Which is better for your heart-butter or margarine? After years of debate over butter versus margarine, this is a common question asked by many health-conscious consumers. Scientists from the U.S. Department of Agriculture's Agricultural Research Service are working on the answer.

Published in the October 1998 issue of American Journal of Clinical Nutrition, a study by Joseph Judd, Ph.D., and David Baer, Ph.D., compared the effects on blood cholesterol of butter to two types of margarine—a typical margarine containing a moderate amount of trans fat and one containing no trans fat. Twenty-three men and 23 women participated in the study for a total of 15 weeks. Each participant consumed one of the three spreads as their main fat source for a five-week period as part of an average American diet. After a five-week period, the type of spread was changed so all participants consumed each type.

Butter-containing diets raised total and LDL ("bad") cholesterol the most. Compared to the butter diet, both margarine-containing diets had less of an effect on both total and LDL cholesterol. "There is only one conclusion that can be reached," said Dr. Judd. "You limit trans fats in the diet where you can. But don't get overly concerned to the point where you substitute saturated fats for trans fats."