It's easy to do your own research. Pop a bunch of Vicodin, about the amount you'd take after, say, surgery. (Percocet will do in a pinch; DO NOT use heroin for this experiment.) Once your fecal matter has hardened to the consistency of a masonry block, go poop regular style. After straining for about 20 minutes in an ill-fated attempt to pass your feces brick, if an aneurysm hasn't killed you[0], give up and go get a little stool. Place feet upon stool, ass upon toilet seat. Post your results.

(My results: with a little grunting, feces boulder slides out like a greased pig.)

[0] https://www.cbsnews.com/pictures/brain-bleed-8-things-that-t...

[http://www.naturesplatform.com/health_benefits.html]

You can go through this book that references several research papers.