Why Your Oil Became Partially Hydrogenated
Partially hydrogenated vegetable oil, the current villain of the food industry, was once considered a shining achievement for reducing saturated fat intake. "A lot of people have demonized partially hydrogenated soybean oil, but they forget how it came about," says Mark Matlock, senior vice president of research at Archer Daniels Midland. "If you go back 15 or 30 years, french fries were fried in beef fat, and the effort at the time was to remove the saturated fats that it contained." It also helped that partially hydrogenated oil was cheap to produce and lasted considerably longer than regular oil.
Partially hydrogenated oils are created from liquid vegetable oil through a process called hydrogenation, which forces hydrogen into the oil until it reaches the desired consistency and changes its chemical structure. Hydrogenating oils completely makes them too solid to use easily in cooking, but partial hydrogenation can make a margarine that is easy to spread on toast but doesn't go bad quickly as butter does.
But partial hydrogenation also gives the oil molecules an odd shape called the trans configuration (hence the name trans fat), which causes them to act like a saturated fat in that they increase "bad" LDL cholesterol and can clog arteries. Trans fats, which occur naturally in meat and dairy products but at low levels, also lower "good" HDL cholesterol, which even saturated fat doesn't do.
Many of the new margarines that are free of trans fat mix completely hydrogenated oil, which is very solid, with unsaturated oil, a liquid, to achieve a desirable consistency without making the oil form the trans configuration. Experts say that the new oils and margarines should be more healthful. Of course, experts also once thought that about partially hydrogenated oil.