Looking at soybeans to fight cholesterol

High blood cholesterol levels could be lowered by increasing soybean consumption, say researchers at the University of Guelph and the University of Toronto.

The research is timely. The U.S. Food and Drug administration (FDA) has now made it official that soy protein can help reduce the risk of heart disease, one of the leading causes of death in North America. In the fall of 1999, the FDA authorized the health claim that “25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.”

A recent clinical trial involving both the University of Guelph and the nutrition department at the University of Toronto is investigating blood cholesterol levels in participants receiving soy-based food products such as soy burgers, puddings, milk and desserts.

“In addition to soy protein, we’re hoping to find that the isoflavones in soybeans have a positive effect on cholesterol levels,” says Chung-Ja Jackson, a researcher at the Guelph Centre for Functional Foods. He is collaborating with U of T nutrition researcher David Jenkins.

“If they do, we may be able to make dietary recommendations for people who e trying to lower their cholesterol levels and improve their quality of life.”

Some of the group’s findings were presented at the Canadian Federation of Biological Societies meeting in Winnipeg in June 1999 and at the Third international Symposium on the Role of Soy in Preventing and Treating Chronic Diseases, held in Washington, D.C., last November.

Many health benefits
The potential ability of isoflavones to reduce blood cholesterol is a new addition to the growing list of health benefits provided by this group of compounds. Soy foods have already been shown to help prevent other health problems, such as cancer of the colon, breast and prostate, as well as menopausal symptoms and osteoporosis.

Soybeans have been an important part of Asian diets for centuries and are known to help reduce incidence rates of women’s health problems in particular. This is because isoflavones are weak phytoestrogens – compounds that can mimic human estrogen.

Although there are other lifestyle factors that play a role in the decreased rates of women’s health problems in Asia, diets high in soybean products are believed to be a significant factor.

Isoflavones are key
Jackson’s role is to measure levels of isoflavones in soy foods consumed by volunteers, as well as levels of isoflavone metabolic breakdown products in the participant’s urine.

There are 12 different types (isomers) of isoflavones in soybeans and soy food products that she is able to isolate, identify and quantify. Changes in blood cholesterol levels are measured at the University of Toronto.

Jackson’s previous research shows that some soybean varieties have different levels of isoflavones. The location and the year in which the soybeans are grown can also affect isoflavone levels.

The research, together with the development of analytical methods for detecting isoflavones in soybeans and soy foods and their metabolites in urine, was funded by the Ontario Soybean Growers’ Marketing Board and the Ontario Ministry of agriculture, Food and Rural Affairs. The work is being done in collaboration with industrial partners Loblaws, Yves Veggie Cuisine, So Good, Soy City Foods and La Soyaine.