Here are my thoughts, keep in mind they are coming from a raw foodist, so they are going to be swayed in that direction. Much of the food people eat on a regular basis does not digest fully and continues to reisde in their colons and intestines long after it was eaten(think colonics and how many people are finding years old junk). In addition to that, the by-products of cooked food, burning being a chemical change(nearly all food heated above 120 is considered burning), are also left to wreak havoc on not only the digestive system but the entire body. Basically, the average human being is being bombarded at almost all times from many angles with toxic material-pollution, awful food, radiation...etc. The body, no matter how healthy you are, is in a constant state of detoxification-this is one of it's many functions-getting rid of junk it doesn't need, whether through sneezing, coughing, sweating(this is a big one, people are sweating buckets these days) going to the bathroom, or any number of other things. Sadly, more is always coming in than is going out. All that needs to be done is the reverse of that statement. More needs to go out than come in. Cleansing is just a way of giving the body some time to clean house. I don't ascribe to any cleansing products, rather I eat food that has not been altered and I do not mix food all that much so I don't have any digestive reactions-which also leave undigested food to rot inside of you. Interestingly, when I am 100% raw, which I haven't been lately-I've been around 90%, I never have to wear deodorant because I never smell, and almost never sweat.