Metabolism of Ascorbic-1-14C Acid in Experimental Human Scurvy

Abstract

A study of the metabolism of ascorbic-l-¹⁴C acid in experimental human scurvy was conducted with the following results: 1) Labeling the body ascorbic acid pool during the depletion phase resulted in no detectable urinary excretion of ¹⁴C-labeled reduced ascorbic acid or dehydroascorbic acid. 2) Urinary excretion of ¹⁴C by all subjects occurred as a first order process during the depletion phase. The urinary ¹⁴C excretion curves of the four subjects did not differ from the average man by more than ± 3%, despite marked differences in body weight and age. 3) First symptoms of mild scurvy appeared in the subjects when their body ascorbic acid pool had been reduced to approximately 300 mg. 4) Once the body pool of ascorbic acid was repleted to a level of 1.5 g, urinary loss of reduced ascorbic acid occurred. 5) The rate of repletion of ascorbic acid was found to be a zero-order process and proportional to the level of daily ascorbic acid intake. 6) When the subjects were fed a high intake of ascorbic acid, only a limited quantity of the ingested vitamin was equilibrated with the ¹⁴C-labeled ascorbate pool. 7) All of the radioactivity excreted during the depletion phase was in the form of stable organic material that did not behave as ascorbic acid. This organic material was separated into four unknown compounds. 8) The daily intake of 6.5 mg/day of ascorbic acid was sufficient to alleviate and cure the clinical signs of scurvy in one man.