Trans Fats

What are trans fats?

Trans fats or trans-fatty acids are a form of unsaturated fat, which comes in both natural and artificial forms. 

Natural trans fats are present in the meat and dairy of cud-chewing animals (such as cattle, sheep, and goats) when bacteria in these animals’ stomachs digest grass. These naturally occurring trans fats are not harmful to health and may actually reduce the development of different chronic diseases.

foods with trans fats


On the other hand, artificial trans fats, also known as industrial trans fats or partially hydrogenated fats, are hazardous to health. These fats are mainly formed during hydrogenation, a process in which hydrogen is added to vegetable oils to form a semi-solid product known as partially hydrogenated oils, to lengthen the shelf life of foods. Some restaurants use these oils for deep-frying as they are repeatedly used and do not have to be changed as often as other oils. These oils are also found in a variety of food products, including:

  • Snacks, e.g. potato, corn, tortilla chips
  • Fried food, e.g. French fries, doughnuts, fried chicken
  • Baked food, e.g. cakes, cookies, pie crusts, crackers that contain shortening
  • Others: coffee creamer, stick margarines, frozen pizza crusts

How do artificial trans fats affect your health?

Your body does not need or benefit from artificial trans fats. Instead, eating these fats increases your risk of health problems:

  • Cardiovascular diseases: Trans fat increases your LDL (bad) and lowers your HDL (good) cholesterol. High LDL along with low HDL levels can cause cholesterol to build up in your arteries (blood vessels). If the fatty deposits within the arteries rupture, a blood clot may form and obstruct the blood flow to the heart, causing a heart attack, or to brain tissue, causing a stroke1,2,3,4,5,6. Furthermore, trans fat may damage the inner lining of the blood vessels known as endothelium7. In brief, eating trans fat increases the risk of developing cardiovascular diseases.
  • Diabetes: High intake of trans fat may increase the risk of type 2 diabetes8
  • Weight gain: Diet high in trans fat can cause weight gain and redistribution of fat tissue into the abdomen, even though the total dietary calories are controlled9
  • Inflammation: Studies show that trans fat increases inflammation10,11, which is thought to be the underlying cause of many chronic diseases, including metabolic syndrome, heart disease, diabetes and arthritis. 

Does your cooking oil contain trans fats?

During the process of refining cooking oils, trans fats are generated when the oils are heated at high temperature, leading to trace amount of trans fat in the refined oils. The FDA allows any component of less than 0.5g per serving to be listed as 0g. Hence, bottles of refined oil in the supermarket which proudly claim “Contains 0g of trans fat” may actually contain small amounts of trans fats. Meanwhile, cold pressed oils are devoid of trans fats since no heating or chemical is involved in the production process. Hence, it is better to choose cold pressed oils over refined oils. 

In a nutshell…

The Food and Drug Administration (FDA) has determined that partially hydrogenated vegetable oil is no longer “generally recognized as safe”. Processed food that contains partially hydrogenated vegetable oil is the richest source of trans fat in the modern diet. Hence, keep your intake of trans fat as low as possible by reducing the intake of processed foods. Besides, using cold pressed oils rather than refined oils in your daily cooking will also help minimize your intake of trans fat. 


1. Eur J Clin Nutr.2009 May;63 Suppl 2:S5-21.

2. Eur J Clin Nutr.2009 May;63 Suppl 2:S22-33.

3. Circulation.2007 Apr 10;115(14):1858-65.

4. Am J Epidemiol.1997 May 15;145(10):876-87.

5. Lancet.2001 Mar 10;357(9258):746-51.

6. Am J Epidemiol.2005 Apr 1;161(7):672-9.

7. Am J Clin Nutr.2004 Jun;79(6):969-73.

8. Nutr Rev.2006 Aug;64(8):364-72.

9. Obesity (Silver Spring).2007 Jul;15(7):1675-84.

10. Am J Clin Nutr.2004 Apr;79(4):606-12.

11. J Nutr.2005 Mar;135(3):562-6.