Study raises questions about when and how far to lower blood cholesterol in elderly men

SAN ANTONIO, March 2 – For the first time, researchers report that whether a person’s cholesterol levels are high or normal, those who add soy to their diets may see an increase in levels of “good” cholesterol in their blood.

Results of the study are presented today at the American Heart Association’s 41st Annual Conference on Cardiovascular Disease Epidemiology and Prevention.

When 40 grams of soy protein were added to the daily diet of a group of men and women with normal lipid profiles, their levels of “good” high-density lipoprotein (HDL) cholesterol increased, while their levels of “bad” low-density lipoprotein (LDL) cholesterol were not significantly affected,” says Jiang He, M.D., Ph.D., associate professor of epidemiology at Tulane University School of Public Health and Tropical Medicine in New Orleans, and lead author of the report.

Depending on how it is processed, soy protein may take the form of a liquid, flour or a concentrated powder. As textured vegetable protein, it is often used as an extender for meat or poultry products. This clinical trial in China is the latest of scientific studies showing that regular consumption of soy protein has a beneficial effect on cholesterol levels and may lower the risk of heart disease. Previous soy studies have focused on improving lipid profiles in people who have high cholesterol, but the effects of soy supplementation on individuals with normal cholesterol levels have not been well documented.

“People in China usually consume a low-protein diet and get little animal protein. Our study demonstrates that, in a population with normal cholesterol levels and low dietary protein intake, soy protein increases HDL in the bloodstream, but does not significantly alter LDL,” says He.

Researchers studied 60 men and 90 women aged 35-65, all of whom had normal cholesterol levels. Half of the participants ate cookies containing soy protein supplements every day, while a control group consumed a complex carbohydrate placebo instead. After 12 weeks, those receiving soy supplements showed a 4.7 percent increase in HDL compared to the control group.

Although there was a small increase in LDL among soy-consuming participants, it was not considered significant. Among people with high cholesterol, a number of U.S. studies have shown that daily soy protein consumption actually lowers LDL, in addition to raising HDL levels.

Unlike the vegetable protein contained in most grains and legumes, soy protein is “complete,” meaning that it contains all the essential amino acids found in animal protein.

“Most bean proteins are good for health,” He says. “However, soybean protein is the only one that has been documented to affect cholesterol levels by clinical trials conducted in western countries.” Previous clinical trials have demonstrated that adding soy protein to the diet can improve lipid profiles in individuals with abnormally high cholesterol. As a result, the American Heart Association’s Nutrition Committee recently issued a statement supporting wider use of soy products for those with high cholesterol.

“There is increasing evidence that consumption of soy protein in place of animal protein lowers blood cholesterol levels and may provide other cardiovascular benefits,” according to the Nutrition Committee’s statement. The association recommends that consumers with high cholesterol consider eating three or more servings daily of products that provide 10 grams of soy protein per serving to reduce their total and LDL cholesterol levels.

Soy protein can be easily incorporated into many kinds of foods, He says. High-protein beverages, energy bars and other types of soy-containing products are already available in U.S. stores, and others are being introduced on a regular basis.

Co-authors include Paul K. Whelton, M.D., M.Sc.; Dongfeng Gu, M.D.; Xigui Wu, M.D.; and Xiufang Duan, M.D.

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