The Real Cause of SIBO — Why Everything You’ve Been Told Is Incomplete — The Death Spiral: What SIBO Does Over Time

Once SIBO establishes, the bacteria systematically dismantle remaining defenses. Bile acid deconjugation removes the antimicrobial bile bolus, produces toxic deconjugated acids that damage the enterocyte surface, drives osmotic diarrhea, and depletes fat-soluble vitamins as described. Villous blunting and brush-border enzyme loss develop from ongoing bacterial toxin exposure and deconjugated bile acid damage. Lactase, sucrase-isomaltase, and other disaccharidases are lost. New food intolerances emerge &#8212; not because of new immune sensitivities but because the enzymatic machinery for digestion is being destroyed. Fermentation gas &#8212; hydrogen, methane, hydrogen sulfide &#8212; creates luminal distension that mechanically impairs MMC propagation. The gut slows further. More substrate is available for fermentation. The cycle accelerates. LPS from gram-negative bacteria engages TLR4, generating TNF-&#945; that suppresses MMC activity via the dorsal vagal complex and drives hepatic inflammation &#8212; contributing to metabolic dysfunction-associated steatotic liver disease in a significant subset of long-standing SIBO patients. Vitamin B12 depletion follows as bacteria consume cobalamin and compete with host absorption at the ileal receptor. B12 deficiency worsens ENS function, deepening the motility defect. PPAR-&#947; downregulation from TNF-&#945; exposure breaks the bu