I'm not sure if the gut microbiota "improves" in adults at all. It's largely established by the time you're past 3 years old, and even radical dietary changes m

I'm not sure if the gut microbiota "improves" in adults at all. It's largely established by the time you're past 3 years old, and even radical dietary changes mainly just shift the relative abundances around. There's probably still an effect in there, but it seems more likely that it's mainly antibiotics that are killing off gut microbiota variety, with an argument to be made for a role of highly processed foods.