[existencebox]

"You don't." Now, that's slightly hyperbolic for effect, but let me clarify: We know SO LITTLE about actual correlations between gut microbiome and how it impacts the body in the long term. We can barely even correlate a single given feature of your gut as being related to, say, obesity. (My partner spent some time in a lab asking this precise question; I will, if I can get a source, give some sort of paper link when I get home from work) There's a lot of fad science around diet and microflora nowadays, but the sense I get as an observer of someone who is in that field, it's about as wishy washy as if you asked a computer scientist "what are the leading causes of disk failure." We know that if you shove a screwdriver through it it won't be happy, but there's still tons of debate about the finer points. (And your gut is WAY more complex than a HDD).

So, takeaway from this ramble, do what your body responds well to, and keep to generally "good patterns" of hygene and balanced diet. Anecdotally, and from many practicing physicians, this tends to work out "ok" in the long run.