Efficacy of oral compared with intramuscular vitamin B-12 supplementation after Roux-en-Y gastric bypass: a randomized controlled trial

After Roux-en-Y gastric bypass (RYGB), patients often develop a vitamin B-12 deficiency. Our objective was to investigate whether oral supplementation increases and normalizes low vitamin B-12 concentrations (vitamin B-12 > 200 pmol/L) in RYGB patients as compared to intramuscular injections. A randomized controlled trial in RYGB patients with subnormal serum B-12 concentrations was performed. One group (IM B-12) received bimonthly intramuscular hydroxocobalamin injections (2000 µg as loading dose and 1000 µg at follow-up) for 6 mo. The second group (oral B-12) received daily doses of oral methylcobalamin (1000 µg). Serum vitamin B-12 was determined at baseline (T0) and at 2 (T1), 4 (T2), and 6 mo (T3) after start of treatment. Concentrations of the secondary markers methylmalonic acid (MMA) and homocysteine (Hcy) were measured at T0 and T3. Fifty patients were included and randomized, 27 in IM B-12 and 23 in oral B-12. The median vitamin B-12 concentration at T0 was 175 pmol/L (range: 114–196 pmol/L) for IM B-12 and 167 pmol/L (range: 129–199 pmol/L) for oral B-12. Vitamin B-12 normalized in all individuals, and there was no significant difference in vitamin B-12 between the two groups. MMA and Hcy concentrations decreased significantly after 6 mo within each group (P