Mark (Breda, Nl) on 04/13/2016:
Borax turns into boric acid depending on pH. If the pH is low (acid) like in your stomach, borax turns to boric acid, if the pH turns high again (alkaline) like in your intestines, most of it will be borax again.
Boric acid and borax are about equally effective.
I got this info straight from Walter Last, who wrote the article on borax.