Of course it is not literally sin in your bowels. When you get angry, do you ever see or get the feeling that it starts from deep down inside and comes up and out of the mouth. Next time you get upset, pay attention to see if you can see what I am talking about.
I don't disagree that the Blood of Christ washes us and this is the only way of the removal of SIN.
We also know that what we eat has effect of our spiritual life. Paul gives great council on this, reminds us not to defile our bodies(temples) as they are the temples of God. We also know through modern Science that what we eat affects our ability to think and act. Christ Himself reminds us that through prayer and fasting is the only way to get rid of some demons. Just thought I should clarify that.