There are two issues here.
Firstly, I have never, ever heard of anyone getting any issues with any of the "leaky gut" illnesses after taking colloidal silver. colloidal silver has been used since the 1930's without anyone ever knowing the term "leaky gut". It is far more likely that Crohn's disease and IBS are by-products of the excessive use of Roundup before the harvesting of wheat and barley, affecting susceptible individuals.
The second issue, and the reason why we do not necessarily accept all research at face value, is that a lot of research is funded by various branches of Big Pharma. A student will get funding for a research project and will submit his paper and get appropriate marks for it within his educational setting, but the wider dissemination of the results is dependant on the attitude of the research funding body.
If you come up with a piece of research that unequivocally recommends colloidal silver as a replacement antibiotic, it will never see the light of day. Any research which has any phrase within it that urges caution, advises of potential problems or which points out unlikely but vaguely-possible side-effects will be championed and published widely so as to bring it to the attention of the widest-possible audience.
To see this in action, you only have to consider the Argyria problem. Every single time, without a single exception, if a question about Colloidal Silver is asked on "Quora", the communal idea-place for (supposed) experts to contribute, then there will be an instant flurry of idiots who put "Colloidal Silver" into Google and then report (as if it is an authoritative answer) in thunderous tones, that colloidal silver "is dangerous", "will turn you blue", "has no proven anti-bacterial effect" and similar half-truths and nonsense.
Some of these people are well-intentioned and think that they are very intelligent, but they haven't the slightest in-depth knowledge of the subject and the nuanced issues with which we deal every day on this forum.
To quote a research paper that is negatively-slanted against colloidal silver is always interesting, but we are living in a deeply-corrupt medical environment which will always champion the chemical over the natural, the expensive over the cheap, the dumbed-down mainstream over the insightful alternative and the corrupt over the honest.
I will say this out loud; WE KNOW COLLOIDAL SILVER WORKS, AND HAS FEWER SIDE-EFFECTS THAN ANY MAINSTREAM ANTIBIOTIC.