The point isn’t about one specific chemical, but rather the principal that the prevalence of non-nutritious, edible chemicals seriously augments the dark, warm controlled environments of our guts.
Nutrient capture as a whole, shifts in a way that, at the bottom of the tract, there are chemicals that humans leave unused, but which are still useful to certain opportunistic organisms.
If only those chemicals are available, and normal food is absent, every member of the environment is forced to deal with scarcity, and the strongest survive, and fill the void if they can.
If those organisms are forced to opperate with greater efficiency, then their capacity to deal with adversity offers them an advantage as an invasive species, and they will prevail in general, everywhere, not just in the adverse scenario.