breast cancer and soy isoflavones

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http://www.sciencedaily.com/releases/2004/05/040507083422.htm

Soy Processing Influences Estrogen-dependent Breast Cancer Growth In

Mice

URBANA -- Highly purified soy foods and soy supplements marketed in

the United States may stimulate the growth of pre-existing estrogen-

dependent breast tumors, according to a study done at the University

of Illinois at Urbana-Champaign.

What's Related

Isoflavone Genistein May Negate Effect Of Common Breast Cancer Drug

Estrogen Found In Soy Stimulates Human Breast-Cancer Cells In Mice

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Related sections: Health & Medicine

Plants & Animals

" Soy has been correlated with low rates of breast cancer in Asian

populations, but soy foods in Asia are made from minimally processed

soybeans or defatted, toasted soy flour, which is quite different

from soy products consumed in the U.S., " said G. Helferich,

a professor of food science and human nutrition, in a study

presented online May 6 in advance of regular publication by the

journal Carcinogenesis.

" Isoflavone-containing products consumed in the U.S. may have lost

many of the biologically active components in soy, and these

partially purified isoflavone-containing products may not have the

same health benefits as whole soy foods, " he said.

Soy isoflavone products are marketed as dietary estrogens to women

over age 50 as a natural alternative to hormone replacement therapy

(HRT), but this is the age group in which most breast cancers occur.

Seventy-five percent of breast cancer cases are diagnosed in women

over 50, and the majority of these cases are estrogen-dependent. For

these women, Helferich said, consumption of highly processed

isoflavone products may pose a risk.

Helferich used an animal model that has been used extensively to

evaluate breast cancer therapies such as tamoxifen. " The results of

this preclinical investigation are especially relevant to

postmenopausal women with estrogen-responsive breast cancers who are

looking for alternatives to HRT, " he said.

In the study, mice were fed equal concentrations of the soy

isoflavone genistein, allowing Helferich to determine the influences

that various bioactive soy compounds had on genistein's ability to

stimulate estrogen-dependent breast tumor growth. " As bioactive

compounds were removed, we observed an increase in estrogen-

dependent tumor growth, " he said.

If genistein had been the only biologically active compound, all

diets would have resulted in similar tumor growth, but that was not

the case, he said.

A soy flour and mixed isoflavones diet and a mixed isoflavone diet

each contained equal amounts of genistein, but differed in the

amount of other bioactive components originally present in the soy

flour. Tumors neither grew nor regressed in animals fed these

diets. " The minimally processed soy flour used in these diets is

more like the soy foods in the Asian diet, " Helferich said.

" Dietary soy products that contained isoflavones in more purified

forms were associated with greater tumor growth. These products are

similar to the materials used in isoflavone-containing dietary

supplements, which is how many Americans consume these compounds, "

he added.

Other researchers contributing to the study were Clinton D. Allred,

F. Allred, Young H. Ju, S. Goeppinger, and R.

Doerge.

The study was funded by grants from the National Institutes of

Health and USDA.

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This story has been adapted from a news release issued by University

Of Illinois At Urbana-Champaign.