I have been on the
Master Cleanse for 6 days now, and plan on dong it for at least 10 days. This is my second time. I ate a fairly clean diet before beginning. Once you get through the initial cravings and start seeing results, it's really not bad at all. Since starting this cleanse I have lost 8 lbs (half of which I will probably put back on once resuming a whole food diet) I have stopped taking naps in the afternoon, and my usual tension headaches have disappeared. I feel much lighter and have plenty of energy as well.
The only thing I do differently is have a scoop of whey protein mixed with water after I lift weights to prevent muscle catabolism. I do this every other day. It does not seem to affect the cleanse, and I don't feel weaker or suffer prolonged recovery time. Plus my bodyfat percentage on the scale is dropping as well.
I'm sure there are just as many health professionals who recommend this type of thing as oppose it. It just depends on who you happen to be talking to. Do your due diligence and research the different methods out there and find what you are comfortable with.
While I do not subscribe to the idea that I am "detoxifying" I do believe the cleanse affords your digestive tract a break from solid food digestion and allows it to repair and rebuild itself if necessary. As for the mucus lining, your body is continuously shedding and replenishing this regardless of the diet you are following. You can not completely "shed" this like a snake skin, unless you do something invasive like a high colonic enema.
It certainly isn't for everyone as it takes an ongoing commitment, but I do believe a cleanse of this sort is healthy and beneficial. And as with anything else in life - everything in moderation.
Best of luck!