title: Vitamin B-12 deficiency after gastric surgery for obesity.
abstract: Low serum vitamin B-12 concentrations after gastric bypass (GB) surgery for obesity were observed in 11 of 28 patients without detectable impairment of crystalline vitamin B-12 absorption. This was observed in 2 of 19 patients with vertical banded gastroplasty (VBG). In contrast, protein-bound vitamin B-12 absorption was markedly impaired, as demonstrated in eight of these patients after GB (n = 7) and VBG (n = 1). Correction of this impaired absorption occurred when protein-bound vitamin B-12 was incubated with an enzyme mixture before consumption. Simultaneous ingestion of the enzyme mixture with protein-bound vitamin B-12 did not improve absorption of the vitamin. In a separate experiment, 10 patients with a normal result from the Schilling test failed to correct low serum vitamin B-12 concentrations with a quantity of oral crystalline vitamin B-12 equal to the recommended dietary allowance of 2 micrograms, taken twice daily for 3 mo. Serum total homocysteine values declined during this interval. An oral daily dose of 350 micrograms crystalline vitamin B-12 raised the average serum vitamin B-12 concentration to an amount greater than the lower reference limit. A dose > 350 micrograms/d was required to raise all patients' vitamin B-12 concentrations above this concentration rather than just above the population mean. We conclude that because concentrations of oral crystalline vitamin B-12 were required to normalize serum vitamin B-12 concentrations, that a mechanism other than formation of a vitamin B-12 intrinsic factor complex is responsible for crystalline vitamin B-12 absorption after GB for obesity.
authors.affiliation: Department of Surgery, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada.
authors.forename: B M
authors.initials: BM
authors.lastname: Rhode
authors.forename: P
authors.initials: P
authors.lastname: Arseneau
authors.forename: B A
authors.initials: BA
authors.lastname: Cooper
authors.forename: M
authors.initials: M
authors.lastname: Katz
authors.forename: B M
authors.initials: BM
authors.lastname: Gilfix
authors.forename: L D
authors.initials: LD
authors.lastname: MacLean
mesh_terms: D000328:Adult; D000713:Anastomosis, Roux-en-Y; D005260:Female; D015390:Gastric Bypass / Q000009:adverse effects*; D015391:Gastroplasty / Q000009:adverse effects*; D006710:Homocysteine / Q000097:blood; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D009767:Obesity, Morbid / Q000097:blood / Q000601:surgery*; D014805:Vitamin B 12 / Q000097:blood / Q000493:pharmacokinetics; D014806:Vitamin B 12 Deficiency / Q000097:blood / Q000209:etiology*
chemical_list: D006710:Homocysteine; D014805:Vitamin B 12