> Astrologically speaking, iron ions from spinach are dramatically different than iron ions from a steak, but your biochemistry won't know the difference.

In general, this is not true. In particular, we can read the straight dope ( http://www.straightdope.com/columns/read/696/why-was-spinach... ):

> Spinach's star dimmed once more research was done. It turned out the iron in it couldn't be readily absorbed by the body.