However, the polyunsaturated fats in corn and safflower oils have a shorten shelf life, so manufacturers add hydrogen to them to form partially hydrogenated fats. This prolongs their shelf life and also converts the liquid oils to a solid form at room temperature, so they can be sold as stick margarines. The process of converting polyunsaturated fats to partially hydrogenated fats causes them to change to a new shape called trans fats that raises blood cholesterol levels as much as saturated fats do and can increase your chances of suffering a heart attack. Eating too much fat makes you fat and can raise your cholesterol. Margarine is the leading source of fat in the American diet.
Some people still think that eating extra margarine helps to prevent heart attacks.
I'm Dr. Gabe Mirkin on Fitness. A Tavani, E Negri, B Davanzo, C Lavecchia. Margarine intake and risk of nonfatal acute myocardial infarction in Italian women. A Ascherio, CH Hennekens, JE Buring, C Master, MJ Stampfer, WC Willett. Trans-Fatty Acids Intake and Risk of Myocardial Infarction.