Facts About Trans Fats and Their (Not Necessarily Better) Replacement

Most of us know that trans fats are bad for our health. But what are trans fats? Are there trans fats in your foods? Can you create trans fats when you cook? And how can you avoid one common trans fat alternative that's not really an improvement?

Monica Reinagel, MS, LD/N, CNS
5-minute read
Episode #600
The Quick And Dirty
  • Some dairy products and meats contain small amounts of naturally-occuring trans fats but these are not thought to be a concern.
  • Partially hydrogenated oils were the primary source of trans fats in the modern diet, but are no longer used in U.S. food manufacturing.
  • Interesterified fats contain no trans fats but appear to pose many of the same health concerns.
  • Manufacturers are encouraged but not required to disclose the use of interesterified fats in food products.

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.

As of 2018, partially hydrogenated oils are no longer allowed in U.S. food products.

In 2015, the U.S. Food and Drug Administration decided that the man-made trans fats found in partially hydrogenated vegetable oils were unsafe for human consumption and gave food manufacturers three years to eliminate them from their products. As of 2018, partially hydrogenated oils are no longer allowed in U.S. food products.  

Long before the official ban was announced, however, trans fats had gotten a pretty bad reputation. Manufacturers were already moving 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?

Let's take a closer look and answer the questions:

  • What are trans fats?
  • Why are you supposed to avoid trans fats?
  • What are some alternatives to trans fats?

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. 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 your 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.

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.

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 not all trans fats are man-made. 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.

There’s research to show that natural trans fats aren’t as dangerous as 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, which are made made by adding hydrogen to a poly-unsaturated vegetable oil such as soybean or cottonseed oil. The hydrogen bonds to (or "saturates") some of the carbon molecules in the oil.

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're 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.

What have trans fats been replaced with? 

Although you will still see partially hydrogenated oils in products imported from other countries, U.S. food manufacturers are no longer allowed to use them. But what are they using instead?

Many 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.

A warning about interesterified fats

Another alternative that’s become more widespread is interesterified fat. Interesterification is a chemical process that converts liquid oils to solid fats by artificially rearranging the shape of the molecules.

Although interesterified fats contain no trans fats, I’m not at all convinced it's an improvement.

Haven’t we been here before? In fact, we have. Although interesterified fats contain no trans fats, I’m not at all convinced it's an improvement. 

Little is known about the safety or health effects of interesterified fats, but the few small studies we do have are not reassuring. Interesterified 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. So far, their use in food manufacturing is largely unregulated. As their use increases, public health researchers are calling for more research. 

In the meantime, it might be prudent to avoid foods made with interesterified fats—but this turns out to be easier said than done. Unfortunately, manufacturers are encouraged (but not required) to label interesterified fats in the ingredient list. As a result, they may be listed as ‘vegetable oils,’ ‘fully hydrogenated oils,’ ‘palm oil,’ ‘palm kernel oil,’ ‘high stearate,’ or ‘stearic rich’ fats. The types of packaged foods that are most likely to contain interesterified fats include:

  • Baked goods
  • Crackers and cookies
  • Icing
  • Biscuits and biscuit mixes
  • Microwave popcorn
  • Non-dairy replacements for things like butter and cheese

Packaged foods made only with butter, coconut oil, olive oil, or other specifically-identified oils are probably a safer bet. Safest of all? Homemade treats where you control the ingredients.

Citations +

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.