Oh, I am not dismissing the microbiome research. As evidenced by the comments in this thread, it seems that it is even taught in nursing/med schools. I think the parent just described the type of person who brings it up to doctors, not that this specific technique should be dismissed.

But I would dismiss any non-conventional medical theory from non-educated (in medical field) people, even if it proves to be correct in the future. When the research and appropriate studies are done (and they prove the initial hypothesis), I will gladly switch my opinion.