Extension Communications 3614 Administrative Services Building Ames, Iowa 50011-3614 (515) 294-9915

8/27/03

For immediate release

Contacts:
Ruth Litchfield, Ph.D., Food Science and Human Nutrition, (515) 294-9484, litch@iastate.edu
D. Lee Alekel, Ph.D., Food Science and Human Nutrition, (515) 294-3552, alekel@iastate.edu
Manju B. Reddy, Ph.D., Food Science and Human Nutrition, (515) 294-2024, mbreddy@iastate.edu
Darcy Johannsen, MS, RD, Food Science and Human Nutrition, (515) 294-5088, djohanns@iastate.edu
Diane Nelson, Continuing Education and Communication Services, (515) 294-3178, dinelson@iastate.edu

Quest to Understand the Role of Soy in Decreasing Risk of Heart Disease Continues

AMES, Iowa -- As researchers continue to explore how soy foods affect cardiovascular disease risk, consumers are reminded to look beyond individual research reports and consider how all the studies fit together. "The findings of a single study are less important than the summary of a collection of studies," reminds Ruth Litchfield, Iowa State University Extension nutritionist.

For example, a study recently reported in the Journal of the American Medical Association found that a diet high in soy protein, gelatinous fiber, almonds and plant sterols is as effective in managing blood cholesterol as a popular cholesterol-lowering supplement. The diet included foods such as oat bran, barley and okra, in addition to the fiber supplement Metamucil, plant sterol-enriched margarines, beans and olives; plus soy protein in the form of tempeh, tofu and meatless meat patties.

However, researchers at ISU believe that the benefits of the tested diet were more likely due to the fiber and sterols than to the estrogen-like compounds called isoflavones that are associated with soy protein. "We cannot say that soy isoflavones alone affect blood cholesterol," said Lee Alekel, ISU associate professor in nutrition, who has spent 10 years studying the benefits of soy isoflavones on osteoporosis and cardiovascular disease risk.

A summary analysis of 10 studies, including a study at ISU, recently published in the European Journal of Clinical Nutrition found that soy-associated isoflavones did not affect circulating LDL and HDL cholesterol levels significantly. "It appears that the benefit on cardiovascular disease risk is due to the protein and its associated components, rather than the isoflavone in isolation," said Alekel.

Researchers say soy isoflavones may affect other risk factors for cardiovascular disease, particularly the flexibility of the arteries and cells that affect the lining of the arteries. Alekel says, "Another plus is that isoflavones, unlike estrogen, do not have a harmful effect on coagulation factors, which in turn, may increase the risk of cardiovascular disease."

Litchfield points out that while the sum of research studies indicates a link between soy consumption and reduced heart disease risk, the precise soy component is not yet known. "The positive association may be due to a component we haven't yet identified, or to a component that hasn't been studied alone."

Enough evidence does exist, however, for the American Heart Association to recommend daily consumption of at least 25 grams of intact soy protein with its associated phytochemicals to decrease risk of heart disease. "Consuming as much as 25 grams of soy protein through dietary sources is possible, but indeed very difficult for most Americans," Alekel said.

Since 1999 the Food and Drug Administration has allowed food marketers to use the claim "diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease. One serving of (name of food) provides __ grams of soy protein." To qualify for the claim, foods must contain per serving:

* 6.25 grams of soy protein
* less than 3 grams of fat
* less than 1 gram of saturated fat
* less than 20 milligrams of cholesterol
* sodium value of less than 480 milligrams for individual foods, less than 720 milligrams if considered a main dish, and less than 960 milligrams if considered a meal.

"Soy protein products are good substitutes for animal products because they are a 'complete' protein. They contain all the amino acids essential to human nutrition, without excess fat, especially saturated fat. Complete proteins are also found in animal products, such as meat and dairy products, but they typically include saturated fat as well," said Litchfield.

Currently, soy isoflavone research at ISU is focusing on its interaction with bone and oxidative stress. Alekel leads the team investigating interactions with bone, while Manju Reddy heads up the work on oxidative stress related to cardiovascular disease. Researchers are seeking healthy, post-menopausal female participants. Interested individuals are asked to contact Darcy Johannsen at (515) 294-8673, djohanns@iastate.edu.

-30-

OPTIONAL SIDEBAR

For more information, check these Web sites:

Journal of the American Medical Association
http://jama.ama-assn.org/cgi/content/abstract/290/4/502

European Journal of Clinical Nutrition
http://www.nature.com/cgitaf/DynaPage.taf?file=/ejcn/journal/v57/n8/abs/1601628a.html

Food and Drug Administration
http://www.cfsan.fda.gov/~dms/fdsoypr.html

-30-

ml: imajor

News Menu | ISU Extension