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Isoflavone-enhanced
dietary supplements containing genistein may counteract the
tumor-fighting effects of tamoxifen, the anti-cancer drug
used in women with estrogen-dependent breast cancer, according
to researchers at the University of Illinois at Urbana-Champagne.
Genistein
is an estrogen-like component found in legume plants. It is
often identified as one of several desired isoflavones in
soy products, including soy-enhanced drinks and dietary supplements.
Dietary isoflavones also can be found in both subterranean
and red clover supplements.
In a pre-clinical
study, researchers divided 66 mice into six groups to watch
the effects of estrogen and various amounts of tamoxifen and
genistein. All of the mice had their ovaries removed. Estrogen
and tamoxifen implants were put into the mice, and estrogen-dependent
breast cancer cells were injected.
Before
adding genistein to their diet, the tamoxifen had stopped
tumor growth in the mice. Adding genistein in amounts similar
to levels that people can get by eating isoflavone-rich dietary
supplements resulted in enhanced growth of estrogen-dependent
tumors and increased estrogen-responsive gene markers, according
to the study published in the journal Cancer Research.
"These
results raise concern about consuming dietary isoflavone supplements
in conjunction with tamoxifen in postmenopausal women who
have estrogen-dependent breast cancers," said William
G. Helferich, professor of food science and human nutrition
and head researcher.
"This
study also applies to women who are self-medicating with dietary
estrogenic supplements by showing the supplements could negate
the protective benefit of tamoxifen," added Helferich.
Source:
Breast Cancer
Week of May 12, 2002
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