The intestinal barrier is one of the most important gates between the inside and the outside of the body. It has to let nutrients in and and keep microbes and toxins out. Sometimes the junctions between cells can become too open, making the gut more permeable than it should be, and making the body more vulnerable to foreign substances. Excessive permeability has been associated with a variety of food intolerances and several autoimmune conditions. Some researchers believe that this increased permeability is in fact the cause of many modern diseases. Not only can some plants exacerbate intestinal permeability, but some plant metabolites that are benign when passing through the gut are problematic if allowed to pass through into the bloodstream. This may be the reason that many people are finding relief from chronic diseases when they stop eating all or most plant products.