If you want science then start with Wikipedias articles:
- https://en.wikipedia.org/wiki/Human_digestive_system
- https://en.wikipedia.org/wiki/Dietary_fiber
- https://en.m.wikipedia.org/wiki/Liquid_diet
And then read all the references when you want to dig deeper.
I have no problem with being taxed 40+% and then don’t have to worry about being ruined by a trip in an ambulance, especially the older I get.