Small Bowel Bacterial Overgrowth Is a Potential Mechanism for Thiamine Deficiency Identified after Roux-En-Y Gastric Bypass Surgery

Abstract

Purpose: Present evidence supports a saturable, carrier-mediated exchange mechanism for thiamine transport across jejunum. It is proposed that thiamine deficiency after gastric bypass surgery results from prolonged nausea and emesis. We observed that individuals after gastric bypass surgery developed thiamine deficiency and elevation of serum folate levels, a proposed marker for small bowel bacterial overgrowth. We hypothesized that small bowel bacterial overgrowth interferes with absorption of thiamine from the small intestine. Methods: We performed a retrospective review of consecutive patients who underwent Roux-en-Y gastric bypass surgery from 2002–2004 in our institution. To eliminate immediate, post-operative changes, we included patients who received evaluation at 3 months or longer after surgery. There were 75 patients with determination of serum thiamine and folate levels. This included 48 females and 27 males with an average age of 46 years (range 21 to 68). Five patients with low serum thiamine and elevated serum folate levels had undergone glucose-hydrogen breath testing. Results: There were 37 patients with serum folate levels greater than the upper limit of normal; among these patients, 23 (62%) had serum thiamine levels below the lower limit of normal. There were 38 patients with serum folate levels within normal range; 11 (29%) had serum thiamine levels below the lower limit of normal (Chi-squared test comparing thiamine deficiency in the normal folate group to the elevated folate group: p< .01). All 5 patients who underwent glucose-hydrogen breath testing had abnormal findings supporting a diagnosis of small bowel bacterial overgrowth: 4 patients had a significant rise (>10 ppm) in breath hydrogen within 45 minutes after glucose ingestion, while 1 had an elevated fasting breath hydrogen level of 57 ppm. Conclusions: Thiamine deficiency is common after Roux-en-Y gastric bypass surgery. Small bowel bacterial overgrowth appears to be common after gastric bypass surgery, as determined by elevation of serum folate levels or the presence of abnormal glucose-hydrogen breath testing. The results support the hypothesis that small bowel bacterial overgrowth following gastric bypass surgery can interfere with thiamine absorption.