USE OF A NEW VITAMIN-C-DEFICIENT DIET IN A DEPLETION-REPLETION CLINICAL-TRIAL

To conduct an inpatient study on the recommended dietary allowance (RD A) for vitamin C, we developed a unique vitamin C-deficient diet using a nutrient database and selective menus. Fourteen different menus wer e developed offering > 300 items with 0-2.4 mg vitamin C per serving. During the 4-6 mo volunteers were hospitalized, daily dietary vitamin C was restricted to less than or equal to 5.0 mg. The mean daily dieta ry vitamin C intake was < 3.9 mg for the seven study subjects. With co ncurrent supplementation, the diet provided greater than or equal to 8 5% of the RDA for 17 essential nutrients. Within 3 wk of admission the diet induced vitamin C deficiency as indicated by plasma concentratio ns, which decreased from 23 +/- 6.9 to 6.9 +/- 2.0 mu mol/L. Daily int ake of vitamin C and five other nutrients was determined by nutrient d atabase analyses. Mean energy, protein, and iron were 105-185% of the RDA and total and saturated fat were 32% and 10% of energy, respective ly. Weight and nutritionally relevant indexes remained normal. Dietary adherence, calculated by the number of days with less than or equal t o 5.0 mg vitamin C per total study days, was 88-98% per repletion dose . Computer analyses of menu selections permitted individual preference s to be met while restricting vitamin C intake to less than or equal t o 5.0 mg/d. There were no complications from the diet during the deple tion and repletion phases. With this diet, ascorbic acid pharmacokinet ics for escalating doses could be determined in healthy volunteers.