Extension News

Soy - Heart Healthy or Not?


AMES, Iowa --- A recent report from the American Heart Association (AHA) has caused confusion about the benefits of soy protein for heart health. "Many consumers are confused or surprised by the report," said Ruth Litchfield, extension nutrition specialist for Iowa State University (ISU). "ISU has an extensive soy research program so we want to set the record straight."

“The findings are not a surprise,” said Suzanne Hendrich, professor in ISU’s Department of Food Science and Human Nutrition. “The review confirms that soy protein has only a modest effect in lowering LDL-cholesterol, about three percent. It had no effect on HDL-cholesterol or blood pressure.”

Using soy isoflavones alone without soy protein also had no effect on lowering LDL-cholesterol or other lipid risk factors.

ISU experts believe that the Food and Drug Administration (FDA) soy health claim was problematic from the start. Since 1999 the FDA has allowed manufacturers to include the following claim on soy products: “Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease."

“The scientific data do not support the notion that soy protein decreases the risk of heart disease because the studies only examined circulating or blood cholesterol – not heart disease,” said D. Lee Alekel, associate professor in ISU’s Department of Food Science and Human Nutrition. “Linking the health claim to blood cholesterol would have made more sense. Even so, the data show only a modest reduction in blood cholesterol, particularly in individuals who have high levels.”

Alekel said most of the studies reviewed for the AHA report included subjects with lower blood cholesterol levels. “That group is less likely to show a reduction from soy consumption,” Alekel said. “Nevertheless, the conclusion from the AHA report is reasoned and fair.”

ISU experts, however, expressed concern about the AHA report’s discussion of soy ingredients in foods. “The information referencing soy ingredients in foods and extraction methods is incorrect,” said Patricia Murphy, university professor in ISU’s Department of Food Science and Human Nutrition. She said accurate information on soy isoflavones, including metabolism, biological activity, and prevention of chronic diseases such as cancer, heart disease and osteoporosis, is available at the USDA/ISU isoflavone database at http://lpi.oregonstate.edu/infocenter/phytochemicals/soyiso/index.html.

 “Regardless of the recent AHA report and FDA health claim, soy is a good source of high quality protein and can be part of a well-balanced diet,” said Diane Birt, distinguished professor in ISU’s Department of Food Science and Human Nutrition and Director of ISU’s Center for Research on Dietary Botanical Supplements. “This is especially true when soy protein is eaten instead of other sources of protein in a diet that may be high in total fat, saturated fat, and cholesterol.”


Contacts :

D. Lee Alekel, Ph.D.,  Food Science and Human Nutrition, (515) 294-3552, alekel@iastate.edu

Diane Birt, Ph.D., Food Science and Human Nutrition, (515) 294-9873, dbirt@iastate.edu

Suzanne Hendrich, Ph.D., Food Science and Human Nutrition, (515) 294-4272, shendric@iastate.edu

Ruth Litchfield, Ph.D., Food Science and Human Nutrition, (515) 294-9484, litch@iastate.edu

Patricia Murphy, Food Science and Human Nutrition, Ph.D., (515) 294-1970, pmurphy@iastate.edu

Diane Nelson, Continuing Education and Communication Services, (515) 294-3178, dinelson@iastate.edu