[volkl48]

I mean, there's a well-documented link between colon cancer and inadequate fiber intake.

And it's also well-documented that the average Western diet is highly deficient in fiber and that this is a thing which has gotten much worse in the last 75 years.

There also seems to be at least some light evidence that there may be generational effects - that the starting point of your gut is already bad if your mother's was.