The vitamin C requirements of man

Abstract

The level of urinary excretion of ascorbic acid on a given dose was lower after ascending from a condition of "unsaturation," or from a condition of "saturation" reached on a lower dose, than after "saturation" with a higher dose. The equilibrium in the excretion of a 184-lb. subject was established on daily doses of 30, 50 and 100 mg.; with 30 mg. the excretion of ascorbic acid almost ceased and the minimum "saturation" dose probably lay near this figure. Although the "saturation" dose was the minimum vit. C daily intake to be recommended for normal individuals, about half this dose was sufficient to prevent scurvy and maintain good health. Comparison of the urinary ascorbic acid with that of the blood in 2 individuals during "saturation" and "unsaturation" at different intervals after various doses suggested that there was no constant renal threshold for ascorbic acid, but a competition for the ascorbic acid of the blood by the absorptive capacity of the tissues and the excreting function of the kidney. Blood levels detd. at random did not indicate the degree of "saturation" of a subject.