The most crucial question of them all

[Pamcake]

Bring your trusty bottle of mineral oil
Eat weeds & leaves that you already know are safe, like dandelion (which always seems to be abundant LOL), for their fiber content.

Prior posters are correct about drinking lots of water & keep exercising.
Especially if you are eating high-fiber foods like apples & whole wheat.

If you drink raw water, you'll get diarrhea anyway.
If you don't properly clean off or cook your foods due to lack of whatever, you'll get diarrhea that way too... remember everything on the planet is covered in a thin layer of sh!7, it just happens to be "thicker in Cairo than Indy", so contamination might almost be inevitable

You can always try to catch a giardia infection so that you have chronic diarrhea & never worry about it again