">how are you going to explain that drastic change to your gut organismss/inhabitants<"
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As you know, we have a symbiotic relationship, but change is life's constant (development, birth, development, death, disintegration, development, etc).  Adaptation works best when change is slow and/or follows a systematic process that is successful.
I believe my 10-year program for dietary change (I'm in the middle of it) will allow my symbiotic friends to adapt too.
Not drastic.