Vitamin C supplementation of total parenteral nutrition formulas.

The effect of a wide range of daily vitamin C intake (350-2250 mg, mean 975 mg) on the serum and urine vitamin C levels was studied in 20 adult hospitalized patients receiving total parenteral nutrition for a period greater than 15 days. Serum vitamin C levels increased with vitamin C administration, but remained within the normal range. Urine vitamin C levels were above normal during total parenteral nutrition in all but one patient. A positive vitamin C "balance" was achieved in all patients. The vitamin C intake positively correlated with the vitamin C urine concentration and vitamin C "balance." Maximal vitamin C retention was 800 mg/day. It is concluded that administration of vitamin C in doses greater than 1000 mg/day is unjustified in those patients receiving total parenteral nutrition who are not hypermetabolic.