Production of Vitamin B12 Analogues in Patients with Small-Bowel Bacterial Overgrowth

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Abstract
The presence of vitamin B12 analogues (cobamides) and bacterial conversion of 57Co-B12 (vitamin B12 cyanocobalamin, [57Co]-CN-Cbl) into cobamides in intestinal contents of 4 patients with bacterial overgrowth were investigated. The (57Co)-CN-Cbl bound to intrinsic factor was given orally. Jejunal contents were aspirated for 24 h and cultured aerobically and anaerobically. The CN-Cbl and cobamides were separated by electrophoresis and chromatography and identified by bioautography. Radioactivity of cobamide zones from duplicate chromatograms showed bacterial conversion of (57Co)-CN-Cbl into cobamides. Cobamides ([Ade]CNCba, [2-Me Ade] CNCba, [CN]2Cbi and factor E) were found in intestinal contents in 3 of 4 patients, and in 2 of 3 patients cobamides represented more than 25% of administered CN-Cbl. Bacterial production of cobamides, de novo and from ingested CN-Cbl bound to intrinsic factor, occurs in humans with bacterial overgrowth states and results in a significant loss of vitamin B12 to the host.