What Are Trans Fats and Why Are They So Bad?
What do cream-filled doughnuts, frozen chicken pot pie, and store-bought frosting have in common?
Aside from perhaps being tasty treats or occasional indulgences, these foods also commonly contain trans fats.
While most aspects of nutrition are up for debate, the experts agree on this one: Trans fats are harmful to our health.
So why are trans fats bad for us, and why do experts warn us to eat them at our own risk? Trans fats can have waist-widening and artery-clogging consequences.
Trans fats have been called “stealth fats” because this type of fat can be hidden in foods that you may regularly eat.
Reading food labels may not always protect you since gray areas in laws mean they might not be fully identified.
Here’s what you need to know about foods that contain trans fats.
What is Dietary Fat?
Dietary fats consist of different arrays of “fatty acids,” and these fatty acids are found in foods like animal products as well as plant foods like beans, nuts, seeds, and even (in very small amounts) vegetables.
Trans fats are a unique type of fat, and to understand trans fats, it’s helpful to learn a bit about the biochemistry of fat.
Fat, or fatty acids, differ based on their chemical structure. There are different types of saturated fats, such as palmitic acid and stearic acid found in animal products like meat, dairy, and some vegetable oils, like coconut and palm.
Unsaturated fatty acids, known as the “good” kind of fat, are divided into monounsaturated and polyunsaturated types, which differ in their chemical bond structure. These are found more predominantly in plant foods like olives, avocados, nuts, and seeds.
Many foods contain a range of fatty acids, both saturated and unsaturated. So while a steak is considered to be high in saturated fat, it also has a small amount of unsaturated fatty acids.
And while an olive contains mostly unsaturated fat, it also has small amounts of saturated fat. Foods are generally categorized by the type of fat that is the most prevalent, even if they contain a blend.
What’s the Difference Between Unsaturated, Saturated, and Trans Fats?
A fat’s chemical makeup affects its physical and culinary characteristics. Saturated fats are more solid at room temperature, whereas unsaturated fats are more liquid and thus more susceptible to going rancid faster.
That’s why you can open a bottle of sesame oil that’s been in the cupboard for too long and immediately notice that it smells “off.”
Enter trans fats, which were largely the invention of food manufacturers.
What are Trans Fats?
Trans fats are a certain type of fatty acid that has what is known as a “trans” chemical structure, which is basically a reconfiguration of the atoms.
Trans fats have been altered to be more like saturated fat — and therefore more solid at room temperature. Plus, they last longer before going rancid, saving money.
Trans fats do occur naturally in some foods, such as meat and milk products, but they entered the food system in a big way in the early 1900s, when the chemical process of hydrogenation was invented.
It was long recognized that limiting animal fats and including more vegetable fats could support heart health and healthy cholesterol levels.
But vegetable oils spoil faster, so researchers developed a method of altering a fat’s chemical structure to solidify it and extend its shelf life.
Vegetable shortenings were the result of hydrogenation. By the 1960s, hydrogenated vegetable oil was in widespread use by food manufacturers, fast-food restaurants, and even home cooks.
This new, chemically altered oil not only had beneficial cooking properties (like flakier pie crusts), it solved a major problem in the food industry. Baked and fried goods now had a longer shelf life.
Plus, it was cheap — but everything has a price.
Why Are Trans Fats Bad for You?
As research on hydrogenated vegetable oils accumulated, their downsides became apparent. Trans fats can increase LDL (“bad”) cholesterol, says James Marin, R.D., a dietitian based in Los Angeles, California.
Trans fat also lowers the “good” HDL cholesterol, whose function is to mop up excess fat lingering in the blood. Removing trans fats from your diet can promote heart health.
By the 1990s, the World Health Organization started warning us to reduce intake of trans fats, and, in 2006, the New York City Health Department banned the use of trans fats in restaurants.
The U.S. Food and Drug Administration (FDA) followed suit in 2015, determining that partially hydrogenated oils, which were the primary source of artificial trans fats in processed foods, were no longer be considered safe for use in human food.
Why Do Some Foods Still Contain Trans Fats?
Trans fats were officially banned in 2015, but changes like that take time. “The problem is, trans fats are still found in foods even though the Food and Drug Administration took partially hydrogenated oils off the list of ingredients that are ‘generally recognized as safe’ back in 2015,” explains Krista Maguire, R.D., C.S.S.D., and senior nutrition manager at BODi. “The FDA gave food manufacturers until 2018 to comply with a ruling that all food prepared in the US must not include partially hydrogenated oils, unless approved by the FDA.”
