The Problem with Trans Fats, Vegetable Oils, & Seed Oils

If necessity is the mother of invention, then this is true for the origin of artificial trans fats. In the early 20th century, trans fats became a convenient way to provide a more stable and solid form of unsaturated fats in food products in order to extend their shelf life and prevent foods from spoiling. Once coveted by food manufacturers and consumers, health experts now agree that trans fats are harmful to our health and should be avoided when possible. However, there is still some confusion about what types of fats are healthy and whether vegetable oils in general, often hailed as the healthier alternative to trans fats, are safe to consume.

The History of Trans Fats

In 1901, German chemist Wilhelm Normann found that adding hydrogen (hydrogenation) to vegetable oil resulted in a soft, solid form of the vegetable oil, which is usually liquid at room temperature. So novel was his discovery that Normann received a patent for it in 1903, and in 1911 Proctor & Gamble developed the first commercial vegetable shortening of its time, Crisco, a semi-solid hydrogenated vegetable oil (trans fat) used in baked goods to make them lighter, flakier, and softer.


Hydrogenation of food products gained momentum, especially during World War II, when there were shortages of dairy butter and oil and food rationing was essential. Margarine, a cheap butter-substitute originally derived from beef fat, was reformulated with cheap trans-fat vegetable oils. The idea that food products, such as Crisco and margarine, were “made from vegetables” fostered the belief that trans-fat products and vegetable oils were healthy and good for you. The fact that they were also inexpensive and flavor enhancing contributed to their commercial success.

In the 1950s questions concerning the health risks associated with natural saturated fats emerged. Ancel Keys, an American physiologist who led the now discredited “Seven Countries Study” that examined the link between dietary fat and cardiovascular disease, concluded that the saturated fats found in natural butter, eggs, whole milk, cheese, and red meat were harmful to the heart and should be avoided. As saturated fats were deemed unhealthy and a public health concern, synthetically produced unsaturated fats from vegetable oils and trans fats continued to rise until the 1990s, when overwhelming data showed that artificial fats were the true public health emergency and not the natural fats found in plants and animals.

Banning Trans Fats in Food Products

Trans fats are now known to be associated with several chronic health conditions and disease processes such as cardiovascular disease, diabetes, chronic fatigue, inflammatory disease, allergies, poorer outcomes during pregnancy, obesity, and cancer, to name a few. As early as the 1950s, many scientists were vocal about the potential health risks of these types of artificial fats. As the food industry denied the harm with these fats, continued studies in the 1980s and 1990s showed serious health risks with trans-fat consumption. A landmark study in 1993 in The Lancet opened the floodgates to the health risks and by the 2000s, health organizations around the world started to regulate the use of trans fats in foods. In the United States in 2006, the FDA finally required that Nutrition Fact labels declare trans fats and in January of 2020, food manufacturers in the US were no longer allowed to sell food products containing trans fats. The US is not the only country worldwide to ban industrial-made trans fat. In April of 2021, the European Union set regulatory limits on trans fat in foods, allowing trace amounts less than 2 grams of trans fat per 100 grams of fat. Other countries, including Canada, have also followed suit in banning or limiting trans fat in manufactured food products.

Vegetable Oils: An Unhealthy Alternative

With the trans-fat ban in the US, vegetable oils have become more commonplace. Though less toxic than trans fat, conventional vegetable oils can still pose serious risks to our health. These oils are ubiquitous in most foods that Americans eat and account for an estimated 15–20% of all calories we consume. Vegetable oils are sourced from various seeds, legumes, and plants, often with a chemical solvent in the production process (some healthier oils are made without solvents). Vegetable oils are made from seed oils, which most commonly include soybean oil, sunflower oil, corn oil, safflower oil, peanut oil, canola oil, rice bran oil, castor oil, rapeseed oil, cottonseed oil, and grapeseed oil. Some vegetable oils are made with the same hydrogenation process as trans fats in order to get a more spreadable consistency. Currently foods with these trans-fat vegetable oils can legally be produced if there are fewer than 0.5 grams of trans fat per serving.

There is another health concern with vegetable oil consumption. Due to the high omega 6 fatty acids found in vegetable oils, this creates an imbalanced ratio of omega 6 fatty acids to omega 3 fatty. Before the advent of modern vegetable oils in the mid 1800s, most ratios were 1:1. Now it is common to see ratios of omega 6 to omega 3 at 20:1 and this poses significant health risks over time.

Vegetable oils also have an overabundance of linoleic acid which is harmful in higher amounts, and vegetables oils oxidize when cooking thus creating dangerous free radicals.

Studies now show that most vegetable oils contribute to the same health problems that caused the banning of trans fats. These health problems include cardiovascular disease, cancer, inflammatory disorders, autoimmune disorders, gut health issues, and lung disease like asthma.

Wiseman Health Take-Home Advice

Because trace amounts of trans fats appear in common foods we eat, it’s important to recognize the foods that contain unhealthy vegetable oils and consume or use healthier oils instead.

  • In recent years there has been a broader public awareness that all “fats” are not created equal and that there are “good fats” and “bad fats.” A guiding principle to go by is that “good fats” are found in naturally-derived foods such as avocados, wild-caught fish, and nuts, and “bad fats” are found in artificial food products like chips, processed-packaged foods like microwave popcorn, desserts, etc.
  • Unfortunately, most processed foods and restaurant foods contain vegetable oils. Some common foods that contain vegetable oil include: oat milk, ice cream, pre-packaged nuts and snacks, energy bars, bottled salad dressing, refrigerated dough (biscuits and rolls) and frozen foods, and baby formula.
  • Avoid seed oils when possible. The most common include soybean oil, sunflower oil, corn oil, canola oil, rice bran oil, safflower oil, peanut oil, castor oil, rapeseed oil, cottonseed oil, and grapeseed oil.
  • Consume or use healthier non-seed oils in foods or when cooking. The three safest non-seed oils are olive oil (extra virgin), coconut, and avocado oil.  Coconut oil is the best for cooking due to its stability when heated. Avocado oil is another great oil for cooking and has the highest smoke point, so it is extremely stable under high-heat conditions. Olive oil is a healthy oil but avoid heating it over 250 degrees Fahrenheit because it will begin to oxidize at this point and become more harmful.
  • Grass-fed butter and ghee, a type of clarified butter, are also healthier alternatives to cook with or consume.
  • Look for these key words on nutrition labels that alert you the item contains vegetable seed oil: vegetable oils, trans fats, hydrogenated oils, hydrogenated vegetable oils, partially hydrogenated oils, and any of the seed oils named above.
  • Avoid vegetable oils when eating out. It can be difficult to know what kinds of oils are served in your food when dining out. Unless stated clearly, you can assume most establishments use the cheapest and most unhealthy seed-derived vegetable oils. Many restaurants do use vegetable oil alternatives like avocado oil or coconut oil as part of their overall healthier approach, but if not, you can also ask your server at any restaurant to substitute an unhealthy vegetable oil with something healthier such as butter, ghee, animal fat, olive oil, coconut oil, and/or avocado oil.
  • To find restaurants that use healthy oils and fats, use this helpful website:

Editor’s Note: This content was created by our Wiseman Health content and writing team, without the influence of artificial intelligence engines. Our goal is to be your trusted source for natural health and medical information. This article was originally published on February 23, 2024 and has since been updated.

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