The recently released Recommended Dietary Allowance of vitamin C for women, 75 mg daily, was based on data for men. We now report results of a depletion-repletion study with healthy young women hospitalized for 186 +/- 28 days, using vitamin C doses of 30-2,500 mg daily. The relationship between dose and steady-state plasma concentration was sigmoidal. Only doses above 100 mg were beyond the linear portion of the curve. Plasma and circulating cells saturated at 400 mg daily, with urinary elimination of higher doses. Biomarkers of endogenous oxidant stress, plasma and urine F(2)-isoprostanes, and urine levels of a major metabolite of F(2)-isoprostanes were unchanged by vitamin C at all doses, suggesting this vitamin does not alter endogenous lipid peroxidation in healthy young women. By using Food and Nutrition Board guidelines, the data indicate that the Recommended Dietary Allowance for young women should be increased to 90 mg daily.