My own experience differs with your statement that probiotic aid the digestive system. I have taken boxcar loads of them ranging from OTC to BioK to fancy stuff
imported by my MD from Europe....net result...zip nada.
How do I quantify this. Well, first off, zero weight gain. I have been a good ten
pounds underweight all my life and probiotics did nothing for me. I even took the famed Jordan Rubins stuff for a good few months...again zip.
Even with enteric coated probiotics, prebiotics and every other variation I could find....no effect. Now either I have an alien in my gut........or the stuff is simply
destroyed by stomach acid.
Clinical proof........how about no change in serum amino acids after a couple of years of playing with probiotics.