Our data suggest conventionally and organically grown soybeans of the same variety have comparable levels of phytoestrogens. In keeping with our previous studies, we observed subtle differences in phytoestrogen makeup by variety but little betweensample variability. Altering the growing conditions by changing pesticide regimes appeared to have little or no influence on phytoestrogen content. This lack of variability between organic and conventional soybeans suggests that herbicide treatment or nontreatment of genetically similar soybeans does not change the plant's phytoestrogen development. This observation is relevant to our previous study which showed significant phytoestrogen variability between herbicide-sprayed conventional and genetically modified soybeans14. One explanation of these findings, that differing levels of herbicide use between the conventional and genetically modified beans affected the phytoestrogen development differently, is not supported by the present study. Our present findings reinforce the conclusion that the differences reported in Roundup Ready soybeans were likely a result of the genetic modification process and not differential herbicide use.
Our findings may also be relevant to the general consumer of soy-based food products. Our study shows that organic and conventional soybeans have comparable levels of phytoestrogens. We cannot exclude the possibility that other nutritional components in organic and conventional soybeans differ. However, our data suggest consumers who may wish to reduce their ingestion of pesticides by eating organic soybeans will not lose out on phytoestrogens by making such a choice.