The man-made fats that have replaced cholesterol-raising saturated fats in margarines, snacks and countless fast foods could be causing 30,000 deaths a year from heart disease, Harvard researchers contend.

The "trans fatty acids" in partially hydrogenated oils are just as risky or more so than the heavy natural fats found in butter, beef tallow, lard and tropical oils, according to the editorial in Monday's issue of the American Journal of Public Health written by Dr. Walter C. Willett, professor of nutrition and epidemiology, and medical school professor Dr. Alberto Ascherio.

Like the saturated fats, trans fatty acids raise levels of low density lipoproteins-often called bad cholesterol, Willett said. But the trans fatty acids also lower the levels of high density lipoproteins-good cholesterol-to deliver a kind of double whammy and give "a greater adverse impact than saturated fats."