† (Soybean Oil)	1 tbsp	11	1.5	8%	0	1.5	5	2%
Shortening±	1 tbsp	13	3.5	18%	4	7.5	0	0%
Potato Chips±	Small bag (42.5 g)	11	2	10%	3	5	0	0%
Milk, whole±	1 cup	7	4.5	23%	0	4.5	35	12%
Milk, skim†	1 cup	0	0	0%	0	0	5	2%
Doughnut±	1	18	4.5	23%	5	9.5	25	8%
Cookies± (Cream Filled)	3 (30 g)	6	1	5%	2	3	0	0%
Candy Bar±	1 (40 g)	10	4	20%	3	7	<5	1%
Cake, pound±	1 slice (80 g)	16	3.5	18%	4.5	8	0	0%
*Nutrient values rounded based on FDA's nutrition labeling regulations. ** Butter values from FDA Table of Trans Values, 1/30/95. † Values derived from 2002 USDA National Nutrient Database for Standard Reference, Release 15. †† Prerelease values derived from 2003 USDA National Nutrient Database for Standard Reference, Release 16. ± 1995 USDA Composition Data.

For more information on which fats are healthy for you see the following articles from TheDietChannel: A Guide to Healthy Cooking Oils, Fat Facts: Fat Confusion Cleared Up and Healthy and Fat: 5 High Fat Foods You Should Not Avoid.