Comparative Absorption of Vitamin B12 Analogues by Normal Humans. I. Chlorocobalamin vs. Cyanocobalamin

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Abstract
Urinary excretion tests were performed with Co60 labeled cobalamin by the method of Schilling under carefully controlled conditions and with volunteers with comparable dietary history and age. It was found that the amount of radioactivity in the urine of a group of subjects receiving chlorocobalamin is considerably less than that in the urine of a comparable group of young adult males receiving 2 [mu]g of cyanobalamin orally. The differences in the radioactivity in the urine specimens are attributed either to absorption or to tissue retention or both. The importance in the electrolyte nature and attendent solubility properties in relationship to the urinary excretion is discussed.