Trans fat shows up in two places: processed foods made with partially hydrogenated oils and, naturally, in meat and dairy from animals like cows, sheep, and goats. While the U.S. banned the main artificial source in 2020, trans fat hasn’t disappeared entirely from the food supply.
Processed Foods With Trans Fat
For decades, food manufacturers relied on partially hydrogenated oils (PHOs) to give products a longer shelf life and a desirable texture. These oils were the primary source of artificial trans fat in the diet. The classic offenders include:
- Commercial baked goods: cakes, cookies, pies, and doughnuts
- Shortening and stick margarine
- Microwave popcorn
- Frozen pizza
- Refrigerated dough like biscuits and canned rolls
- Fried foods: french fries, fried chicken, and other deep-fried items
- Nondairy coffee creamer
The FDA revoked the “generally recognized as safe” status of PHOs in 2015 and set a final compliance date of January 1, 2021, giving manufacturers time to reformulate. As of December 2023, the regulatory revocation is fully in effect. Most major brands have already switched to alternatives like high oleic sunflower oil, palm oil, or blends designed to mimic the texture and stability that PHOs once provided.
That doesn’t mean every product on every shelf is completely free of artificial trans fat. Imported foods, smaller manufacturers, and products with long shelf lives may still contain trace amounts. Globally, progress has been uneven: as of 2023, only 53 countries had best-practice policies in place to eliminate industrial trans fat.
The Labeling Loophole
U.S. labeling rules allow manufacturers to print “0 g” of trans fat on the Nutrition Facts panel if a serving contains less than 0.5 grams. That means a product can technically contain trans fat and still say zero on the label. If you eat multiple servings, those small amounts add up.
The most reliable way to check is to scan the ingredient list for the words “partially hydrogenated” followed by any type of oil. If it’s listed, the product contains some artificial trans fat regardless of what the label says. This matters less now that PHOs are banned in the U.S., but it’s still worth knowing for imported products or older stock.
Natural Trans Fat in Meat and Dairy
Bacteria in the digestive systems of cows, sheep, and goats naturally convert fats from grass and other feed into small amounts of trans fatty acids. These are called ruminant trans fats, and they’re present in every product made from these animals: beef, lamb, butter, cheese, whole milk, and cream.
The amounts are relatively small. Milk fat contains about 4 to 6% trans fat, and ruminant fat in general tops out around 6%. The dominant type is vaccenic acid, which is structurally different from the artificial trans fats created during industrial hydrogenation. Because these natural trans fats exist at low levels, removing all of them from the diet would only reduce total trans fat intake by about 0.5% of daily calories.
Why Trans Fat Matters for Your Health
Trans fat does something unusual that other dietary fats don’t: it raises LDL (“bad”) cholesterol and lowers HDL (“good”) cholesterol at the same time. Most unhealthy fats only do one or the other. This double effect on your cholesterol ratio is what makes trans fat particularly harmful for heart health.
Quantitative reviews of human studies show that for every 1% of daily calories replaced by industrial trans fat instead of healthier unsaturated fat, LDL cholesterol rises and HDL cholesterol drops in a consistent, dose-dependent pattern. The practical translation: even small, regular amounts of artificial trans fat shift your cardiovascular risk upward. Estimates suggest that eliminating just the natural ruminant trans fat from the diet (which accounts for a small share of intake) could reduce cardiovascular disease risk by roughly 1.5 to 6%.
Fast Food and Restaurant Frying
Fast food chains once relied heavily on partially hydrogenated oils for deep frying because those oils resisted breaking down after repeated use at high temperatures. Most major chains have since switched to high oleic sunflower oil, palm oil, or similar alternatives that stay stable during frying without producing significant trans fat.
One thing to be aware of: when frying oils are reused over many days, trace amounts of trans fat can form through heat-driven chemical changes, even in oils that started with none. This is a minor source compared to the old PHO-based frying, but it means deep-fried foods from any restaurant are never completely trans-fat-free. Smaller or independent restaurants without corporate reformulation mandates are more likely to use older oil types or reuse oil longer.
How to Minimize Your Intake
Since the U.S. ban, your exposure to artificial trans fat is far lower than it was a decade ago. The remaining practical steps are straightforward. Read ingredient lists on packaged foods, especially imports, and avoid anything listing partially hydrogenated oils. Choose liquid cooking oils (olive, canola, avocado) over solid fats when cooking at home. Limit deep-fried foods from restaurants where you can’t verify the oil type. For natural trans fat in dairy and meat, the amounts are low enough that moderate consumption isn’t a major concern for most people.