...and yet sauerkraut, which famously is fermented for preservation, is famously good for your gut?

As someone who ran a farm and regularly had to choose how to best "preserve" excess food, I can tell you it is complicated. There are sugars that kill bacteria in jellies, jams, some canned fruit (not for me), smoking/salting of meat (probably not the best), and pressure canning (sometimes with citric acid to lower pH) which seemed the best. Air-curing of meat/other things w perhaps IR or equal the future? Obviously fermentation good to a point (all these things are trade-offs, a little bad stuff to foil the bugs that can kill you)

Funny that most modern foods (sausages, cured meats, sweets, spirits, cheeses etc) are historic and subsequently popularized attempts at food preservation, while our gut biomes were probably going "ew!"

On the gut side, growing evidence that its...complicated? No such thing as "perfect" gut biome as it depends on one's genetics and environment, plus the ratios? Perhaps fiber & mother's milk, lacto bacillus etc "gut biome helper"? My take:

https://scottvern.medium.com/an-imagined-interview-with-the-gut-brain-bb52d2af3d45

Correct me if I'm wrong...