Just last night I decided to cutback from 12mg to 3mg for other reasons.
But regarding the effect on lower GI microbiome and symptoms, I was at one time practically disabled with non-ulcerative colitis, but the disorder spontaneously disappeared about 25 years ago and has not re-surfaced while using melatonin.
I have no gut problems. Been having probiotic filled yogurt with fruit for dessert every night for years. Plus, I drink Kombucha every night before dinner instead of wine. Kombucha is the best source of probiotics. I like the Mojita flavor, slightly tart like a real Mohita. What’s not to like?