Background: Vitamin B
12 deficiency after gastric surgery for obesity is due to a failure of separation of vitamin B
12 from protein foodstuffs and to a failure of absorption of crystalline vitamin B
12 in the presence of intrinsic factor. The purpose of this study was to determine which of four oral doses of crystalline vitamin
B
12 was most effective in treating vitamin B
12 deficiency in 102 patients. Methods and Results: At time of entry into the study, the patients had a serum vitamin B
12 < 100 pmol L
−1, were 29.9 ± 21.7 months post-op, were 37 ± 8 years old and had a body mass index of 30 ± 6 kg m
−2. Eight (8%) had had a vertical banded gastroplasty and 94 (92%) a gastric bypass. For the first 3 months all patients received
350 μg per day of crystalline vitamin B
12 and all increased their serum vitamin B
12 levels to over 100 pmol L
−1. The patients were then assigned to receive for a further 3 month period one of four oral doses of crystalline vitamin B
12-100 μg, 250 μg, 350 μg and 600 μg. Serum vitamin B
12 levels were greater than 150 pmol L
−1 after 6 months in 83.3% of patients who received 100 μg; 92.3% of patients who received 250 μg; 94.7% after 350 μg and 95.2%
after 600 μg (
p%0.525). Conclusion: At least 350 μg per day is the appropriate oral dose of crystalline vitamin B
12 after gastric surgery for obesity to correct low serum vitamin B
12 levels in 95% of patients.
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