Trans fats are edible fats that are chemically altered to remain solid at room temperature. They do not exist in nature and are also known as partially hydrogenated fats. This manufacturing process makes them more stable than natural fats, better for higher frying temperatures and longer shelf lives. They're found in many processed and commercially baked foods, such as doughnuts, cakes, crackers, cookies, and other baked goods.
Trans fats are used for deep-frying in restaurants because they are inexpensive and are comparable in performance to more costly unhydrogenated oils. Margarines and shortenings for home use are also made with trans fats to keep them solid at room temperature.
Unfortunately, partially hydrogenated trans fats are very "heart unfriendly." They can raise LDLs (bad cholesterol) and lower HDLs (good cholesterol) and increase inflammation in blood vessels which makes plaque stickier and damages the cardiovascular system. New York City officials have recently banned trans fats in the city's restaurants.
Sources:
"Revealing Trans Fats." FDA Consumer Magazine. Sept.-Oct. 2003. Food and Drug Administration. 14 Aug 2007.
Alberto Ascherio, Meir J. Stampfer, and Walter C. Willett, "Trans Fatty Acids and Coronary Heart Disease." Harvard School of Public Health. 2006. Harvard School of Public Health; The Channing Laboratory, Department of Medicine, Brigham and Women's Hospital. 14 Aug 2007.
