That's the thing....if you fast to "completion" they won't. And this is also why I say "relatively comfortable." If you must break it, then do so on juice and stay on juice until you notice the symptoms drop. Then add in raw foods and eventually steamed.
You'll still continue to detox on juice but it will ease things up a bit because you're giving your body energy without much, if any digestion at all.
Most people won't be able to fast to completion for a variety of reasons, but when you fast to completion you've basically detoxed everything that needs to come out. When this happens, you're symptoms disappear. You're only having symptoms because you're going through a cleansing cycle.