Trans fat is a type of dietary fat that’s solid at room temperature. It’s often added to processed foods to improve texture and lengthen shelf life, but of all the different types of fats found in food, trans fat is by far the worst for heart health.
In 2015, the U.S. Food and Drug Administration (FDA) removed trans fat from its list of substances “Generally Recognized as Safe” (GRAS) and later enacted a ban on the use of trans fat in food products and food service establishments.12
Yet despite these restrictions, trans fat—which the World Health Organization (WHO) calls a “deadly food compound”—can still make its way onto your plate. And since no more than 1% of your total daily calories should come from trans fat, consuming even small amounts can harm your heart health.
What Makes Trans Fat Different From Other Dietary Fats?
There are two different types of trans fats. The first type is trans fat that’s naturally found in animal-based foods like meat and dairy products. The second type is industrial trans fat, which refers to trans fat that is synthetically created and then added to foods or used for food preparation methods like frying.3
Research on the negative health effects of trans fat has focused primarily on the industrial trans fats that are added to foods.3 It’s still not clear whether naturally occurring trans fat is as detrimental to heart health as man-made trans fat.4
Industrial trans fat has a unique chemical structure that’s formed through a process called partial hydrogenation. During partial hydrogenation, hydrogen gets added to a fatty acid and shifts the placement of its chemical bonds. This altered chemical structure impacts the fat’s texture, making it solid instead of liquid at room temperature. This process also increases the fat’s melting point and helps to extend its shelf life.5
If you’ve ever heard of ‘partially hydrogenated oils,’ then you’ve heard of trans fat—the two are synonyms.
Many countries, including Denmark, Switzerland, Canada, Brazil, Peru, and Turkey (among others) also restrict the use of trans fat in their food.42 Some estimates report that Denmark’s efforts to remove trans fat from its food supply has resulted in a 50% reduction in deaths caused by heart disease over the last two decades.6
Health Effects of Trans Fat
Whereas unsaturated fats—like those found in olive oil, nuts, and avocado—can help lower “bad” LDL cholesterol and raise “good” HDL cholesterol, trans fat has the opposite effect in humans. It increases harmful LDL cholesterol and decreases healthier HDL cholesterol levels in the blood.7
Over time, higher levels of LDL cholesterol can clog arteries, increasing the risk of heart attacks and strokes.8 Trans fat has also been linked to higher blood pressure levels and regularly eating even small amounts of trans fat has repeatedly been associated with a greater risk of developing heart disease.910
Studies conducted in mice suggest that trans fat may promote inflammation in the body and cause the liver to store more fat, a key risk factor for non-alcoholic fatty liver disease, or NAFLD.3
Trans fat’s negative effects may extend to the brain, as well. A recent observational study found that people with higher levels of trans fat circulating in their blood were more likely to be diagnosed with dementia or Alzheimer’s disease, suggesting that greater consumption of trans fat could potentially promote cognitive decline.11
Recommended Daily Intake
It’s recommended that dietary fats make up anywhere from 20-35% of calories consumed.12 Only a fraction of those fats should come from saturated fat, the type of dietary fat that can promote the buildup of harmful plaque in arteries.13 For example:
- The USDA recommends that saturated fats comprise no more than 10% of your total daily calories. That equates to up to 22 grams of saturated fat daily on a 2,000-calorie diet.14
- The American Heart Association (AHA) takes a stricter stance, recommending that no more than 6% of total daily calories come from saturated fats. That equates to no more than 13 grams of saturated fat per day on a 2,000-calorie diet.13
A much smaller percentage of fat consumed should come from trans fat. The United States Department of Agriculture’s 2020-2025 Dietary Guidelines for Americans recommends that trans fat consumption be “as low as possible without compromising the nutritional adequacy of the diet.”14
Other organizations provide more specific recommendations. For example, the WHO recommends that no more than 1% of total daily calories come from trans fat. On a standard 2,000-calorie diet, that’s no more than 2.2 grams of trans fat daily.15
Sources of Trans Fat
Though it has technically been eliminated from the food supply, industrial trans fat can still show up in our food thanks to a regulatory loophole. Any food with less than 0.5 grams of trans fat per serving can list 0 grams of trans fat on its packaging.4
While that may not sound like much, even small amounts of trans fat can negatively affect your health. Many people don’t stick to just one serving of food, either. Eating a few helpings of a snack with 0.4 grams of trans fat per serving could cause someone to eat more trans fat than is recommended for the whole day— in just one sitting.
Common sources of industrial trans fat include:16
- Packaged snacks like cookies, chips, and crackers
- Fried foods
- Fast food
- Baked goods like pies and cakes made with stick margarine or shortening
- Frozen foods, including dinners, pizzas, and ice creams
- Non-dairy creamers
Other ingredients like cake frostings, processed meats, and breakfast staples (such as pancake mixes and biscuits) may also contain trans fat.
How To Reduce Intake
Since manufacturers aren’t allowed to include more than 0.5 grams of trans fat per serving in their products, you’ll always see 0 grams in the trans fat line on a nutrition panel. However, if you see the words ‘partially hydrogenated oil’ or ‘partially hydrogenated vegetable oil’ in a product’s ingredients list, that’s an indication that it contains trans fat.
Always check nutrition labels and do your best to avoid products that contain any partially hydrogenated oils.
Here are some additional ways to reduce your trans fat intake:
- Minimize your consumption of fried and battered foods, since frying oils often contain trans fat
- Use non-hydrogenated, heart-healthy oils like olive and avocado oil instead of shortening or margarine when cooking or baking at home
- Reduce your intake of high-fat animal foods like butter, lard, red meat, pork, cream, and cheese
- Enjoy homemade sweets over packaged treats, as store-bought and packaged doughnuts, cookies, and pies are more likely to contain trans fat
- Ask restaurants what type of oils they use to prepare food
- Check large chain restaurants’ menus online to see which oils they use to prepare or fry food
- Try to reduce your consumption of ultra-processed foods, including salty snacks and frozen dinners
A Quick Review
Trans fat is among the worst ingredients for heart health thanks to its ability to raise harmful LDL cholesterol and lower healthier HDL cholesterol. Over time, eating a diet rich in trans fat can raise your risk of cardiovascular complications, including heart attacks and strokes.
Though the FDA has taken steps to significantly limit the amount of trans fat in our food supply, the harmful ingredient can still be found in small amounts in ultra-processed products like packaged snacks, baked goods, and fried foods.
The best way to avoid trans fat is to read through ingredients lists on nutrition labels. If “partially hydrogenated oil” or “partially hydrogenated vegetable oil” are among the ingredients, that’s an indication that the product contains trans fat.
Focus on eating a balanced diet rich in fruits, vegetables, whole grains, nuts, seeds, legumes, lean proteins and unsaturated fats for optimal heart health.
