Alterations in Clinically Important Phytoestrogens in Genetically Modified, Herbicide-Tolerant Soybeans
(Copyright © Journal of Medicinal Food, (Vol 1., no. 4), 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
Abstract
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.
CETOS Responds to the American
Soybean Association and the St. Louis Post-Dispatch
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