The nutritionally aware have long known that trans fats are bad news – too much of it in your diet can raise your risk for heart disease. And even though manufacturers have been required to list a products’ trans fats (in grams) in the nutritional information panel since 2006, many people out there still find the topic confusing. Here’s what you should know.

What is trans fat? Trans fat is vegetable oil that has been processed to reduce spoiling. Trans fat is used in packaged foods, especially snack foods, to give them a longer shelf life. 

Why is trans fat bad? “Both trans fats and saturated fats raise LDL, or bad cholesterol, but trans fats are a little more villainous, because they also reduce HDL, or good cholesterol. That dual effect raises the risk of heart disease,” says Cindy Moore, a dietitian and nutrition therapy director at the Cleveland Clinic Foundation.

Where are trans fats found? About one-fourth of all trans fats are naturally occurring and are found in the fat of meat and dairy products. The biggest source, however, comes from partially hydrogenated vegetable oil. Polyunsaturated fats, such as corn and safflower oil, when heated in the presence of hydrogen, create partially hydrogenated – or trans – fats that don’t go rancid as quickly, extending the shelf life of processed foods. Both shortening and margarine owe their existence to this process.

Fat facts. Unsaturated fats - monounsaturated and polyunsaturated – are beneficial when consumed in moderation. Trans fats and saturated fat (found in meat and dairy products) are not.

The numbers game. When you’re reading product labels for trans fats, remember that amounts under 0.5 grams, are listed as 0 grams. So some products will appear trans fat-free. “The amounts listed are per serving, though,” says Moore. “Small amounts of trans fats can add up, so consider portion size when you look at the ingredient panel.”

Removing Trans Fats From Your Diet

Eliminating trans fats completely would require extraordinary dietary changes, so make minimizing them your goal. Here are some ideas.   

At home:

  • Replace stick margarine with tub margarine, especially those labeled trans fat-free.
  • Use trans fat-free liquid oils, such as olive, canola or peanut oil instead of margarine or shortening.

At the supermarket:

  • Shop the perimeter of the store and choose lean meats, fruits and vegetables or low-fat or fat-free dairy and whole grain products. The inside aisles are home to convenience products that typically contain trans fats.
  • Read the ingredient lists on baked, frozen and other processed foods, and avoid those with higher amounts of hydrogenated or partially hydrogenated oil.
  • Shop at natural foods stores, such as Whole Foods Markets, that do not sell products with partially hydrogenated oils.
  • Go easy on snacks such as sweet rolls, chips and cookies; they are among the biggest culprits.

At a restaurant:

  • Eat fewer fried foods, which are usually fried in trans fat, and instead choose grilled meats and veggies, such as salads with grilled chicken and oil-based dressings.