In This Issue

Soy Moves to the Front Line
in the War on Heart Disease

Despite persistent warnings about the need for changes in the average American diet, more than 750,000 people die each year in the United States from coronary heart disease for which moderate to high cholesterol levels are a contributing cause. At least 20 percent of adults have blood cholesterol levels greater than 240 milligrams per deciliter (mg/dL). Another 31 percent fall into the borderline-high category with cholesterol levels over 200 mg/dL.

The U.S. Food and Drug Administration (FDA) estimates that 52 million Americans over the age of 20 are candidates for some type of dietary or drug intervention to lower blood cholesterol. Today, however, it is becoming clear that increased consumption of soy protein offers one of the most promising ways to lower blood cholesterol levels without the use of drugs.

In 1995, a comprehensive review, or meta analysis, of 29 previously published studies, including two from the University of Illinois, confirmed that an average of 47 grams of soy protein per day can produce significant decreases in total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides, without affecting desirable high-density (HDL) cholesterol levels.

John W. Erdman, Jr. (Left), director of the Division of Nutritional Sciences at the U of I, observes as graduate assistant Christine Atkinson prepares a blood serum sample for a cholesterol study on subjects eating soy products. This research has resulted in a proposed rule that would authorize the use of health claims on food labels linking soy protein with reduced risk of heart disease.

"Until that meta analysis took place, few health care professionals noticed that there was a lot of support in the published literature for the idea that soy protein was a dietary factor that could lower cholesterol," says John W. Erdman, Jr., director of the U of I's Division of Nutritional Sciences. "The effect goes beyond the impact of lower fat and cholesterol intake. It is a direct impact of soy protein."

Most recently, Erdman has collaborated on a major new study measuring the long-term effects of soy protein on cholesterol levels in post-menopausal women. Other researchers in the study were from the Division of Nutritional Sciences, the Department of Food Science and Human Nutrition, and the Department of Veterinary Pathobiology at the University of Illinois at Urbana-Champaign and the Division of Epidemiology and Biostatistics at the University of Illinois at Chicago.

In this research, post-menopausal women who had slightly high cholesterol levels received a milk-based supplement with 40 grams of soy protein a day or one of two soy supplements in the form of isolated soy protein. They received this diet for six months and were measured for total cholesterol and for LDL and HDL levels. Primary funding for the study came from the Illinois Soybean Checkoff Board, with additional support from Protein Technologies International, a division of Dupont.

"The bottom line from the study was that LDL—the bad cholesterol—went down, while HDL cholesterol—the good stuff—went up in both the soy groups in the study," Erdman says.

He emphasizes that these findings are especially important because few studies have evaluated women specifically, and post-menopausal women have never been distinguished from women in general, even though heart disease is a leading cause of death in older women.

"Not only were the changes statistically significant, they were maintained over the whole six-month period," Erdman says. "What makes that even more important is the fact that this was the longest study that's every been published on soy."

In another study funded by the Illinois Council on Food and Agricultural Research (C-FAR), Erdman and other researchers have been examining the impact of the level of soy protein consumption on cholesterol lowering. This study focused on men with mildly high cholesterol levels. They were fed diets with 20, 30, 40 or 50 grams of soy protein a day for six weeks.

"Initial evaluation of the results suggests that as little as 20 grams of soy protein—which you certainly can get in one or two servings of soy foods—could reduce cholesterol in this group,' Erdman says. "If this data is confirmed, we will be able to show that just a moderate alteration in the diet can result in a significant reduction in serum cholesterol."

The results of this study will be especially relevant because the Food and Drug Administration has proposed a new rule that would authorize the use of health claims on food labels linking soy protein with reduced risk of heart disease. The agency has tentatively concluded from the scientific evidence that 25 grams of soy protein included in a daily diet that is low in saturated fat and cholesterol may reduce the risk.

"Acceptance of this food labeling rule would be recognition that soy protein is, in fact, important in lowering cholesterol," Erdman says. "It also could be a big boon to soybean farmers as more and more companies would have the incentive to incorporate soy at higher levels in their food products."

If finalized, this new rule would allow for labeling on food products that contain at least 6.25 grams of soy protein in a single serving. Four servings a day would make up the recommended daily minimum intake of 25 grams. Most of the traditional soy foods, such as tofu, would meet the labeling requirements.

Erdman also expects that FDA approval would have a major impact on the soybean industry by spurring commercial manufacturers to develop many new soy food products.

"What's so exciting to me personally is that much of the research on which that proposed rule is based was conducted at the U of I," Erdman says. "This is the culmination of an effort that has been going on since the 1980s. The soybean farmers through the Checkoff Board have had faith in us and supported this work all along. It's taken some years, but we now can see a real outcome from all that support."

The NSRL Bulletin is published three times a year by the National Soybean Research Laboratory at the University of Illinois, 170 Environmental and Agricultural Sciences Building, 1101 W. Peabody Drive, Urbana, IL 61801; telephone (217)244-1706; e-mail nsrl@uiuc.edu; FAX (217)244-1707. Steven T. Sonka, director; Robert J. Wynstra, editor; David Riecks, photographer; Lynn Hawkinson Smith, graphic designer.

Unless otherwise stated, articles may be reproduced or quoted if credit is given to the NSRL Bulletin. The National Soybean Research Laboratory at the University of Illinois is an affirmative action and equal opportunity institution.