Metabolic Interrelationship between Vitamin B₁₂ and Ascorbic Acid in Pernicious Anemia

An interrelationship between vitamin C and vitamin B₁₂ was studied in three patients with vitamin B₁₂ deficiency associated with pernicious anemia. Subnormal plasma ascorbate concentrations were found prior to therapy confirming previous observations. Following vitamin B₁₂ administration and utilizing methylmalonate (MMA) excretion as a biochemical index of vitamin B₁₂ deficiency, low plasma ascorbate concentrations persisted until MMA excretion was abolished. In two patients, RBC vitamin B₁₂ activity was also serially measured in order to evaluate its sensitivity as an index of vitamin B₁₂ stores when compared to MMA excretion. The data demonstrate that in these two vitamin B₁₂-deficient patients undergoing slow repletion therapy, RBC vitamin B₁₂ activity returns to normal before MMA excretion is abolished.

Whether continued MMA excretion in these patients indicates a greater sensitivity of MMA excretion as an index of deficiency of vitamin B₁₂ stores than does RBC vitamin B₁₂ activity remains to be answered by future work.