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3-Food: U.S. study shows non-equivalence of RR-soybeans

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TITLE:  Alterations in Clinically Important Phytoestrogens in
        Genetically Modified, Herbicide-Tolerant Soybeans
SOURCE: Journal of Medicinal Food, Vol 1., no. 4
DATE:   June 1999, in press

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Alterations in Clinically Important Phytoestrogens in Genetically
Modified, Herbicide-Tolerant Soybeans

(Copyright © Journal of Medicinal Food, (Vol 1., no. 4) in
press, Maryanne Liebert Publishers)

Marc A. Lappé, Ph.D., Center for Ethics and Toxics, Gualala CA E.
Britt Bailey, M.A., Center for Ethics and Toxics, Gualala, CA
Chandra Childress, M.S., Children s Hospital Medical Center,
Cincinnati, OH Kenneth D.R. Setchell, Ph.D., Children s Hospital
Medical Center, Cincinnati, OH

The growing clinical interest and use of soybean-based food
products or extracts to increase dietary phytoestrogen intake
makes the precise composition of the key biologically active
ingredients of soybeans, notably genistin and daidzin of
substantial medical interest. Conventional soybeans are
increasingly being replaced by genetically modified varieties. We
analyzed the phytoestrogen concentrations in two varieties of
genetically modified herbicide tolerant soybeans and their
isogenic conventional counterparts grown under similar
conditions. An overall reduction in phytoestrogen levels of 12-14
percent was observed in the genetically altered soybean strains.
Most of this reduction was attributable to reductions in genistin
and to a lesser extent daidzin levels, which were significantly
lower in modified compared to conventional soybeans in both
strains. Significant sample to sample variability in these two
phytoestrogens, but not glycitin, was evident in different
batches of genetically altered soybeans. Given the high
biological potency of isoflavones and their metabolic conversion
products, these data suggest genetically modified soybeans may be
less potent sources of clinically relevant phytoestrogens than
their conventional precursors. These observations, if confirmed
in other soybean varieties, heighten the importance of
establishing baselines of expected isoflavone levels in
transgenic and conventional soy products to ensure uniformity of
clinical results. Disclosure of the origins and isoflavone
composition of soy food products would be a valuable adjunct to
clinical decision-making. 

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