Trans fats are a type of unsaturated fat that have been chemically altered through a process called hydrogenation, which adds hydrogen atoms to liquid vegetable oils, making them more solid at room temperature.
This process was originally used to improve the shelf life and stability of fats used in commercial food production, leading to their widespread use in products like margarine, baked goods, and fried foods. However, trans fats are now known to be particularly harmful to health, as they raise levels of low-density lipoprotein (LDL) cholesterol while lowering high-density lipoprotein (HDL) cholesterol, significantly increasing the risk of heart disease.
Due to these health risks, many countries have implemented regulations to reduce or eliminate trans fats from the food supply, and home chefs are advised to avoid products containing partially hydrogenated oils.