Comparative Bioavailability of Synthetic B12 and Dietary Vitamin B12 Present in Cow and Buffalo Milk: A Prospective Study in Lactovegetarian Indians.

We assessed improvements in the vitamin B12 status of Indian lactovegetarians receiving four weeks supplementation with natural B12 in milk versus cyano-B12 in capsules. Three groups ( = 22, 23, 22) received daily oral doses of cyano-B12 (2 × 0.76 µg) or milk (2 × 200 mL) from a cow or buffalo (amounting to B12 ≈ 2 × 0.76 µg). Their blood was examined at baseline and each following week. The baselines (median (min/max)) indicated a low B12 status: plasma B12 (116(51/314)) pmol/L, holotranscobalamin (holoTC) (30(7/119)) pmol/L, total homocysteine (Hcy) (24(10/118)) µmol/L, methylmalonic acid (MMA) (0.58(0.15/2.2)) µmol/L and combined B12 index (cB12) (-1.32 - (-3.12/+0.29)). Shifts from the baselines (B12, holoTC, cB12) and ratios to the baselines (Hcy, MMA) were analyzed over time. The cyano-B12 treatment gave more total B12 in plasma at week one (+29 pmol/L, = 0.004) but showed no further increase. Other biomarkers changed more comparably between the three groups ( ≥ 0.05): holoTC showed a transient spike that leveled off, Hcy finally decreased to 0.8 × baseline, while MMA showed marginal changes. The combined indexes improved comparably ( = 0.6) in all groups (+0.2(-0.3/+0.9), ≤ 0.002). In conclusion, the tested formulations similarly improved B12 status, but did not normalize it.