2026 Volume 2 Issue 1 Pages 390-394
Background: Small intestinal bacterial overgrowth (SIBO) can present not only with gastrointestin al symptoms but also with psychiatric symptoms mediated by deficiencies of iron, zinc, and vitam in D; therefore, understanding this disease concept is clinically important.
Case: A 42-year-old woman experienced abdominal pain, postprandial bloating, and constipation fo r one year, accompanied by insomnia and depressive mood. Extensive examinations revealed no or ganic abnormalities. At the initial visit, serum ferritin was 7 ng/mL, zinc 74 μg/dL, and 25-hydro xyvitamin D 15.6 ng/mL. A low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet was introduced, an H2-receptor antagonist was discontinued, and ursodeox ycholic acid 600 mg/day was initiated. Intravenous ferric carboxymaltose 500mg , twice a day, po laprezinc 150 mg/day, and vitamin D 2,000 IU/day were added. Gastrointestinal symptoms improv ed first, followed by resolution of insomnia and depressive mood within approximately six month s, with improvement in ferritin to 55 ng/mL, zinc to 84 μg/dL, and 25-hydroxyvitamin D to 31.5 ng/mL.
Conclusion: In patients with gastrointestinal symptoms accompanied by psychiatric symptoms, cons idering SIBO in the differential diagnosis and evaluating nutritional parameters may be important, and nutritional psychiatry–based interventions including dietary modification and correction of defic iencies may be clinically beneficial.
