The Urinary Excretion Test for Absorption of Vitamin B12

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Abstract
A urinary excretion test using radioactive vitamin B12 was applied to a group of young male adults with similar dietary histories and living conditions and under conditions which minimize errors in urine collections, as well as to a group of ambulatory elderly individuals. The variation of the results obtained from this group of normal subjects and the reproducibility of the tests performed on the same individuals are presented. The results failed to reveal a significant variation of absorption with age. Of interest is the small incidence of low absorption in the aged group. It is not certain to what extent these measurements represent true absorption, since urinary excretion of orally administered vitamin B12 may be influenced by tissue retention and kidney function. The simultaneous administration of intrinsic factor concentrates to subjects without pernicious anemia does not appear to enhance the absorption of vitamin B12. Variations observed were not greater than the normal variation exhibited by a given subject.