Trans fatty acids are produced during the hydrogenation of vegetable oils. Partially hydrogenated vegetable oils can replace naturally solid, saturate-rich fats such as butter, lard and beef tallow, and occur naturally in small amounts in meats and dairy products. Research suggests that trans fatty acids (trans fats) raise total and LDL cholesterol levels, and lower HDL cholesterol, causing the arteries to become more rigid and clogged. A diet high in trans fats could accelerate the development of cardiovascular disease. Partially hydrogenated vegetable oils containing trans fats came into popular use in the 1960s and 1970s as substitutes for animal fats which provide relatively higher dietary cholesterol and levels of saturated fat.
Trans Fatty Acids are the worst fatty acids for your health. Found in most processed foods in the form of partially hydrogenated vegetable oils, trans fats cannot be digested. They remain in your bloodstream, clogging arteries.