Effect of 8-week oral supplementation with 3-µg cyano-B12 or hydroxo-B12 in a vitamin B12-deficient population

PURPOSE: We compare the effect of 8-week oral supplementation with cyano-B12 (currently used in vitamin pills) and hydroxo-B12 (predominant form in the diet) in a population with nutritional vitamin B12 deficiency. METHODS: Fifty-one healthy Indian adults with baseline serum cobalamin < 200 pmol/L were supplied for 8 weeks with daily oral supplements of 3-µg cyano-B12 (n = 15), 3-µg hydroxo-B12 (n = 16), or a placebo (n = 20). Blood at baseline, and each following week, was examined for total cobalamin, holotranscobalamin, methylmalonic acid, and homocysteine. RESULTS: The study groups did not differ at baseline and were characterized by [median (range)] serum cobalamin [128 (68–191) pmol/L], holotranscobalamin [16 (6–41) pmol/L], methylmalonic acid [0.8 (0.3–1.7) µmol/L], homocysteine [17.9 (8.5–100.9) µmol/L], and a combined indicator of B12 status 4cB12 of − 1.65 (− 0.64 to − 4.07). The group supplemented with cyano-B12 showed a higher increase in total serum cobalamin than the group treated with hydroxo-B12, while other biomarkers changed comparably in the two groups. After 8 weeks of treatment, the biomarker values of the supplemented groups (pooled) differed significantly from the placebo group. Yet, the vitamin B12 status was still poor [cobalamin: 168 (87–302) pmol/L; holotranscobalamin: 19 (8–45) pmol/L; methylmalonic acid: 0.7 (0.2–1.7) µmol/L; homocysteine: 17.2 (2.6–96.8) µmol/L; 4cB12 = − 1.34 (− 0.33 to − 3.3)]. CONCLUSION: 8-week supplementation with 3-µg cyano-B12 elevated serum cobalamin more than 3 µg hydroxo-B12, but all other biomarkers changed similarly in both groups. Supplementation with 3 µg vitamin B12 did not reverse the low status in individuals with nutritional vitamin B12 deficiency. CLINICAL TRIAL REGISTRY OF INDIA: REF/2017/02/013343. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00394-017-1590-0) contains supplementary material, which is available to authorized users.