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No-'stick' tips for heart-healthy diets.

With the addition of hydrogen, unsaturated oils undergo a transformation that straightens out a kink in their natural form. These stiffer "trans" fats permit stick margarine and shortening to remain solid at room temperature, as saturated fats do. But new research with human volunteers now confirms earlier reports that such fats also increase cholesterol concentrations in the blood.

Three years ago, a Dutch team came to the same conclusion (SN: 8/25/90, p. 126). But that group fed a laboratoryconcocted margarine-like product to young, healthy volunteers eating a traditional, high-fat diet.

"We took that a step further," says Alice H. Lichtenstein of the U.S. Department of Agriculture (USDA) Human Nutrition Research Center on Aging at Tufts University in Boston. Americans typically derive 35 percent of their calories from fat; she cut fat in her trials to 30 percent of calories, a level the American Heart Association recommends.

Her team then recruited 14 men and women age 44 to 78 with "borderline high" cholesterol (238 milligrams of cholesterol per deciliter of blood) and charted changes as they switched between a typical U.S. diet and two 32-day diets, all with the same number of calories. The first alternative derived two-thirds of its fat from corn oil, the second from a commercial corn-oil margarine. Both corn-oil-based diets contained proportionately about half the saturated fat of the baseline diet.

Many lipids in the blood fell in both the lower-fat and less-saturated-fat diets, Lichtenstein's team writes in the February ARTERIOSCLEROSIS AND THROMBOSIS. But compared to margarine, liquid corn oil fostered larger drops: 12.7 versus 7.4 percent in total blood cholesterol and 17.4 versus 10.4 percent in "bad;' or low-density-lipoprotein, cholesterol.

These results "are very definitive" in pointing out the advantages of reducing overall fat and switching to products that contain unsaturated fats, says Lichtenstein. An even longer, more involved study by USDA scientists in Beltsville, Md., finds much the same thing, says Joseph T. Judd, who led the still-unpublished trial involving 29 men and an equal number of women.

The USDA groups paper "adds one more block to the argument that trans fatty acids should be reduced in the American diet," says Scott M. Grundy of the Center for Human Nutrition at the University of Texas Southwestern Medical Center in Dallas. However, he says, stick margarine "is still better [for the heart] than butter - by far." And soft margarine - with less trans fat - is better than hard, he adds.

David Kritchevsky of Philadelphia's Wistar Institute also notes as interesting the Boston groups finding that margarine did not raise concentrations of the cholesterol carrier Lp(a) in the blood; it had in the Dutch study This might prove important, he argues, since highLp(a) can slow the natural breakdown of blood clots -- a leading cause of strokes and heart attacks.
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Title Annotation:research indicates reduced trans fatty acids in diet can lower cholesterol levels
Author:Raloff, Janet
Publication:Science News
Article Type:Brief Article
Date:Mar 6, 1993
Words:471
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