Biliary and fecal vit. B12 excretion in man: an isotope study.

Abstract

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.