Trans fats show up in two places: processed foods made with partially hydrogenated oils and, in much smaller amounts, the meat and dairy of grazing animals like cows, sheep, and goats. While the U.S. and many other countries have banned the main industrial source, some products still contain trace amounts, and certain foods slip under the labeling radar.
Processed Foods With Trans Fats
The biggest historical source of trans fats was partially hydrogenated oil, a manufactured fat created by pumping hydrogen into liquid vegetable oil to make it solid at room temperature. This process gave foods a longer shelf life and a desirable texture, but it also produced high concentrations of trans fats, sometimes making up as much as 60% of the fat in the product.
Foods that traditionally relied on partially hydrogenated oils include:
- Margarine and vegetable shortening, used as butter substitutes in home and commercial cooking
- Commercial baked goods like crackers, biscuits, pie crusts, cookies, and pastries
- Fried foods, especially from restaurants and street vendors that reused hydrogenated frying oil
- Refrigerated doughs such as canned biscuits and crescent rolls
- Non-dairy creamers and microwave popcorn, which used hydrogenated oils for texture and shelf stability
- Frozen pizza, packaged snack cakes, and ready-made frosting
In 2015, the FDA determined that partially hydrogenated oils are not safe for use in food. Manufacturers were required to stop adding them by mid-2018, with final distribution deadlines extending to January 2021 for certain products. Globally, nearly 60 countries now have best-practice elimination policies in effect, covering 46% of the world’s population. Still, in countries without bans, these oils remain common in commercial frying and baking.
Meat and Dairy Contain Small Amounts Naturally
Bacteria in the stomachs of ruminant animals (cows, sheep, and goats) naturally convert small amounts of unsaturated fat into trans fat. This means beef, lamb, butter, cheese, cream, and whole milk all contain some trans fat, though the concentrations are far lower than what processed foods once carried. In milk, trans fat makes up about 4 to 6% of total fat. Across the diet, roughly 85% of naturally occurring trans fat intake comes from dairy products and 15% from ruminant meat.
Whether these naturally occurring trans fats carry the same health risks as the industrial version is still debated. The amounts are small enough that most dietary guidelines don’t single them out the way they do industrial trans fats.
How Trans Fats Affect Your Body
Trans fats do something no other type of fat does: they raise your LDL (“bad”) cholesterol while simultaneously lowering your HDL (“good”) cholesterol. That double hit accelerates the buildup of plaque inside your arteries, increasing your risk of heart disease and stroke. Saturated fat raises LDL too, but it doesn’t suppress HDL the way trans fats do, which is why trans fats are considered uniquely harmful.
The Labeling Loophole to Watch For
In the U.S., a food can be labeled “0 g trans fat” if it contains less than 0.5 grams per serving. That means a product with 0.4 grams per serving technically qualifies for a “0 g” label. If you eat multiple servings, those fractions add up. This was a bigger concern before the ban on partially hydrogenated oils, but it still matters for imported products or older stock.
The most reliable way to check is to scan the ingredient list for the words “partially hydrogenated.” If any oil is listed as partially hydrogenated, the product contains some trans fat regardless of what the nutrition label says. Fully hydrogenated oils, by contrast, are a different process and do not contain significant trans fats, so the word “partially” is the key signal.
What Replaced Trans Fats in Processed Foods
After the ban, food manufacturers switched to several alternatives. Palm oil and palm kernel oil became popular replacements in baked goods and margarines because they’re naturally solid at room temperature without hydrogenation. High oleic versions of canola and sunflower oil took over in frying and snack production, offering stability at high heat without producing trans fats. Some manufacturers also turned to interesterified oils, which are chemically rearranged to mimic the texture of shortening.
These replacements eliminated the trans fat problem, but they’re not all nutritionally identical. Palm oil, for instance, is high in saturated fat. If you’re comparing products, checking the saturated fat line on the nutrition label gives you a more complete picture of what you’re eating now that trans fat numbers are often zero.
Where Trans Fats Still Hide
Even in countries with bans, a few situations can still expose you to trans fats. Imported packaged foods from countries without restrictions may contain partially hydrogenated oils. Restaurant and street food in parts of Asia, Africa, and Latin America often still use hydrogenated frying fats. And any food containing dairy fat or beef fat will have trace natural trans fats, though these are generally not considered a priority to avoid.
If you travel or buy imported snacks, checking ingredient lists for “partially hydrogenated” remains the simplest safeguard. In domestic grocery stores, the combination of the FDA ban and labeling rules means your exposure is likely minimal compared to what it was even a decade ago.