Hi: A lot of people do have clean lower bowels when viewed on colonoscopy where the mucus and other debris comes from with the P&B shakes is the small bowel.The wise use of major colon cleansing is good a few times per year and will not thin the bowel wall.Mucous is constantly produced to protect the membrane.The mucosal layer is what harbours the toxins & pathogens and when this layer is partially removed by p&b it transports to the large bowel for removal; and more mucus is produced to protect the membrane.Over cleansing like overeating will produce long term results no one wants. It took years to built up the debris you can't get rid of it in a day. Do p&b for 1 week then layoff for 6 use p to keep bowels regular or other fibre combinations they are better than Psyllium (for reqular use) which is only one form of fibre (mucilage) )there are cellulose,hemicelluose,lignins,pectins,gums and mucilages.