American Journal of Clinical Nutrition, Vol 25, 395-400, Copyright © 1972 by The American Society for Clinical Nutrition, Inc.

The long-term relationship between serum vitamin B₁₂ and total body vitamin B₁₂

¹ Senior Lecturer (Health Physics and Nuclear Medicine), Scottish Universities Research Reactor Centre, East Kilbride, Glasgow, Scotland
² Consultant Physician, Southern General Hospital, Glasgow, S.W.1

Following parenteral administration of large doses of labeled vitamin B₁₂, the long-term rate of loss of the vitamin from the whole body and from the serum were measured, mainly in patients with pernicious anemia. In each patient, these rates of loss could be adequately described by a single exponential term and, in 11 of the 15 patients, the rate of loss from the body was not significantly different from the rate of loss from the serum.

The retained dose was effectively the total body vitamin B₁₂ and was shown to be significantly correlated with the serum vitamin B₁₂, with the exception of two patients in whom disparities could be demonstrated. From these data, the pretreatment total body content of vitamin B₁₂ was estimated in each patient. In the patients suffering from pernicious anemia, the total body content ranged from 41 to 135 µg, with only two values being greater than 84 µg. In two patients who had previously undergone partial gastrectomy, the estimated total body vitamin B₁₂ was 210 and 318 µg and in a subject with an irrelevant disease it was 650 µg. Although the total body vitamin B₁₂ (micrograms)/serum vitamin B₁₂ (picograms per milliliter), or the K value, was constant in individual subjects, this ratio varied widely from one individual to another. The K value was significantly smaller in the present patients than in control subjects. Finally, the mean rate of loss from the body and from the serum vitamin B₁₂ was apparently independent of the analog form in which the vitamin was administered.