Why is one not supposed to use soap when washing cast iron?

"Brian Trosko" > wrote in message
...
> levelwave > wrote:
>
> > High amounts of iron have been found in the brains of people afflicted
> > with Parkinson's disease, and it could disrupt the central nervous
> > system enough to aggravate, if not cause, mental disorders.
>
> Correlation is not causation.
>