I'm having a bit of trouble understanding what polyphenols are.
According to The American Heritage Science Dictionary (
http://www.thefreedictionary.com/polyphenol ), they contain two or more
benzene rings, but according to Merriam-Webster (
http://aolsvc.merriam-webster.aol.com/dictionary/polyphenol ), they are
polyhydroxy phenols!  Does "poly" refer to the presence of more than one
phenol group, or to more than one hydroxyl group?

Incidentally, according to an article in the United Nations University
Bulletin ( http://www.unu.edu/Unupress/food/V191e/ch02.htm ), vitamin A
reduces the inhibition, at least in the case of iron.

Since the absorption of various divalent cations is mediated by
different mechanisms (mucosal ferritin, metallothionein, calcium-binding
protein...), I wonder whether polyphenols, phytates, and oxalates all
work similarly.

Is there something about thiamine which makes it uniquely susceptible
among vitamins to polyphenol binding?

(I don't have access to journals, but am most eager to find some
publicly accessible internet resources on these subjects.)