Trans Fats

Medically Reviewed by Poonam Sachdev on May 07, 2024
Written by Marijke Vroomen Durning, RN, Elaine Magee, RD, MPH, Amy Gopal
7 min read

You eat several kinds of dietary fats in your diet. Some are good for you, others not so much. Trans fats, or trans-fatty acids, are a type of fat that fall into the “unhealthy” category because they can increase your risk of heart disease, and they have no known health benefits.

Trans fats exist in two general forms.

One type of trans fat occurs naturally in small amounts in some meat and dairy products. This type of trans fat forms in the guts of some animals and is present in food that comes from them.

The other type, which is the main source of trans fat in processed foods, is artificially added as partially hydrogenated oil. This type of trans fat is produced by adding hydrogen to vegetable oils to make them more solid.

Some companies use trans fats because processed foods last longer on a grocery or pantry shelf. Also, trans fats are cheap to make, can be reused in restaurant fryers, and can add flavor and texture to some foods.

Trans fats vs. saturated fats

According to the U.S. FDA and the American Heart Association, trans fats pose a greater risk for heart disease than saturated fats.

However, it's not a good plan to switch from consuming trans fats to saturated fats. They're both linked to heart disease. You should limit saturated fat to about 5%-6% or less of your daily intake of calories, which comes to 13 grams if you eat 2,000 calories a day.

Some ways to limit your intake of saturated fat are to:

  • Stick to a diet rich in foods including fruits, vegetables, low-fat dairy products, and unprocessed foods
  • Limit the intake of sweet drinks and foods as well as red meat
  • Use substitutes for butter
  • Use unhydrogenated oil for cooking
  • Opt for foods made with unhydrogenated oils instead of partially hydrogenated oils

Consuming trans fats, especially those from hydrogenated oils, increases your LDL cholesterol. This is the “bad” type of cholesterol that clogs and hardens your arteries, leading to a higher risk of blood clotting or stroke. High LDL cholesterol levels can also increase your risk of developing heart disease, which is the No. 1 cause of death in men and women in the U.S.

Other conditions related to trans fats may include:

Diabetes. Trans fats are associated with a higher risk for type 2 diabetes.

Low weight for newborns. Trans fat intake during pregnancy may be linked to the birth of babies with lower birth weight.

Cancer. Consuming trans fats can increase the risk of prostate cancer and colorectal cancer. We need more studies to confirm this.

There's no real nutritional benefit of hydrogenated oil in your diet. Doctors recommend avoiding trans fats as much as possible.

Eating trans fats can cause weight gain. Some research shows that animals that eat trans fats gain weight, particularly belly fat. Experts don’t know exactly why, but it may have something to do with that fat collecting in the abdomen.

The FDA banned companies in the U.S. from adding partially hydrogenated oils to foods beginning in 2015. It also requires trans fats to be listed on Nutrition Facts labels.

However, if a product has 0.5 grams or less of trans fats per serving, companies can market it as having 0 grams of trans fats; so it's important to be aware of foods that may contain it.

Many other countries have banned trans fats, but not all. For example, margarines sold in the U.S. can't have added trans fats, but those sold in other countries may still have it.

The FDA says trans fats may still be present in small amounts in some packaged foods, such as:

  • Crackers, cookies, cakes, frozen pies, and other baked goods
  • Snack foods (such as microwave popcorn)
  • Frozen pizza
  • Vegetable shortenings and some stick margarines
  • Coffee creamer
  • Refrigerated dough products (such as biscuits and cinnamon rolls)
  • Ready-to-use frostings

Check the ingredient list to see if it mentions partially hydrogenated oils.

Trans fats in fast food

Some fast-food chains have stopped using trans fats.

Check the nutritional information for the restaurants you visit the most. Nutrition and fat facts are often available on a restaurant's website, menus, flyers, or posters.

