He Shou Wu - Prepared vs Unprepared

According to this site, the prepared version of He Shou Wu (herb stewed in black bean sauce) is a health tonic whereas the unprepared version (raw herb) is just a laxative that has little or no tonic properties.

http://www.secrets-of-longevity-in-humans.com/fo-ti-root.html


What exactly does stewing the herb in black bean sauce do to make it a health tonic? And why black bean sauce - what's so special about it? One would normally think that stewing or cooking would destroy the nutrients and other beneficial things in the herb. Could anyone please shed some light on this mystery?

Also, if you bought a 10:1 extract of He Shou Wu, how do you tell if it's the prepared version? Is the color of the extract an accurate indicator? Say, if the color is dark brown, does it mean that it's the prepared version or not necessarily?

Thanks!