What is trans fat?

Most trans fat is formed through an industrial process that adds hydrogen to vegetable oil, which causes the oil to become solid at room temperature.

This partially hydrogenated oil is less likely to spoil, so foods made with it have a longer shelf life. Some restaurants use partially hydrogenated vegetable oil in their deep fryers, because it doesn't have to be changed as often as do other oils.

Some meat and dairy products have a small amount of naturally occurring trans fat. It's not clear whether this naturally occurring trans fat has any benefits or harm.