> when people consume carbohydrates as the bulk of their diet for length of time the gut microflora changes to species that prefer those This is fairly well su

> when people consume carbohydrates as the bulk of their diet for length of time the gut microflora changes to species that prefer those This is fairly well supported by studies, it even affects oral health. Although the idea of "good" vs "bad" bacteria is more to do with displacing bacteria that processes food into undesirable compounds with something more inert, e.g in the mouth the bacteria that causes tooth decay processes sugar into acid, but in some people this is naturally displaced by another bacteria that when dominant will produce a compound that kills the acid producing bacteria while producing no acid or enamel eroding compounds itself - maybe the natural dominance of that bacteria is affected by absence of excessive sugar intake over ones lifetime, or maybe it's just luck, or a bit of both... but much like gut bacteria, to actively change the dominant bacteria seems to either require a persistent and gradual change in diet, or a shorter and much harsher measure to eliminate the existing population.