Parameters of absorption, biotransformation, tissue distribution and excretion have been amply examined in animals and humans. Although much is in fact known, there are still many misunderstandings regarding the differences between animals and men: e.g., data from rodents cannot easily be extrapolated to humans, among other reasons because as rodents reach much higher serum levels of free and unconjugated isoflavones, and because rodents very efficiently transform isoflavones into S-equol. Such differences must be born in mind when assessing the benefits and potential risks of isoflavone exposure.