The choice between margarine and butter may become easier thanks to a recent study

ATLANTA (CNN) -- Which is the lesser of two evils when putting spread on your bread -- cholesterol-laden butter or margarine containing trans fatty acids? New research shows the best choice may be a specific kind of margarine already found on supermarket shelves.

A study presented this week at the American Heart Association's conference in Dallas found a diet that uses low-trans or trans-free margarine, usually sold in tubs or liquid form, is a heart-healthy butter alternative.

The study, by Dr. Margo Denke of the University of Texas Southwestern Medical Center, tested whether a margarine-based diet rather than a butter-based diet can lower cholesterol as much as medication can. She used only margarines low in trans fatty acids.

"What we have found so far is about 25 percent of the population gets a mean cholesterol lowering of about 25 points," she said.

When study participant Lisa Jackson, 18, switched from butter to margarine, her cholesterol plummeted 109 points.

Studies show switching to low-trans fat margarine can help lower cholesterol levels

"I was surprised," she said. "It was real high to begin with -- higher than Dad's."

Many stick margarines sold in stores are high in trans fatty acids, which form when vegetable oils are hydrogenated into solids.

Trans fat was once thought to be better than butter's saturated fat. But studies have found it may be just as harmful in increasing blood cholesterol.

Dr. Walter Willet of Harvard University said trans fat is worse for the heart than saturated fats, but advised choosing margarine low in trans fat rather than butter.

"Avoiding trans fatty acids will lower the bad form of cholesterol or LDL," he said. "Also, it can raise the good forms of blood cholesterol, so you get several benefits by avoiding trans fatty acids."

A twist in the butter debate is expected to debut next year. Two new margarines that makers say help block cholesterol absorption will hit the U.S. market.

The margarines, Benecol and Unilever's Take Control, contain plant stanol esters, natural substances that have lowered cholesterol in studies.

"Benecol is an additive or supplement to the margarine, and that gives an extra kick to cholesterol-lowering, so you get a double benefit, said Dr. Scott Grundy of the AHA.

Despite improvements in margarine, doctors say the best way to keep cholesterol in check is still to use as little margarine, butter or other fats as possible.

Food & Health Correspondent Linda Ciampa contributed to this report.