Excess estrogenic substances in rodent diets may influence growth, diseases, tumor rates, reproductive performance, and the results of comparative estrogenic and carcinogenesis studies. A standard method for conducting the mouse bioassay for the detection of estrogenic activity in rodent diets was published. We have shown that rodent diets differ significantly in estrogenic activity. In addition, we have reported that some rodent diets contain high concentrations of the phytoestrogens daidzein and genistein equivalent to 4.3 ppb of DES activity and that these phytoestrogens may alter the results of comparative estrogenic and carcinogenicity studies. We concluded that an open formula standardized diet ideally free of estrogenic substances, is essential when performing comparative estrogenic or carcinogenicity studies. We have shown that natural ingredient diets can be formulated to contain less than detectable levels of the phytoestrogens daidzein and genistein by omitting the soybean and alfalfa meals. - phytoestrogens, plant hormones, isoflavones, genistein, daidzein, ligans
| Thigpen, Julius E; Setchell, Kenneth D R; Padilla-Banks, Elizabeth et al. (2007) Variations in phytoestrogen content between different mill dates of the same diet produces significant differences in the time of vaginal opening in CD-1 mice and F344 rats but not in CD Sprague-Dawley rats. Environ Health Perspect 115:1717-26 |
| Thigpen, Julius E; Haseman, Joseph K; Saunders, Hannah et al. (2002) Dietary factors affecting uterine weights of immature CD-1 mice used in uterotrophic bioassays. Cancer Detect Prev 26:381-93 |
