NEW YORK -- The U.S. Agriculture Department, in an unpublished study, has found that fat in margarine may contribute to heart disease.
In response to harsh criticism in the past few years about the amount of saturated fat in the American diet, many food manufacturers have reluctantly switched from tropical to partially hydrogenated vegetable oils made from soybean and corn oils.
Now new data show these oils -- found in margarine, vegetable shortening and a host of products ranging from doughnuts to cookies and crackers -- may also be hazardous.
The suspect ingredients are produced when food manufacturers convert vegetable oils to margarine or shortenings that are solid or semisolid at room temperature.
This process creates trans fatty acids. For years, studies about trans fatty acids were conflicting: Evidence showed they both raised and lowered cholesterol levels. But several studies in the past two years have pointed to the harmful effects of these acids.
A study by two Dutch scientists, reported in the New England Journal of Medicine in 1990, was the first to cause widespread concern. It showed that trans fatty acids increase harmful elements in cholesterol and lower protective elements.
The Agriculture Department has now confirmed the Dutch study. While the Agriculture Department study, conducted for the Institute of Shortening and Edible Oils, an industry group, has not yet been published, those who have seen it say it supports the earlier Dutch work.
"Evidence is growing that trans fatty acids raise cholesterol levels just like saturated fatty acids," says Dr. Scott M. Grundy, director of the center for human nutrition at the University of Texas Southwestern Medical Center and an expert on coronary risks of dietary fats, who has seen the study. "We should try to reduce the amount of trans fatty acids in foods."
Researchers say the findings are no excuse for people to revert to butter. "We don't want people going back to saturated fat," says Joseph Judd, the head researcher on the Agriculture Department study.
But the findings do suggest that partially hydrogenated oils, important ingredients in margarine even before the concern over tropical oils, are no nutritional improvement.