VITAMIN-B-12 DEFICIENCY AFTER GASTRIC-SURGERY FOR OBESITY

Low serum vitamin B-12 concentrations after gastric bypass (GB) surger y for obesity were observed in 11 of 28 patients without detectable im pairment 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 demon strated in eight of these patients after GB (n = 7) and VBG (n = 1). C orrection of this impaired absorption occurred when protein-bound vita min B-12 was incubated with an enzyme mixture before consumption. Simu ltaneous 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 c orrect low serum vitamin B-12 concentrations with a quantity of oral c rystalline vitamin B-12 equal to the recommended dietary allowance of 2 mu g, taken twice daily for 3 mo. Serum total homocysteine values de clined during this interval. An oral daily dose of 350 mu g crystallin e vitamin B-12 raised the average serum vitamin B-12 concentration to an amount greater than the lower reference limit. A dose > 350 mu g/d was required to raise all patients' vitamin B-12 concentrations above this concentration rather than just above the population mean. We conc lude that because concentrations of oral crystalline vitamin B-12 were required to normalize serum vitamin B-12 concentrations, that a mecha nism other than formation of a vitamin B-12 intrinsic factor complex i s responsible for crystalline vitamin B-12 absorption after GB for obe sity.