BOSTON — Hardened vegetable oil, a main ingredient of margarine and shortening, raises cholesterol levels and may be even worse for people's health than saturated fat, a study concludes.
The study, conducted in the Netherlands, raises health questions about fatty acids, the kind of fat that makes margarine and shortening hard so they can be used for baking, frying and spreading and not turn rancid.
About a quarter of the fat in a typical stick of margarine is fatty acid. This fat can occur naturally, but most is made when food companies add hydrogen to polyunsaturated and monounsaturated vegetable oils. Food labels list these as hydrogenated oils.
Because these fats make up only 2% to 4% of a typical diet, however, they probably have a relatively small impact on most people's cholesterol levels.
Saturated fat is considered to be the primary villain in the war on cholesterol. This fat, found in meat, dairy products, tropical oils and some other foods, raises cholesterol levels in the bloodstream.
Polyunsaturated and monounsaturated fats were thought to have no effect on cholesterol levels. But the new research suggests that hardening these fats makes them act more like saturated fat.
The study was conducted by Drs. Ronald P. Mensink and Martijn B. Katan of the Agricultural University in Wageningen. It was published in today's New England Journal of Medicine.