IRO stands for Internal Rinse Out. This is a discreet way of saying enema since a large number of people are quite afraid of the term, and even more afraid of the actual procedure. It's an important part of detoxing and being healthy.
What would happen if you didn't use a trash bag in your trash bin? If you just threw garbage into it and then dumped the bin out? And then, if you never washed the trash bin?
Well, that's exactly what your intestines are like. A trash bin without a trash bag, that has never been washed. Imagine what that trash bin would look like after twenty or thirty years and you begin to get the picture about your intestines.
We were made to eat a lot more fiber, a diet of mostly leafy greens, with running, leaping and walking being activities we did constantly. We were not designed to loaf around breathing in jet fuel (which we're all doing all the time), and car exhaust, and stagnant indoor air. We were not designed to eat frankin'-food made in laboratories, or to be sedentary for 70% or more of the day.
And even if you are very active and eat a fully raw diet, you still will not have perfectly clean insides because our water and air is contaminated. Hence, if you want to get the crap out of you, you need a more direct source of water than drinking it orally.