I have read about this but never experienced it. Seems the amenorrhea has more to do with body mass/underweight than specifically the "raw diet.." I know many raw foodists who are not especially underweight. If you are choosing a raw diet, it's very important to watch out for those things. Being severely underweight to the point that it causes amenorrhea is not healthy, regardless of your diet.
I certainly do not believe menses are toxic.