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 < 0.001 and P < 0.001 for MMA and P = 0.03 and P = 0.045 for Hcy, respectively). There was no significant difference between the groups at 6 mo for both MMA and Hcy (P = 0.53 and P = 0.79). The efficacy of oral vitamin B-12 supplementation was similar to that of hydroxocobalamin injections in the present study. Oral supplementation can be used as an alternative to hydroxocobalamin injections to treat RYGB patients with low values of serum vitamin B-12. This trial was registered at clinicaltrials.gov as NCT02270749.