My current theory is that many people have fungus/yeast problem; including and especially me. The fungus forms roots that eventually penetrate the intestinal wall, making it permeable. Those roots act just like sponges that will absorb the larger food molecules and pass them into the bloodstream.
The immune system then reacts to the alien invaders; causing something like detoxification reactions within the body. The detox is good. The feelings are not.
At any rate, something has caused the permeation of the lining. One needs to find that cause.
I've read that aloe vera juice or gel will help heal the tissue of the gut.