This myth is so widespread that some people are obsessed with regularity -- over-relying on laxatives or using risky colonic machines. But your colon is pretty good at fighting bacteria. After all, its job is to get rid of toxins.
Besides, you’re probably more regular than you think. Three or fewer BMs in a week is a sign of constipation. So don't be concerned unless you go less than every other day, have pain, trouble going to the bathroom, or there's a change in how often you go.