And if your gut isn?t functioning right, it sets the stage for illness and disease. The gut?the gastrointestinal system?is designed to absorb nutrients that support our bodies and help us make energy, and get rid of things that we don?t need or are toxic. But what happens when the system breaks down? Leaky gut syndrome (LGS) occurs when the lining of the small intestine is damaged, allowing foreign compounds to escape into your bloodstream, which weakens your immune system and triggers autoimmune reactions.