Biliary and Fecal Vit. B 12 Excretion in Man. An Isotope Study. ∗

Abstract

Summary

It was attempted to study Vit. B₁₂ excretion in man by investigating the elimination of small doses of parenterally administered radiovitamin Co⁵⁶-B₁₂. Relatively large amounts of radioactivity were excreted in the bile, feces and urine shortly after injection. After this period, the excretion pattern changed, and radioactivity of relatively constant value was excreted with the bile and feces, indicating that these are the main excretion routes in man, whereas the urine samples exhibited low radioactivity. The fecal radioactivity was only about one-third of the calculated biliary excretion, which indicates intestinal reabsorption of biliary B₁₂. If it were assumed, that the radiovitamin mixes uniformly with the body stores of Vit. B₁₂, it could be estimated that normal subjects may lose considerable amounts of B₁₂ per day, and consequently, the requirement of B₁₂ could be larger than hitherto suspected. The findings may have therapeutical implications.