What Are Trans Fats?

You know they’re bad for you. Now, a few things you might not know about trans fats.

Monica Reinagel, MS, LD/N, CNS
5-minute read
Episode #69

What exactly is a trans fat? Most people aren’t exactly sure, but they’ve gotten the general idea that trans fats—whatever they are—are bad for you. In recent years, manufacturers have scrambled to get the trans fats out of their products—or at least make it look as if they have. But have you ever wondered what they’ve replaced them with?

Today, we’ll take a closer look at trans fats: what they are, where you find them, why you’re supposed to be avoiding them, and what your alternatives are.

What are Trans Fats?

First, what exactly is a trans fat? I don’t want to spend too much time on the chemistry, even though it’s really kind of interesting. For those who want to delve deeper, I’ll include some links in the show notes. Suffice it to say that a trans fat is an unsaturated fat that has acquired all the bad habits of a saturated fat, and adopted a few new ones, just for spite.

Like saturated fats, trans fats raise your LDL (or “bad”) cholesterol. To make matters worse, they also lower you HDL (or “good”) cholesterol. Plus, trans fat molecules are harder for the body’s enzymes to take apart, so they are more prone to ride around in your arteries, looking for trouble to get into.

Because of all this, experts now consider trans fat to be a bigger factor in heart disease than saturated fat. And although formal charges have yet to be filed, trans fat is also being eyed for various other crimes, including acting as an accomplice in the development of Alzheimer’s, cancer, diabetes, and infertility.

What Foods Contain Trans Fats?

It may surprise you to learn that dairy products and some meats contain small amounts of naturally-occurring trans fats. But these are not the ones that we’re concerned about. First of all, they don’t add up to very much. Secondly, there’s research to show that these natural trans fats aren’t as dangerous as the man-made ones.

Nor do you need to worry about accidentally creating trans fats in your own kitchen. Though it’s true that heating oils can cause some of the fat molecules to change into a trans configuration, it takes a lot more heat and/or pressure than you are likely to employ while making dinner. 

The trans fats that we’re primarily concerned about are the ones in partially- hydrogenated vegetable oils.

The trans fats that we’re primarily concerned about are the ones in partially- hydrogenated vegetable oils. The hydrogenation process, which really caught on in the 1960s, transforms liquid oils like corn or soybean into solid fats, like shortening. It seemed like a great idea at the time.

Hydrogenated vegetables oils are more stable than liquid oils, and that extends the shelf life of products. Solid fats produce a better texture in baked goods and snacks. Hydrogenated oils are way cheaper than butter, and they are lower in saturated fats! Pretty soon, hydrogenated oils were in everything. Of course, then we realized that trans fats were even worse for you than saturated fats. Oops.

How to Avoid Trans Fats

Now that we know better, reducing the amount of trans fats in our food supply has become a priority for health experts and consumers. The situation became more pressing for manufacturers in 2006, when new rules went into effect, requiring that the amount of trans fats in packaged foods be listed on the nutrition facts label.

Unfortunately, many manufacturers have taken advantage of a labeling loophole. If a food contains less than half a gram of trans fat per serving, the manufacturer is allowed to round that down to 0. A manufacturer might even manipulate the serving size in order to keep the amount of trans fat per serving under half a gram. That’s why you’ll often see foods labeled 0 grams of trans fat, and then find partially hydrogenated oil listed in the ingredients.

If you want to avoid trans fats, you can’t rely on the nutrition facts label.

Half a gram may not seem like much, but if you eat several servings of this kind of thing, it can start adding up. If you want to avoid trans fats, you can’t rely on the nutrition facts label. You need to check the ingredient list for partially hydrogenated oils.

Of course, not all foods have labels. Prepared foods most likely to contain trans fats are bakery items like cookies, pastries, doughnuts, cupcakes, and anything with frosting. With deep fried foods like French fries, onion rings, egg rolls, and fried chicken, it depends on what kind of oil they’re frying it in.

New York City recently passed a law banning trans fats in restaurants and some other cities are considering similar laws.  In the meantime, some big chains such as Taco Bell, have voluntarily removed trans fats from their food. Restaurants that have switched to trans-fat-free oil usually make a pretty big to-do about it. If they’re not saying anything, I’d suspect that they’re using hydrogenated oils.

What Are Trans Fats Being Replaced With?

As more and more manufacturers and restaurants move away from hydrogenated oils, the question becomes: What are they using instead?

Many manufacturers are using a blend of liquid vegetable oil and palm oil.  Like hydrogenated oils, palm oil is solid at room temperature, so it makes products more shelf stable and it provides that crisp texture we’ve come to know and love. It’s also relatively cheap and contains no trans fat. It is high in saturated fat, however.

Another alternative that’s starting to show up in ingredient lists is inter-esterified fat. Inter-esterification is a chemical process which converts liquid oils to solid fats by artificially rearranging the shape of the molecules. Haven’t we been here before? In fact, we have.

Inter-esterified fats appear to have the same doubly negative effect on cholesterol levels as trans fats. To add insult to injury, they may also increase blood sugar levels. Although inter-esterified fats contain no trans fats, I’m pretty sure it’s a step in the wrong direction and I’m hoping it won’t catch on.

As a wise man once said “Those who cannot remember the past, are condemned to repeat it.”

My quick and dirty tip is to avoid foods made with hydrogenated oils and inter-esterified fats. The best way to do this is by reading ingredient labels and limiting your intake of commercial baked goods and deep-fried foods. When you’re cooking at home, I recommend that you use butter, palm oil, or coconut oil instead of shortening. Just keep your intake of total and saturated fat within reason, of course. You might also want to read my article on coconut oil.


Post your questions and comments on my Nutrition Diva Facebook Page or send me a tweet on Twitter. I answer a lot of listener questions in my free weekly newsletter, so if you’ve sent a question my way, be sure you’re signed up to receive that.

Have a great day and eat something good for me!


Chemistry of Trans Fats

Trans Fat: Cholesterol Double Whammy (Mayo Clinic)

Not All Trans Fats Are Man-Made

Does Cooking with Oil Create Trans Fats? (Nutrition Over Easy Blog)

What Are Inter-esterified Fats and Should We Be Worried About Them?

About the Author

Monica Reinagel, MS, LD/N, CNS

Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes' most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation's leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.