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Trans fatty acids (trans fats) have gained quite a reputation. But they deserve the bad rap. Identifying foods high in trans fats and reducing or even eliminating those foods from your diet is an important way to keep your heart healthy. In fact, it takes such a small amount of these so-called trans fats to negatively impact cardiovascular health that the American Heart Association recommends cutting back on foods that contain trans fats.

What Are Trans Fats?

The term “trans fat” refers to vegetable oils (made up of mostly unsaturated fats) that have had hydrogen added to them. This process is known as hydrogenation or partial hydrogenation.

Partial hydrogenation of vegetable oils is done to make fats more solid at room temperature, to increase their shelf life by keeping their flavor stable over longer periods of time, and to guard against spoilage. Margarines, shortening, the oils used to cook fast food French fries, and commercial baked goods are all examples of foods that can contain trans fatty acids.

The Harm of Trans Fats

Trans fats not only raise LDL ("bad") cholesterol levels (as saturated fats also do), they also lower levels of HDL ("good") cholesterol. Trans fat also increases blood triglyceride levels. Several studies have examined the effects of trans fats on cholesterol levels and heart disease risk.

Food Labels and Trans Fats

Because of the strong evidence showing that trans fats increase the risk of heart disease, the US Food and Drug Administration (FDA) requires food manufacturers to list trans fat amounts on the nutrition facts panel of the food label.

Under this rule, trans fat is listed as a separate line item under saturated fat. However, if a food contains less than 0.5 grams of trans fat per serving, food manufacturers may list it as containing 0 grams of trans fat. So, a food may contain trans fats in small amounts, but still be considered “trans-fat free.”

The only way to be sure that a food is completely free of trans fat is to carefully inspect the ingredient list for the phrases “partially hydrogenated” or “shortening." These terms indicate that the food contains trans fats. This also makes it important to pay attention to serving sizes, since eating just 2 servings of a food could boost the trans fat content to a higher level.

Which Foods Contain Trans Fats?

In addition to reading the Nutrition Facts panel, here are some ways for identifying foods that contain trans fats:

• Partially hydrogenated oils is listed as an ingredient
• Certain groups of foods tend to be high in trans fats, including:
  • Deep fried foods, such as donuts and French fries
  • Foods that sit on the shelf, but still stay fresh such as cookies, chips, crackers, and baked goods
  • Frozen foods, especially frozen meals and pizzas
  • Foods that are solid at room temperature, such as margarine that is solid, but made from oil
• Meat and dairy products—small amounts of trans fat are found naturally in these foods

Since the FDA's rule went into effect, many food companies have eliminated trans fats from their products. But because food labels are only required on packaged foods, foods served at restaurants and bakeries are still likely to contain partially hydrogenated vegetable oils or shortening. Some cities in the US have banned restaurants from using trans fats. For example, restaurants in New York City are now trans-fat-free. Some large fast food companies, like Kentucky Fried Chicken, have also made the switch.

Lowering How Much Trans Fat You Eat

Use the following strategies to cut down on your trans fat intake:

• Eat less of the following foods that are high in trans fat:
  • Margarine, particularly stick margarine—Use olive oil, canola oil, liquid, or trans-fat-free tub margarines instead.
  • Cookies, cakes, and pastries
  • Crackers, cereals, and snack foods containing partially hydrogenated vegetable oil
  • French fries and other fried foods
  • Donuts
• If you enjoy margarine on your morning toast, use tub margarine that contains less trans fat and is low in saturated fat and use a smaller amount.
• Check the list of ingredients. If partially hydrogenated oils appear on the list, the food contains trans fats, even though it may be a small amount.
• Foods high in trans fats tend to be snack foods, so fill up on whole grains, vegetables, lean meats, and fish. Choose fruits or low-fat dairy products for snacks.
• Limit saturated fats. Saturated fats and trans fats often go hand in hand, so limiting your intake of saturated fats should automatically lower your trans fat intake.