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Why shouldn't we eat trans-fats?

The FDA is expected to make a final ruling this week on trans-fats. Here's what you need to know about them.
/ Source: NBC News

The U.S. Food and Drug Administration is expected to issue its final ruling this week on trans-fats.

Advocates sued the FDA to force it to limit how much of the stuff we can eat — or at least how much can go into food.

Here are answers to your top five questions on trans-fats:

What are trans-fats?

Trans-fats or trans-fatty acids are made when a liquid oil is chemically processed to make it solid or semi-solid. It’s easier to work with, and the resulting product doesn’t go rancid as quickly as liquid oil. In baking, it makes a liquid oil work more like butter or lard, creating a smooth and tasty product. They show up on labels as “partially hydrogenated” oils.

Where are they found?

They’re found mostly in fried and baked goods, from doughnuts and biscuits to frozen pizza and stick margarine. Microwave popcorn and fast food often contain trans-fats. Small amounts of trans-fats are also found in meat and dairy products. And often foods that say they are “trans-fat free” in fact contain trans-fats.

One place you won’t find them is in New York City restaurants. New York banned trans-fats in 2006.

What do they do that’s bad?

They raise levels of LDL, the low-density lipoprotein or so-called bad cholesterol. This is the stuff that sticks to the inside of arteries, making them hard and inflexible, blocking blood flow and breaking off to cause heart attacks and strokes. They also raise the risk of diabetes.

What can I eat instead?

“Good” fats such as olive oil, canola oil, sunflower or safflower oil. “Use soft margarine as a substitute for butter, and choose soft margarines (liquid or tub varieties) over harder stick forms. Look for ‘0 g trans fat’ on the Nutrition Facts label and no hydrogenated oils in the ingredients list,” the American Heart Association advises. And, of course, the AHA and other groups recommend eating more fresh fruits and vegetables and whole grains and less of the fried and processed foods most likely to contain trans-fats.

Not butter or lard, by the way. Butter and lard both contain saturated fat, which also raises cholesterol. So do palm oil, coconut oil and cocoa butter. The FDA ruling would not affect use of butter or lard so you'll still need to check labels and ask about them in restaurants.

What will the FDA ruling do?

The FDA says trans-fats are no long “generally recognized as safe,” or GRAS, for short. Foods that are considered GRAS can be used and sold freely. If the FDA makes this determination permanent, companies will have to seek explicit FDA approval to use trans-fats in food.

You’re probably already seeing less trans-fat, anyway, as companies are moving to find substitutes. The Grocery Manufacturer's Association of America says food makers have lowered the amount of trans-fat in processed foods by 86 percent since 2003.