Some fats are good for you, some fats are bad. Trans fats? They're in the latter category. "Trans fats are man-made fats where manufacturers take what should be a liquid-at-room-temperature fat, transform it into a solid-at-room-temperature-fat," says Robin Foroutan, MD, RDN, HHC, a spokesperson for the Academy of Nutrition and Dietetics. "The benefit to this is that then the fat becomes more shelf-stable and resistant to spoiling." According to the Food and Drug Administration, the primary dietary source of trans fats in processed foods are partially hydrogenated oils (PHOs).
Foroutan adds that trans fats do exist naturally in tiny amounts in red meat and dairy, but these types have differently-shaped molecules, so they have a different effect on the body.
How Are Trans Fats Different?
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You might be wondering how they're different from other fats and why they're bad for you. "Trans fats create a lot of inflammation in your body," she explains. "And they contribute pretty significantly to heart disease. Part of what they do is lower good cholesterol and increase bad cholesterol. Our cell membranes are made out of lipids, and we get those lipids from the kinds of fats we eat. And so if you're eating trans fats, you add little kinks to your cell membranes. That disrupts cell function, and makes it so that cells can't communicate with one another as well." Trans fats can also increase your risk of stroke and developing diabetes.
In 2015, the Food and Drug Administration determined that PHOs were not "Generally Recognized as Safe" (GRAS) and banned manufacturers from adding them to foods. The deadline for compliance was June 18, 2018, but the FDA extended the date to January 1, 2020, for certain uses.
While most processed foods shouldn't contain trans fats due to the FDA guidelines, some might sneakily still have them. That's why it's important to read the nutrition labels carefully. Food labels have a section for trans fats, but even if it says zero trans fats, you might not be in the clear.
"The food companies are allowed to label their products as having zero trans fats as long as the product contains half a gram per serving or less of trans fats," Foroutan says. In addition, to look at the label, you should also look at the ingredient list. Words to look out for are "hydrogenated" or "partially hydrogenated," which basically mean trans fats.
Take a look at this list below of foods that traditionally have trans fats, so you know to pay extra close attention to those labels.
Shortening or Margarine
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A lot of these were traditionally made with PHOs. Now, there is margarine made without trans fats, but check the label to see if you're in the clear. They might still have a tiny amount of trans fat, falling under the 0.5 grams or less loophole. Instead, try olive oil, if the recipe allows.
Before you dig into that bag of donuts or box of cookies, take note. The Cleveland Clinic says that most cake and cookie mixes say zero trans fat, but actually have trans fat content that's under 0.5 grams. That can add up if you are decorating the cake with frosting that also contains less than 0.5 grams of trans fats.
"Creamers are also a big source," Foroutan says. "Be on the lookout. Just because it's non-dairy does not make it healthy."
The Cleveland Clinic has a handy rule for discovering "sneaky" amounts of trans fats: "If a food can last in your pantry for weeks without going stale, trans fat might be keeping it fresh." Crackers might fall under this category.
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Restaurants and fast food joints might fry their food in oil that have trans fats. Some cities have banned trans fats in restaurants, like New York City, but it differs from state to state and city to city. "If you're using trans fats for frying for instance, you don't have to change the oil as often," Foroutan says. "So fried food is a big possibility for where you might be getting trans fats from because at restaurants, it's not labeled."
Ever wonder why frozen pizzas can go from icy to crispy? You can thank trans fats, according to The Cleveland Clinic. You might be better off making a homemade version—more work, but at least you can control what you put on it (and in it).