So that’s why you still hear about these unhealthy fats — and why you still need to be on the lookout for them.
How to Find Hidden Trans Fats
The good news is that, theoretically, the Nutrition Facts label on most products will tell you whether a food contains trans fats or not.
The bad news is that the labels aren’t foolproof. Loopholes in government regulations mean that trans fat can still be in foods with a Nutrition Facts label that claims 0 g trans fat.
That’s because manufacturers are allowed to round amounts down, so a food that has 0.49 g trans fats per serving would say 0 g trans fats on the label. “Some food producers reduce serving sizes so that they can dupe the consumer into thinking it’s a healthy, trans-fat-free option,” says Haynes.
That means if a realistic portion size of that hidden source of trans fat is three servings (versus whatever the label claims you should consider to be a single serving), you could ingest 1.5 g of trans fats from a food that claims to contain zero.
When it comes to trans fats, there appears to be no safe amount (especially when it comes to heart health), so even small amounts are a concern. This is why trans fats have been banned.
To complicate efforts to avoid these fats, the FDA has made a special exception, allowing food companies to petition to use partially hydrogenated oils as additives and in other specific applications.
What About Natural Trans Fats?
Even if a food contains no partially hydrogenated oils, trans fats are still required to be listed on labels, because they are naturally found in food from some animals, such as cows and goats.
Would natural trans fats be a safer form than the chemically modified varieties? Maybe, but maybe not.
“Most of the research suggests that natural sources of trans fat may not hurt your health if consumed in small amounts,” says Haynes. “But if these foods are consumed in large amounts, then there may be negative cardiovascular effects similar to those from the man-made partially hydrogenated oils found in packaged and processed foods.”
That means you shouldn’t swap beef tallow or lard for shortening and margarine.
Common Foods High in Trans Fats
Ready to clear your diet of trans fats? Find out which common foods high in trans fats might be in your pantry or fridge right now.
Since the FDA started sounding warning bells about trans fats, food manufacturers and fast-food chains have voluntarily reduced their use of partially hydrogenated vegetable oils.
But trans fats are still used in many products, such as:
- Doughnuts (including the cream filling)
- French fries and other fried foods
- Fried chicken
- Frozen dinners
- Frozen pie crusts
- Margarine (In “What Works as a Butter Substitute?“, you can also find margarine and shortening swaps.)
- Packaged baked goods like pastries, doughnuts, cakes, and cookies
- Peanut butter (especially those labeled “no-stir” or “peanut spread”)
- Pizza crusts
Where Do Trans Fats Hide in Foods?
Beyond the foods you know to contain trans fats, there are plenty more where partially hydrogenated fats lurk, including but not limited to:
- Coffee creamer
- Cream-filled candies
- Creamy puddings
- Crunchy Asian noodles
- Frozen burgers, beef sausages, and beef hot dogs
- Granola bars
- Ground beef
- Ice cream
- Meat jerky sticks
- Microwavable meals like breakfast sandwiches or pastry tarts
- Microwave popcorn
- Packaged pancake batter
How to Avoid Trans Fats
Many of the traditional trans fat-filled foods, like margarine, reformulated their recipes and no longer contain them.
But be vigilant, advises Haynes: “Since your label may read ‘0 trans fats’ but still may contain them, always look at the ingredients list. If you read an ingredients label and see any type of hydrogenated vegetable oil or partially hydrogenated vegetable oil, that’s a red flag that trans fats are in that food.”
Thankfully, there’s an easy way to avoid sneaky trans fats.
“The very best way to avoid trans fat is to eat mostly whole, unprocessed plant foods,” says Marin. To eliminate trans fats, avoid eating junk food, fast food, and processed foods, and cut out or minimize animal products.
“Ditch most packaged foods, and opt for fruits, veggies, nuts, seeds, beans, and lean protein,” recommends Haynes.
Trans fats do not have a place in a healthy diet. By choosing a diet rich in whole, unprocessed foods like the Ultimate Portion Fix nutrition program, you’ll avoid these harmful fats.
When you do choose to eat processed or packaged foods that potentially could contain trans fats, be sure to read the label, as no amount of trans fats is a healthy amount.