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Nutrition

Get excited about nutrition, and learn as you go with these information-packed resources on a wide variety of nutrition-centric topics! Our bistroMD experts review the importance of the macronutrients protein, fat, and carbohydrates, as well as how to make them work most efficiently for you.

What Is Trans Fat? Foods, Risks & Expert Guidelines

While the low-fat diet craze is outdated, perhaps one type of fat deserves to stay in the past… Find out the major risks of trans fats, including its negative impact on heart health.

What Is Trans Fat? Foods, Risks & Expert Guidelines


Rarely do dietitians recommend completely avoiding a specific food or ingredient because, generally, most things are ok in moderation. However, the exception might just be trans fat. 

Trans fat has already been banned in other countries for many years, and the US is not too far behind. Learn once and for all why consuming trans fat is harmful to health.

What Is Trans Fat?

Sometimes called trans-fatty acids, trans fat is a form of unsaturated fat. There are natural and artificial forms, with animal products supplying the ruminant or natural form. 

Natural Trans Fat

Naturally occurring trans fat is formed when bacteria in animal stomachs digest grass. The most well-known naturally occurring trans fat is conjugated linoleic acid (CLA), which is interestingly believed to be healthful and is even sold as a supplement. 

Research also shows that this type of trans fat is hardly harmful, so meat-eaters rest easy!

Artificial Trans Fat

Conversely, artificial trans fat - sometimes called industrial trans fat or partially hydrogenated fat - is quite detrimental to health. In 2013 the Food and Drug Administration (FDA) actually determined that artificial trans fat is no longer 'Generally Recognized as Safe' (GRAS). 

This type of trans fat is man-made and literally created via an industrial process that adds hydrogen to liquid vegetable oils to make them more solid. Thus, the primary source of artificial trans fat is partially hydrogenated oils that are present in processed vegetable oils and packaged/processed foods.

Sources of Artificial Trans Fat

• Partially hydrogenated vegetable oils (vegetable oil and as an ingredient in other foods)
• Vegetable shortening
• Some varieties of microwaveable popcorn
• Some margarines
• Many fried fast foods (fried chicken, battered fish, hamburger, french fries, noodles)
• Bakery products (cakes, cookies, pastries, doughnuts, muffins, etc.)
• Non-dairy coffee creamers
• Others, but in smaller amounts:

• Corn and potato chips
• Sausages and meat pies with flaky crusts
• Sweet pies
• Pizza
• Canned frosting
• Crackers

Additionally, keep in mind that food products with less than 0.5 grams can technically be labeled as having 0 grams of trans fat, so this list might actually be longer.

Trans Fats and Health Risks 

Many studies have linked consumption of trans fat with cardiovascular disease, elevated bad cholesterol levels (LDL), and reduced good cholesterol levels (HDL). However, more recently, it is associated with an increased risk of stroke, type 2 diabetes, obesity, and systemic inflammation, which can lead to literally all health complications.

Heart Disease

Numerous observational and experimental studies associate trans fat consumption with an increased risk of heart disease, mainly because they seem to increase bad cholesterol and decrease good cholesterol, which leads to increased plaque buildup.

Diabetes

Although research is not yet completely conclusive, one large study demonstrated that those who consumed the most trans fat were at a 40% higher risk of developing type 2 diabetes. Furthermore, numerous animal studies purport that large amounts of trans fat impair glucose and insulin function. 

Any time glucose and insulin regulation are disrupted, the risk for obesity increases as well.

Inflammation

Two major studies show that trans fat increases inflammatory markers like hs-CRP, especially when they replace other nutrients. This means that someone who consumes very little healthy fats and some trans fat is worse off than someone who consumes trans fat but also eats plenty of healthy fats like omega-3 fatty acids in fatty fish and olive oil, avocados, and nuts and seeds. 

Systemic inflammation is problematic because it is a primary root cause of many chronic illnesses like heart disease, metabolic syndrome, stroke, high blood pressure and cholesterol, diabetes, autoimmune conditions, arthritis, and just about every other one.

Cancer

Although this area of research is greatly lacking, one big study linked intake of trans fat before menopause to an increased risk of breast cancer after menopause. Researchers believe that trans fat directly impairs cell walls, which has implications for how cells divide. 

Since cancer is a disease of cell division, it is very plausible that this is an accurate association.

Update on Trans Fat Ban

Given that trans fat is almost solely associated with negative health outcomes, it is a wonder why food companies still utilize them. However, artificial trans fat is inexpensive, long-lasting on shelves, and simple to use. 

Furthermore, the fast-food industry continues to use trans fat for frying because it can be used many times in commercial fryers. However, each use of this oil increases the trans fat content, making it that much more harmful.

It was not until the 1990’s that scientists started recognizing the deleterious effects of trans fat and this spurred a campaign to reduce consumption and eventually ban the industrial form altogether.

Here is a timeline of the most important milestones:

• 1999 - FDA proposes that trans fat be added to food nutrition labels

• 2002 - The Institute of Medicine recommends that people consume as little trans fat as possible

• 2003 - Denmark becomes the first country to eliminate trans fat from foods

• 2004 - The Center of Science in The Public Interest petitions the FDA to prohibit the use of partially hydrogenated oils

• 2006 - Trans fat labeling becomes mandatory on nutrition food labels

• 2008 - The California governor signs legislation to phase out artificial trans fats from CA restaurants

• 2013 - FDA announces its preliminary decision that partially hydrogenated oils are no longer considered generally safe (GRAS)

• 2018 - FDA officially bans trans fat, but products that contain it can still be distributed until they are used up (meaning trans fat can still be in products that will be sold in 7 years…)

The Takeaway

There are two types of trans fat- ruminant and industrial- but only the latter is associated with poor health, especially cardiovascular disease. High consumption of this man-made fat disrupts cellular function and greatly increases the risk for other chronic diseases like diabetes in addition to heart disease and associated complications. 

Although the FDA has made moves to completely ban trans fat, it is still in some food products, either because they contain less than 0.5 grams or because they were created before 2018 and can still be distributed. Although eating an occasional bakery product that has minimal trans fat is ok, it’s best to try and avoid trans fat altogether. 

By 2030, no one should need to worry about trans fat, because it should be completely eradicated! And if a food product still contains some trans fat, just know that it was likely developed before 2018… Props to the shelf life, but it is more of a chemical product and much less edible food at that point.

References:

Trans Fats. American Heart Association. Reviewed March 23, 2017. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/fats/trans-fat.

Coyle D. 7 Foods That Still Contain Trans Fats. Healthline. Written October 29, 2018. https://www.healthline.com/nutrition/trans-fat-foods

Leech J. What Are Trans Fats, and Are They Bad for You? Healthline. Written July 30, 2019. https://www.healthline.com/nutrition/why-trans-fats-are-bad.

Sydney Lappe's Photo
Written By Sydney Lappe, MS, RDN. Published on February 18, 2022. Updated on April 26, 2022.

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