The influence of serum folate on urinary excretion of vitamin B12

It was found that in patients with decreased serum folate concentration, urinary excretion of vitamin B₁₂ was increased in a statistically highly significant way with both oral administration of ⁵⁸Co-labeled vitamin B₁₂ and with a ⁵⁷Co-labeled vitamin B₁₂ intrinsic factor complex. This increased vitamin B₁₂ excretion may account for some false normal Schilling test results.Furthermore, in folate deficiency, the intrinsic factor no longer seems required for vitamin B₁₂ to pass the intestinal wall. It is also questionable whether vitamin B₁₂ absorbed through the intestine under these circumstances could be properly metabolized.Besides statistical evidence, some clinical support for this theory is presented. These findings offer a possible clue for some literature reports that have lacked a satisfactory explanation.