Watch out for trans fats in these types of fast foods:

  • Pastries, pie crust, and biscuits
  • Breaded or fried chicken and seafood
  • French fries
  • Desserts
  • Breakfast foods

Be sure to check nutrition labels for trans fat amounts. If it’s not listed, check the ingredient list for the words "partially hydrogenated oil" or "shortening." If they are in the first three ingredients for a particular food product, and the food product contains quite a bit of total fat, chances are there is a fair amount of trans fats in that food.

If a nutrition label isn’t clear, you can figure out the amount of hidden trans fatty acids by doing a little math:

  • Step 1: Add up the grams of saturated, monounsaturated, and polyunsaturated fats.
  • Step 2: If the number from step 1 is less than the total amount of fat on the label, you can assume the missing grams are trans fats.

Here’s an example using a nutrition label for frozen waffles that says one 4-inch plain frozen waffle has 3.17 grams of total fat. 

Step 1: Add:

  • 0.54 grams of saturated fat
  • 1.62 grams of monounsaturated fat
  • 0.73 grams of polyunsaturated fat

This gives us a total of 2.89 grams

Step 2: Take the 3.17 grams of total fat listed at the top of the label. Subtract the 2.89 grams of the listed fats. This leaves 0.28 grams of fats that are unaccounted for. These are the trans fats.

How much trans fat can I have per day?

It’s hard to avoid all trans fats, especially since manufacturers don’t have to list them if they make up less than 0.5 grams per serving.

Dietary needs change depending on your age, size, health issues, and more, so it’s hard to say exactly how much trans fat a person can have. On average, adults should consume between 1,600 to 3,000 calories per day. The World Health Organization says that people who consume 2,000 calories per day should have less than 2.2 grams of trans fats per day.

Most of your fats should come from monounsaturated fats, which help reduce LDL cholesterol levels. These are mainly found in olives and peanut oil. Other healthy fat options include omega-3 fatty acids, which you can find in fish and nuts and some other food sources:

Naturally occurring oils. Instead of eating products with artificial oils, try natural ones such as olive oil, corn oil, or canola oil to avoid trans fat.

Plant-based meat alternatives. Eating a few vegetarian meals per week can help you avoid trans fats. Meat alternatives have come a long way, to include much more than just tofu. A goal of companies such as Beyond Meat and Impossible Foods is to make plant-based meats taste just like the real thing. However, go for foods that are lower in sodium, as some plant-based alternatives have equal or higher levels of sodium than real meat.

Plant-based dairy alternatives. Instead of traditional nondairy coffee creamer for your morning cup of coffee, try oat milk or almond milk creamer. These options have zero trans fats, and some brands have made special barista-inspired products centered around making your coffee taste great.

Trans fats are unhealthy fats that can increase your risk of heart disease. Although the FDA requires U.S. companies to list trans fats on Nutrition Facts labels, if a serving contains less than 0.5 grams of trans fats, it can be marketed as not having any. To learn if there are trans fats in a product, add up the amounts of saturated fat, monounsaturated fat, and polyunsaturated fat, and see if the total equals the amount of total fat on the label. If there is a difference, there are hidden trans fats in the product.

How do you avoid trans fats?

The best way to avoid trans fats is to read food labels, avoid processed and fried foods, and eat more whole foods, such as vegetables, fruits, beans, and grains.

Does butter have trans fats?

Butter does have some trans fat, which is naturally occurring because it’s a dairy product from animals. Even if a butter nutrition label doesn’t list trans fat, you can calculate it. One example label shows that 1 tablespoon of salted butter has 11.52 grams of total fat. Of this, there are:

  • 7.29 grams of saturated fat
  • 2.98 grams of monounsaturated fat
  • 0.43 grams of polyunsaturated fat

Adding those three types of fat totals 10.7 grams. That means there are 0.82 grams of fat unaccounted for on the label, which is trans fat.

How are trans fats made?

Some trans fats are natural and come from animal products, while artificial trans fats come from a process of adding hydrogen to vegetable oil. This is called partially hydrogenated oil.

Are any trans fats OK?

It is best to avoid any trans fats if you can. They have no health benefits.