Trans fat is double trouble for your heart health

Trans fat increases your "bad" cholesterol and lowers your "good" cholesterol. Find out more about trans fat and how to avoid it.

By Mayo Clinic Staff

Trans fat is considered the worst type of fat you can eat. Unlike other dietary fats, trans fat — also called trans-fatty acids — raises your "bad" cholesterol and also lowers your "good" cholesterol.

A diet laden with trans fat increases your risk of heart disease, the leading killer of adults. The more trans fat you eat, the greater your risk of heart and blood vessel disease.

Trans fat is so unhealthy that the Food and Drug Administration has recently prohibited food manufacturers from adding the major source of artificial trans fat to foods and beverages.

The FDA expects that this move will prevent thousands of heart attacks and deaths every year. But, as the regulation takes effect, some products with added trans fat may still be available.

Here's some information about trans fat and how to avoid it.

What is trans fat?

Most trans fat is formed through an industrial process that adds hydrogen to vegetable oil, which causes the oil to become solid at room temperature.

This partially hydrogenated oil is less likely to spoil, so foods made with it have a longer shelf life. Some restaurants use partially hydrogenated vegetable oil in their deep fryers, because it doesn't have to be changed as often as do other oils.

Some meat and dairy products have a small amount of naturally occurring trans fat. It's not clear whether this naturally occurring trans fat has any benefits or harm.

Trans fat in your food

The manufactured form of trans fat, known as partially hydrogenated oil, may be found in a variety of food products, including:

  • Baked goods, such as cakes, cookies and pies
  • Shortening
  • Microwave popcorn
  • Frozen pizza
  • Refrigerated dough, such as biscuits and rolls
  • Fried foods, including french fries, doughnuts and fried chicken
  • Nondairy coffee creamer
  • Stick margarine

How trans fat harms you

Doctors worry about added trans fat because it increases the risk for heart attacks, stroke and type 2 diabetes. Trans fat also has an unhealthy effect on your cholesterol levels.

There are two main types of cholesterol:

  • Low-density lipoprotein. LDL, or "bad," cholesterol can build up in the walls of your arteries, making them hard and narrow.
  • High-density lipoprotein. HDL, or "good," cholesterol picks up excess cholesterol and takes it back to your liver.

Trans fat increases your LDL cholesterol and decreases your HDL cholesterol.

If the fatty deposits within your arteries tear or rupture, a blood clot may form and block blood flow to a part of your heart, causing a heart attack; or to a part of your brain, causing a stroke.

Reading food labels

In the United States if a food has less than 0.5 grams of trans fat in a serving, the food label can read 0 grams trans fat.

Products made before the FDA ban of artificial trans fats may still be for sale, so check to see if a food's ingredient list says partially hydrogenated vegetable oil. If it does, that means the food contains some trans fat, even if the amount is below 0.5 grams.

This hidden trans fat can add up quickly, especially if you eat several servings of multiple foods containing less than 0.5 grams a serving.

How low should you go?

Trans fat, particularly the manufactured variety found in partially hydrogenated vegetable oil, appears to have no known health benefit. Experts recommend keeping your intake of trans fat as low as possible.

What should you eat?

Foods free of trans fats aren't automatically good for you. Food makers may substitute other ingredients for trans fat that may not be healthy either. Some of these ingredients, such as tropical oils — coconut, palm kernel and palm oils — contain a lot of saturated fat.

Saturated fat raises your total cholesterol. In a healthy diet, about 20% to 35% of your total daily calories may come from fat. Try to keep saturated fat at less than 10% of your total daily calories.

Monounsaturated fat — found in olive, peanut and canola oils — is a healthier option than is saturated fat. Nuts, fish and other foods containing unsaturated omega-3 fatty acids are other good choices of foods with healthy fats.

Feb. 13, 2020 See more In-depth

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