Animal meat or dairy products contain very little natural trans fat; If fried repeatedly with natural fat, it will also produce a small amount of trans fat. Trans fats ingested by humans mainly come from partially hydrogenated vegetable oils. Hydrogenation is a food industry technology invented in the early 20th century. It was first used by the edible oil brand "Crisco" in 19 1 1 year. Partial hydrogenation will change the molecular structure of fat (make oil more resistant to high temperature, not easy to deteriorate, and increase the shelf life), but hydrogenation will also turn some fat into trans fat. This kind of fat is widely used in packaged food in the market and fried food in restaurants because it can increase the crisp taste of food and is easy to store for a long time.
Trans fat is classified as unsaturated fat, so it is regarded as a healthier substitute for saturated fat until it is found to be harmful to health, especially because the widely publicized concept of healthy eating encourages the use of trans fat. Therefore, many fast food chain stores have changed from the original oil containing saturated fatty acids to trans fats.
Trans fats are strictly controlled in a few countries, while more countries require food producers to indicate whether their products contain trans fats, and there are also many lawsuits (mainly against fast food restaurants) caused by trans fats. Many food companies have voluntarily stopped using trans fats in their products or increased their product lines without trans fats.