Trans fats show up in two places: naturally in small amounts in meat and dairy, and artificially in processed foods made with partially hydrogenated oils. While the U.S. banned manufacturers from adding partially hydrogenated oils to foods starting in 2018, trans fats haven’t disappeared entirely from the food supply. Knowing where they still hide helps you avoid a fat that raises your bad cholesterol, lowers your good cholesterol, and increases coronary heart disease risk by 23% for every 2% of daily calories it replaces.
Processed Foods That Still Contain Trans Fats
The FDA’s ban on partially hydrogenated oils removed the largest source of artificial trans fats from American grocery shelves. But “removed” doesn’t mean “eliminated.” Some products manufactured before full compliance deadlines worked their way through distribution until January 2021, and certain foods can still contain trace amounts of trans fat from other manufacturing processes. The foods most likely to carry residual trans fats fall into familiar categories:
- Baked goods: Commercially made cakes, pies, cookies, biscuits, sweet rolls, and donuts
- Fried foods: Anything fried and battered, including fast food items
- Frozen foods: Frozen dinners, pizza, ice cream, frozen yogurt, milkshakes, and pudding
- Solid fats: Vegetable shortening and some stick margarines
- Snack foods: Crackers, microwave popcorn, and packaged snack mixes
- Refrigerated dough: Pre-made biscuit, crescent roll, and pizza dough
- Non-dairy creamers: Powdered and liquid coffee creamers
Street food and restaurant food deserve special attention. Baked and fried items from restaurants, bakeries, and street vendors often contain industrially produced trans fats, particularly in countries without strict bans. Even in the U.S., small and independent restaurants may use older frying fats or imported ingredients that haven’t been reformulated.
The Labeling Loophole You Should Know About
A product labeled “0g trans fat” can still contain trans fat. FDA rules allow manufacturers to round down to zero if a serving contains less than 0.5 grams. That sounds trivial, but it adds up fast. If you eat three or four servings of a food that contains 0.4 grams per serving, you’ve consumed over a gram of trans fat from a product that technically advertises none.
The fix is checking the ingredient list, not just the nutrition panel. Look for the words “partially hydrogenated” followed by any type of oil (soybean, cottonseed, palm). If that phrase appears anywhere in the ingredients, the product contains some amount of trans fat regardless of what the label says. Vegetable shortening is another term that historically signaled trans fat content, though many shortening products have been reformulated.
Trans Fats in Meat and Dairy
Beef, lamb, and dairy products naturally contain small amounts of trans fats produced by bacteria in the stomachs of cows and sheep. The main one is called vaccenic acid. These natural trans fats typically make up a small fraction of the total fat in a glass of milk or a serving of butter, far less than what processed foods once delivered.
Whether these natural trans fats carry the same health risks as the artificial kind is still an open question. USDA-funded feeding studies found that vaccenic acid had no effect on LDL (bad) cholesterol levels. Its impact on HDL (good) cholesterol was inconsistent across studies, with one finding a modest 5.2% decrease in HDL among women with higher body weight but no significant effect in leaner women. A systematic review from the USDA’s Nutrition Evidence Systematic Review concluded there’s limited evidence for a substantial biological difference between natural and industrial trans fats, but that comparison was based on studies where people consumed natural trans fats at seven to ten times their normal intake. At the small amounts people actually eat from meat and dairy, the risk appears far lower than from industrial sources.
How Frying Creates Trans Fats
Even without partially hydrogenated oils, the frying process itself generates small amounts of trans fats. Heating vegetable oil to high temperatures causes some of its fatty acids to change shape into trans configurations. The World Health Organization notes this creates trans fat concentrations of up to 2 to 3%, which is low compared to the 25 to 45% concentration found in partially hydrogenated oils. Still, restaurants that reuse frying oil repeatedly or maintain very high temperatures may push those numbers higher. Foods deep-fried in fresh, non-hydrogenated oil contain far less than foods fried in older or partially hydrogenated frying fats.
Why Trans Fats Are Worse Than Saturated Fat
Trans fats do something no other dietary fat does: they raise LDL cholesterol and lower HDL cholesterol at the same time. Saturated fat raises LDL too, but it doesn’t suppress HDL. In a controlled feeding study, swapping saturated fat for trans fat dropped participants’ HDL cholesterol by 21%, from an average of about 73 mg/dL down to roughly 57 mg/dL. That’s a significant shift in the wrong direction for heart health.
Trans fats also impair the function of the cells lining your blood vessels, making arteries less flexible and more prone to plaque buildup. Research from Harvard’s School of Public Health, drawing on combined evidence from multiple studies, found a 23% higher risk of coronary heart disease for each 2% of daily calories coming from trans fat. For someone eating 2,000 calories a day, 2% is just 4 grams, an amount that was easy to reach with a single fast food meal before the ban.
How to Minimize Your Intake
Read ingredient lists on packaged foods, not just the front label. Any mention of “partially hydrogenated” oil means trans fat is present. Choose liquid cooking oils (olive, canola, avocado) over solid fats like shortening or stick margarine. Soft tub margarines have largely been reformulated to remove trans fats, but checking the label is still worthwhile.
When eating out, fried foods remain the biggest wild card because you can’t check the oil. Chain restaurants in the U.S. have largely switched to trans-fat-free frying oils, but smaller establishments and international restaurants may not have. Baked goods from small bakeries can also be a source, especially if recipes still call for shortening.
Pay attention to serving sizes on the label. A bag of crackers might list a serving as five crackers, but if you eat fifteen, you need to triple whatever trans fat content is listed. With the 0.5-gram rounding rule, those zeros on the nutrition panel can quietly become meaningful amounts over the course of a day.