- CHAMPAIGN, Ill. - The
increasingly
consumed isoflavone genistein - a plant estrogen linked to the health
benefits
of soy has been shown in a series of University of Illinois studies to
stimulate the growth of estrogen-dependent human breast-cancer cells
implanted
into laboratory mice.
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- The findings of three studies, funded by the National
Institutes of Health, are detailed in the Journal of Nutrition (November),
Carcinogenesis (October) and Cancer Research (July).
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- The results demonstrate that genistein in various forms
stimulates tumor growth. They also suggest that women with
estrogen-dependent
breast cancer or a predisposition to it may want to reduce their
consumption
of soy products with a high isoflavone content, said William G. Helferich,
a UI professor of food science and human nutrition. Many soy
isoflavone-containing
products are marketed to women over age 50 for the relief of menopausal
symptoms.
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- "Our pre-clinical laboratory animal data suggest
that caution is warranted regarding the use of soy supplements high in
isoflavones for women with breast cancer, particularly if they are
menopausal,"
said Helferich, who was the principal researcher on the papers.
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- For most people, soy is a healthy food and can be used
as part of a healthy diet, he said. Isolated soy protein had been found
in previous UI studies to effectively lower cholesterol. Studies elsewhere
have shown potential relief of menopausal symptoms and protection against
cancer.
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- In the Journal of Nutrition, Helferich and colleagues
show that the estrogen-dependent tumors implanted into experimental mice
models grow at a rate in proportion to the levels of genistein consumed.
Researchers used athymic mice that lack the ability to reject human cancer
cells. After inserting breast cancer cells, researchers were able to
closely
monitor the dietary estrogen to stimulate tumor growth.
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- Genistein at or above 250 parts per million, a dosage
that produces blood levels similar to what is observed in women consuming
soy diets, was enough to stimulate tumor growth.
-
- In the paper in Carcinogenesis, the researchers compared
the isoflavone in its two forms, as a glycoside (genistin, as it appears
in plants) and aglucone (genistein). They found that both forms produced
similar tumor growth rates, and that the conversion of genistin to
genistein
in the body begins with contact with saliva in the mouth.
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- In Cancer Research, Helferich compared soy protein
isolates
containing varying levels of isoflavones. The researchers found that
estrogen-dependent
tumor growth increased as the isoflavone content increased in the
soy-containing
diet.
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- Note: This story has been adapted from a news
release
issued by University Of Illinois At Urbana-Champaign for journalists and
other members of the public. If you wish to quote from any part of this
story, please credit University Of Illinois At Urbana-Champaign as the
original source.
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in any citation.
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