The Real Cause of SIBO — Why Everything You’ve Been Told Is Incomplete — The Oxygen Economy and the Host Capacity Model

Now I want to take you somewhere most SIBO researchers have not gone &#8212; into the metabolic interior of the gut lining itself. Because this is where all the upstream causes converge, and this is where my research has been focused for years. In a healthy gut, the epithelial cells lining the small and large intestine consume oxygen in vast quantities to fuel mitochondrial beta-oxidation of butyrate and other short-chain fatty acids. This oxygen consumption is so extensive that it creates a state of physiological hypoxia in the gut lumen &#8212; oxygen levels drop below 1% near the mucosal surface. This is not an accidental side effect. It is a designed feature of the system. It is what makes the gut lumen hostile to the organisms that do not belong there. A 2024 study confirmed that butyrate not only fuels beta-oxidation but also stabilizes hypoxia-inducible factor through noncompetitive inhibition of HIF prolyl hydroxylases. Butyrate is simultaneously the energy source and the regulatory signal that maintains the oxygen gradient. The gut lining is actively preserving its own hostility to the wrong organisms using the metabolic products of the right organisms. When colonocyte metabolism is disrupted &#8212; by any of the upstream causes in this article &#8212; the cell can no longer sustain beta-oxidation. It switches to glycolysis. Glycolysis consumes far less oxygen. The ox