Sequelae to the Administration of Vitamin B12 to Humans

Abstract

In confirmation of our previous reports, it was found that oral administration of vitamin B₁₂ over a period of several months or in a single massive dose (5.0 mg per adult) did not result in the appearance of vitamin B₁₂ activity in the urine. A major portion of the ingested vitamin appeared in the feces. These results indicate poor but apparently adequate absorption of the vitamin in the gastrointestinal tract, even in clinically healthy individuals. When vitamin B₁₂ was given intravenously to man, the blood level decreased rapidly and the administered vitamin could be recovered in the urine. Determinations of vitamin B₁₂ in plasma and blood failed to yield evidence of penetration into or adsorption onto the erythrocytes within 15 minutes in vivo. This was further substantiated in in vitro studies, where no appreciable activity could be detected in the red cells obtained from defibrinated human blood previously incubated with vitamin B₁₂ for three hours. The vitamin was completely recovered in the plasma. When B₁₂ was given parenterally to infants fed on a soybean protein diet, no increase in nitrogen retention was observed. Observations on the effect of vitamin B₁₂ on the weight gain of chronically ill and clinically healthy children were made. Data have been presented to show that children of either type gained greater weight than the corresponding controls if offered B₁₂ supplementation in a given period. However, due to the heterogeneity of the subjects with chronic illness and the small numbers of the normal children studied, the results are merely considered suggestive of trends which may be confirmed by extended observations under even better controlled conditions.