People who have food lodged in their intestines mainly because they don't eat enough fiber and eat processed foods more than anything; You can do this even with an all vegitarian diet. Colon cleansing is merely a process of eating lots of fiber and raw vegitables. I belive overdoing anything can cause health problems, not just with meat. Vegans and vegitarians who don't know how to suppliment their diets can have serious health problems and deficiencies in their systems.