Metabolic interrelationship between vitamin B12 and ascorbic acid in pernicious anemia.

S UBNORMAL PLASMA ascorbic acid concentration and rapid plasma ascorbate clearance have been found in patients with vitamin B12 deficiency despite adequate intake of vitamin C. 2 Cox et al.2 noted in their group of vitamin B12-deficient patients that these abnormalities of ascorbate metabolism were still present 7-14 days following therapy with sufficient vitamin B12 to cause clinical and hematological response. Prolonged vitamin B12 therapy was necessary before ascorbate metabolism returned to normal.2 Recently we described a patient with scurvy and anemia in whom, during therapy with vitamin C, methylmalonate (MMA) excretion was detected.3 At this time, the hemoglobin concentration was rapidly rising but the plasma vitamin B12 activity was normal. It was speculated that MMA excretion suggested depletion of body vitamin B12 stores, since therapy with vitamin B12 caused abolition of MMA excretion.4’5 In this patient despite long term administration of high doses of vitamin C, the plasma ascorbate concentration did not become normal until MMA excretion was abolished.3 These data suggested that the plasma ascorbate concentration is related to the excretion of MMA and is directly or indirectly related to vitamin B12 stores.