Well, I'm no expert, though I've done some research for myself.

There are a couple ways to clean out the lower intestine. You'd want to clean it because of toxic build up that prevents the lower intestine from functioning well. So in my case, I started to cleanse by fasting and doing enemas, but the enemas didn't really feel that good and after the fast, I still didn't have much correlation between eating and pooping.

The general wisdom is that each time you eat a meal, your bowels should move. That's the best case scenario, but even once a day, regularly, is great. I had a lot of trouble getting stuff out, and I felt plugged up, like there was old stuff gunking up my system.

Colonics versus other treatments: I've never had a natural laxative (like concentrated aloe vera) clean me out the way a colonic does. And an enema doesn't do nearly as much. The colonic's use of pressurized water and massage seems to get in there and loosen things up in a very unique way. There's something about the water's ability to get into the nooks and crannies, combined with the fill and release cycle. The fact that they fill and release many times during a colonic allows for loosening that's really effective if you're gummed and gunked up. The toxic build up is really gluey and sticky and it takes effort to loosen it from the walls of the large intestine. When completed, though, you help tone the lower intestine, and you get all those toxins out. You also get out a lot of the natural organisms in there, which is why you need to make concerted efforts to eat lots of yogurt and/or supplement with other remedies. I choose yogurt.

Would I recommend a colonic for someone with a healthy sounding system? Maybe to check it out. You never know. But I really needed (and still do need) help de-gunking my system. I have a sneaking suspicion I'd be in great shape if I could swear off conventional sugary carbs (pasta, pizza), but I haven't been able to do that yet.