Leaky gut is a condition of the digestive system in which bacteria and toxins leak out through the walls of the intestines into the bloodstream. When it is working correctly, the lining of the intestines forms a barrier that allows helpful substances to be absorbed in the bloodstream, while blocking harmful substances.
There are naturally occurring gaps in the wall of the intestines that allow for some intestinal permeability. When these gaps are small, they are called tight junctions and form a barrier that only allows certain substances to pass through. However, when the gut lining in unhealthy, those gaps can become larger, allowing space for unwanted things like partially digested food particles, certain proteins, and toxins to enter the bloodstream. This is called increased intestinal permeability. The passage of harmful substances creates a cycle of inflammation and changes to gut bacteria. This cycle is associated with a number of chronic diseases.