What Exactly Is Trans Fat, and Why Is It Bad for You?
Key takeaways:
Trans fat has a different chemical structure than other types of fats. Some foods have a small amount of naturally occurring trans fat, but most trans fat is artificially made.
Trans fats are associated with an increased risk of heart disease, oxidative stress and inflammation, and diabetes.
The FDA and WHO banned trans fats in 2015 and 2018, respectively. But it’s likely going to take until the end of 2023 (at least) for them to be removed from foods completely.
Table of contents
It can be hard to understand which types of fat are good or bad for you. One thing that all researchers agree on, however, is that trans fat is bad for you. This may not be the first time you’ve heard this — but what may be less clear is what trans fat is exactly, and why health experts recommend limiting it as much as possible.
What does trans fat mean?
The term “trans fat” refers to fat with a specific chemical structure. Trans fats have certain types of chemical bonds that differ from other types of fats. These unique bonds change the shape of the fat, as well as how your body reacts to it (more on this later).
Unlike other types of fats, most trans fats are artificially made. They’re formed when hydrogen is added to liquid vegetable oils to make the oils solid at room temperature. This not only makes the vegetable oils more stable (they don’t go rancid as quickly), but it also decreases the production cost of processed foods.
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For example, instead of using butter to make a flaky pie crust, companies are able to use these solid vegetable oils to get a similar texture at a cheaper cost.
Why are trans fats bad for you?
Your liver processes trans fats differently than other types of fats. Because of this, they affect your health differently, too. Trans fats are considered “bad” fats because they can:
Raise your LDL cholesterol (or “bad” cholesterol)
Lower your HDL cholesterol (or “good cholesterol”)
Increase your triglyceride levels (another type of fat that circulates in the blood)
The way that trans fat is processed in the body can increase your risk for:
Heart disease, specifically coronary artery disease and heart attacks
Stroke
Inflammation, which, in the long run, can damage tissues and raise your risk for chronic health conditions
According to the World Health Organization (WHO), trans fats are responsible for half a million premature deaths from coronary artery disease around the world each year.
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How much trans fat a day is considered bad for you?
There is no set amount of trans fat that is considered bad for you. But according to the WHO, some international experts recommend limiting trans fat to 1% of your daily calories. So if you eat around 2,000 calories per day, this would mean eating no more than 2 g of trans fat.
That said, when it comes to trans fat, the less you eat the better — especially if you have or are at risk for heart disease. Unlike other types of fat that support your health, your body doesn’t need trans fats to function. As you learned in the last section, you’re better off without this type of fat.
How do you know if a food contains trans fat?
On nutrition labels, you’ll see a row underneath total fat and saturated fat dedicated to trans fat.
In 2003, the FDA added an amendment to its labeling laws that said trans fats had to be declared on every nutrition label going forward. But there’s a caveat here: If the total amount of trans fat is less than 0.5 g, companies are allowed to round down. In other words, if a food contains 0.4 grams of trans fat, a food manufacturer can list trans fat as 0 g.
So, how do you really know if a food contains trans fats? You have to rely on the ingredient list. Certain words indicate the addition of trans fats, even if the label says zero. Watch out for the following ingredients:
Partially hydrogenated vegetable oils
Fully hydrogenated vegetable oils
Shortening
Margarine
Trans fats are found in the highest amounts in ultra-processed foods. While they can really be found in any types of food that are made with certain oils, some of the most common are:
Packaged desserts and pastries, including cookies and muffins, pie crusts, and ice cream
Processed breads, like pizza dough, hamburger buns, and crackers
Margarine and vegetable shortening
Pre-packaged mixes, like pancake mix, cake mix, and drink mixes
Fried foods, like fried chicken and chicken nuggets, French fries, and doughnuts
Packaged snacks, like crackers, chips, and microwave popcorn
How to limit trans fat in your diet
There are a few effective ways to limit trans fat in your diet. Here are four steps you can take:
Avoid highly processed foods.
Check nutrition labels and ingredient lists, and try to avoid any that have a measurable amount of trans fats or list hydrogenated or partially hydrogenated oils as an ingredient.
Limit your fast food intake. Many fast food restaurants use partially hydrogenated oils to deep fry, since it’s cheaper and more shelf-stable.
Opt for unsaturated or healthier fats, such as avocados, nuts, and olive oil. And to the extent possible, make fruits and vegetables, whole grains, and lean protein the focus of your diet.
The good news is that the FDA officially banned trans fats in the U.S. in 2015, and the WHO called for a worldwide elimination in 2018. Because of this, fewer foods have trans fats than in the past. However, companies were given a grace period to phase them out. Right now, it’s expected that they will be completely eliminated from foods by the end of 2023.
The bottom line
The benefits and risks of different dietary fats have long been debated. But one thing that experts agree on is: Trans fat is bad for you. While the FDA and the WHO have put regulations in place to ban trans fats by the end of 2023, read food labels and avoid hydrogenated and partially hydrogenated oils as much as possible. Similarly, avoiding ultra-processed foods, which often contain trans fats, can help.
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References
American Heart Association. (2017). Trans fats.
Dhaka, V., et al. (2011). Trans fats—sources, health risks and alternative approach - A review. Journal of Food Science and Technology.
Field, A. E., et al. (2007). Dietary fat and weight gain among women in the Nurses' Health Study. Obesity.
Kabagambe, E., et al. (2012). The relation between erythrocyte trans fat and triglyceride, VLDL- and HDL-cholesterol concentrations depends on polyunsaturated fat. PLOS One.
U.S. Food and Drug Administration. (2018). Final determination regarding partially hydrogenated oils (removing trans fat).
U.S. Food and Drug Administration. (2018). Small entity compliance guide: Trans fatty acids in nutrition labeling, nutrient content claims, and health claims.
World Health Organization. (n.d.). REPLACE trans fat.
World Health Organization. (2023). Five billion people unprotected from trans fat leading to heart disease.
