Vitamin C is an essential water soluble vitamin. To date there have been no carefully controlled clinical trials to demonstrate how changes in vitamin C concentration in human plasma vary as a direct function of the amount ingested over a wide range. In this study, we plan to achieve a prescorbutic vitamin C plasma concentration of approximately 12-15 micromolar in thirteen healthy human volunteers and gradually replete these subjects with incremental doses of vitamin C to measure how their plasma concentrations will change as a function of the dose.

We will induce vitamin C deficiency in the outpatient setting by having volunteers adhere to a vitamin C restricted diet. As inpatients they will be placed on a more tightly restricted scorbutic diet. Plasma vitamin C will be monitored several times per week. When subjects have achieved a plasma AA concentration of 12-15 micromolar, blood sampling and urine collection over 24 hours will be performed. After platelets and leukocytes are collected, AA repletion will begin. Escalating doses of AA will be administered orally and intravenously for the remainder of their inpatient admission. Total daily doses of 30mg, 60mg, 100mg, 200mg, 400mg, 1000mg and 2500mg will be given in two divided doses. Bioavailability of AA will be determined at each dosage increment. When plasma AA concentration reaches steady state for each dose, subjects will undergo 36 hr plasma AA sampling and a timed 48 hr urine collection. At steady state of each of 4 to 5 doses, an apheresis procedure will be performed for collection of platelets and leukocytes. It is anticipated subjects will be discharged in healthy condition after 18 weeks.