Colon cleanser

Colon cleansing. I've never done it, and I don't think I'll try anytime soon. The idea sounds inviting though. Colon cleansing, others say, is like detox to the large intestine. A good colon cleanser flushes out the excess undigested food stuck in the colon. I wonder if it's effective? I should have asked my doctor when I had my (overdue) annual check-up recently. Maybe next time.