Study Shows Soy Protein Lowers Men's Cholesterol

Soy protein can be an important ally in lowering cholesterol, according to new findings from a study conducted at the Children's Nutrition Research Center in Houston, Texas. This research, published in the October issue of American Journal of Clinical Nutrition, may also explain why previous studies have produced conflicting evidence concerning the merits of soy protein.

The study results suggested soy protein can enhance the effects of a diet designed to lower cholesterol. This holds true for men whose levels are in the safe cholesterol range and those above it. The Children's Nutrition Research Center is jointly managed by the Agricultural Research Service, the chief research agency of the U.S. Department of Agriculture, and Baylor College of Medicine.

The study involved 26 men, 20 to 50 years of age, half of whom had high cholesterol. All the men went on the National Cholesterol Education Program's Step I diet to lower their cholesterol—but with a special twist. Half of the subjects were getting their protein from soy; half from meat.

Then, after a 10-to-15 week "washout" period, the two groups swapped diets; those receiving their protein from soy switched to meat, and vice versa.

While both groups of men experienced improved blood cholesterol on both diets, those receiving soy improved more than those receiving meat protein, regardless of age or weight.

Low density lipoprotein-cholesterol (LDL-C) is associated with increased heart-disease risk. Men with cholesterol problems who went on the meat-protein diet dropped their LDL- cholesterol 8 percent, but their LDL-cholesterol dropped 13 percent on the soy-protein version. The percentage for men with "safe" LDL-cholesterol levels was smaller—5 percent for meat and 11 percent for soy.

Researchers suggested that previous studies finding little benefit from soy may not have included a "washout period" or adequately monitored subjects' diets. The men in this study ate only pre-packaged meals prepared at the center.

Scientific contact: William W. Wong, USDA-ARS, Children's Nutrition Research Center at Baylor College of Medicine, Houston, Tex., (713) 798-7168; fax: (713) 798-7119, wwong@bcm.tmc.edu.