Dietary Fructooligosaccharides increase Intestinal Permeability in Rats
Okay, so this is a rat study and the amount of FOS given to the rats was excedingly high (4500 GRAMS for an average sized male human–I thought this might be an error, but no corrections have been noted), but this study still illustrates that probiotics and prebiotics given willy-nilly is not always a good thing.
We still have much to learn on this important topic, and much research is focused on identifying what types of probiotics are good for what application (IBS, lower inflammation, immune stimulatory…). It may be years yet before we fully understand all the nuances of pre/probiotic use.