Antibiotic Therapy Reverses Thiamine Deficiency in Patients Following Roux-en-Y Gastric Bypass Surgery

Abstract

Purpose: As standard-of-care, all patients receive daily vitamin/mineral supplements following gastric bypass surgery. Present dogma states that thiamine deficiency after gastric bypass surgery is caused by prolonged nausea and emesis. We previously reported that a majority of patients following Roux-en-Y gastric bypass surgery have thiamine deficiency and it is associated with high serum folate levels and abnormal glucose-hydrogen breath tests. We hypothesize that small bowel bacterial overgrowth is a mechanism for thiamine deficiency following gastric bypass surgery. Methods: This is a retrospective chart review of patients who had Roux-en-Y gastric bypass surgery in 1999–2005. This study included: 1) post-operative patients who had whole blood thiamine levels below the lower limit of normal; 2) who then underwent a glucose-hydrogen breath test. Patients' sex, age, blood thiamine levels after oral thiamine supplementation, and blood thiamine levels after antibiotic therapy were recorded. Abnormal glucose-hydrogen breath test was defined by increased breath hydrogen of >20 ppm within 45 minutes after 50 grams oral glucose. This study involved 17 females and 4 males; age range was 22–64 years (Mean age: 52 years). Results: 21 patients (100%) with low blood thiamine had an abnormal glucose-hydrogen breath test. Of these patients, 15 received oral thiamine (100 mg twice daily); repeat thiamine levels remained low in all 15 (100%). Of these patients, 8 then received oral metronidazole while 1 received oral amoxicillin in addition to thiamine (100 mg twice daily); repeat blood thiamine levels were normal in all 9 (100%). While taking daily oral thiamine supplements, 2 patients who stopped taking metronidazole on a cycle of 7–10 days monthly had repeat thiamine levels drawn that were again low. Conclusions: After gastric bypass surgery, patients with thiamine deficiency have evidence for small bowel bacterial overgrowth. Daily oral thiamine supplements do not appear effective for treating thiamine deficiency. Antibiotic therapy combined with oral thiamine supplements was effective for treating thiamine deficiency. This study supports our hypothesis that small bowel bacterial overgrowth interferes with thiamine absorption from small intestine. Overgrowth may result from an absence of gastric acid secretion.