Does vinegar increase the iron we can digest from Spinach?
You know, I have always liked to eat spinach with vinegar.  Just steamed and with a splash of plain white vinegar.  It is a very common way to eat spinach around here.

Anyway, I suppose it could have some affect on iron absorption.  Large amounts of vitamin C can increase non-heme iron absorption by as much as 200%.  This article, http://pubs.acs.org/doi/abs/10.1021/jf0203040, seems to indicate that acetic acid, the main component in vinegar, may also increase iron absorption.